# Determine if a string is numeric

(Redirected from IsNumeric)
Determine if a string is numeric
You are encouraged to solve this task according to the task description, using any language you may know.

Create a boolean function which takes in a string and tells whether it is a numeric string (floating point and negative numbers included) in the syntax the language uses for numeric literals or numbers converted from strings.

## 6502 Assembly

For this program, a valid numeric string literal consists of only numbers (ascii $30-$39), up to one leading minus sign, and no more than one decimal point. Anything else, including the null string, is considered non-numeric.

Macros used (VASM syntax):


sta \regs
sta \regs+1
endm

macro pushY
tya
pha
endm

macro popY
pla
tay
endm


The code:

*=$0801 db$0E,$08,$0A,$00,$9E,$20,$28,$32,$30,$36,$34,$29,$00,$00,$00  ;required init code on commodore 64 floppy disks
*=$0810 lda #$0e
jsr chrout ;required for my printing routine to work.

z_HL equ $02 z_L equ$02
z_H  equ $03 z_B equ$04

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

jsr isStringNumeric

isStringNumeric:
; input: z_HL = source address
pushY
ldy #0
sty z_B		;our tally for decimal points

checkFirstChar:
lda (z_HL),y
beq notNumeric			;a null string is not a valid number!
cmp #'-'
beq isNegative_OK
cmp #'.'
beq isFloat_OK
and #$30 cmp #$30
beq isNumeral_OK
;else, is not numeric
notNumeric:
popY
jsr PrintString_TextScreen	;prints what's already in z_HL
jsr NewLine
jsr PrintString_TextScreen
jsr NewLine
jmp NewLine
;rts
isNegative_OK:
isNumeral_OK:
iny
jmp loop_isStringNumeric
isFloat_OK:
iny
inc z_B
loop_isStringNumeric:
lda (z_HL),y
beq Terminated_isStringNumeric
cmp #'.'
and #$30 cmp #$30
bne notNumeric
iny
jmp loop_isStringNumeric

lda z_B
bne notNumeric
inc z_B

Terminated_isStringNumeric:
;if we got this far the string is numeric.
popY
jsr PrintString_TextScreen	;prints what's already in z_HL
jsr NewLine
jsr PrintString_TextScreen
jsr NewLine
jmp NewLine
;rts

isStringNumeric_Pass:
db "IS NUMERIC",0
isStringNumeric_Fail:
db "IS NOT NUMERIC",0

TestString0:
db 0
TestString1:
db "123",0
TestString2:
db "-30",0
TestString3:
db "123.45",0
TestString4:
db "-123.45",0
TestString5:
db "ABCDE",0
TestString6:
db "-34-5",0
TestString7:
db "1.000.000",0
TestString8:
db ".23456",0
Output:
ready.

searching for *
run

IS NOT NUMERIC

123
IS NUMERIC

-30
IS NUMERIC

123.45
IS NUMERIC

-123.45
IS NUMERIC

ABCDE
IS NOT NUMERIC

-34-5
IS NOT NUMERIC

1.000.000
IS NOT NUMERIC

.23456
IS NUMERIC



## 8th

: number? >n >kind ns:n n:= ;


## AArch64 Assembly

Works with: as version Raspberry Pi 3B version Buster 64 bits
/* ARM assembly Raspberry PI  */
/*  program strNumber.s   */

/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"

.equ BUFFERSIZE,          100

/* Initialized data */
.data
szMessNum: .asciz "Enter number : \n"

szMessError:            .asciz "String is not a number !!!\n"
szMessInteger:          .asciz "String is a integer.\n"
szMessFloat:            .asciz "String is a float.\n"
szMessFloatExp:         .asciz "String is a float with exposant.\n"
szCarriageReturn:       .asciz "\n"

/* UnInitialized data */
.bss
sBuffer:              .skip BUFFERSIZE

/*  code section */
.text
.global main
main:

loop:
bl affichageMess
mov x0,#STDIN                               // Linux input console
mov x2,#BUFFERSIZE                          // buffer size
svc 0                                       // call system
mov x2,#0                                   // end of string
sub x0,x0,#1                                   // replace character 0xA
strb w2,[x1,x0]                             // store byte at the end of input string (x0 contains number of characters)
bl controlNumber                            // call routine
cmp x0,#0
bne 1f
ldr x0,qAdrszMessError                      // not a number
bl affichageMess
b 5f
1:
cmp x0,#1
bne 2f
bl affichageMess
b 5f
2:
cmp x0,#2
bne 3f
bl affichageMess
b 5f
3:
cmp x0,#3
bne 5f
ldr x0,qAdrszMessFloatExp                   // float with exposant
bl affichageMess
5:
b loop

100:                                            // standard end of the program
mov x0, #0                                  // return code
mov x8, #EXIT                               // request to exit program
svc 0                                       // perform system call
/******************************************************************/
/*     control if string is number                          */
/******************************************************************/
/* x0 contains the address of the string */
/* x0 return 0 if not a number       */
/* x0 return 1 if integer   eq 12345 or -12345      */
/* x0 return 2 if float     eq 123.45 or 123,45  or -123,45     */
/* x0 return 3 if float with exposant  eq 123.45E30 or -123,45E-30        */
controlNumber:
stp x1,lr,[sp,-16]!    // save  registers
stp x2,x3,[sp,-16]!    // save  registers
stp x4,x5,[sp,-16]!    // save  registers
mov x1,#0
mov x3,#0              // point counter
1:
ldrb w2,[x0,x1]
cmp x2,#0              // end string ?
beq 7f
cmp x2,#' '            // space ?
bne 3f
b   1b                 // loop
3:
cmp x2,#'-'            // negative ?
bne 4f
b 5f
4:
cmp x2,#'+'            // positive ?
bne 5f
5:
ldrb w2,[x0,x1]        // control space
cmp x2,#0              // end ?
beq 7f
cmp x2,#' '            // space ?
bne 6f
b 5b                   // loop
6:
ldrb w2,[x0,x1]
cmp x2,#0              // end ?
beq 14f
cmp x2,#'E'            // exposant ?
beq 9f
cmp x2,#'e'            // exposant ?
beq 9f
cmp x2,#'.'            // point ?
bne 7f
add x3,x3,#1           // yes increment counter
b 6b                   // and loop
7:
cmp x2,#','            // comma ?
bne 8f
add x3,x3,#1           // yes increment counter
b 6b                   // and loop
8:
cmp x2,#'0'            // control digit < 0
blt 99f
cmp x2,#'9'            // control digit > 0
bgt 99f
add x1,x1,#1           // no error loop digit
b 6b

9:                         // float with exposant
ldrb w2,[x0,x1]
cmp x2,#0              // end ?
beq 99f

cmp x2,#'-'            // negative exposant ?
bne 10f
10:
mov x4,#0              // nombre de chiffres
11:
ldrb w2,[x0,x1]
cmp x2,#0              // end ?
beq 13f
cmp x2,#'0'            // control digit < 0
blt 99f
cmp x2,#'9'            // control digit > 9
bgt 99f
b 11b                  // and loop

13:
cmp x4,#0              // number digit exposant = 0 -> error
beq 99f                // error
cmp x4,#2              // number digit exposant > 2 -> error
bgt 99f                // error

mov x0,#3              // valid float with exposant
b 100f
14:
cmp x3,#0
bne 15f
mov x0,#1              // valid integer
b 100f
15:
cmp x3,#1             // number of point or comma = 1 ?
blt 100f
bgt 99f               // error
mov x0,#2             // valid float
b 100f
99:
mov x0,#0             // error
100:
ldp x4,x5,[sp],16     // restaur  2 registres
ldp x2,x3,[sp],16     // restaur  2 registres
ldp x1,lr,[sp],16     // restaur  2 registres
ret

/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"

## Action!

### Using string <-> number conversion

The solution below uses conversion string to number and number to string to determine if the string is numeric.

INCLUDE "D2:REAL.ACT" ;from the Action! Tool Kit

BYTE FUNC AreEqual(CHAR ARRAY a,b)
BYTE i

IF a(0)#b(0) THEN
RETURN (0)
FI
FOR i=1 to a(0)
DO
IF a(i)#b(i) THEN
RETURN (0)
FI
OD
RETURN (1)

BYTE FUNC IsNumeric(CHAR ARRAY s)
CHAR ARRAY tmp(20)
INT i
CARD c
REAL r

i=ValI(s)
StrI(i,tmp)
IF AreEqual(s,tmp) THEN
RETURN (1)
FI

c=ValC(s)
StrC(c,tmp)
IF AreEqual(s,tmp) THEN
RETURN (1)
FI

ValR(s,r)
StrR(r,tmp)
IF AreEqual(s,tmp) THEN
RETURN (1)
FI
RETURN (0)

PROC Test(CHAR ARRAY s)
BYTE res

res=IsNumeric(s)
Print(s)
Print(" is ")
IF res=0 THEN
Print("not ")
FI
PrintE("a number.")
RETURN

PROC Main()
Put(125) PutE() ;clear the screen
Test("56233")
Test("-315")
Test("1.36")
Test("-5.126")
Test("3.7E-05")
Test("1.23BC")
Test("5.6.3")
RETURN

### Using a finite-state machine

The solution below uses a finite-state machine to determine if a string is numeric.

BYTE FUNC IsSign(CHAR c)
IF c='- OR c='+ THEN
RETURN (1)
FI
RETURN (0)

BYTE FUNC IsDigit(CHAR c)
IF c>='0 AND c<='9 THEN
RETURN (1)
FI
RETURN (0)

BYTE FUNC IsDot(CHAR c)
IF c='. THEN
RETURN (1)
FI
RETURN (0)

BYTE FUNC IsExpSymbol(CHAR c)
IF c='E OR c='e THEN
RETURN (1)
FI
RETURN (0)

BYTE FUNC IsNumeric(CHAR ARRAY s)
DEFINE S_BEGIN="0"
DEFINE S_SIGN="1"
DEFINE S_BEFORE_DOT="2"
DEFINE S_DOT="3"
DEFINE S_AFTER_DOT="4"
DEFINE S_EXP_SYMBOL="5"
DEFINE S_EXP_SIGN="6"
DEFINE S_EXP="7"

BYTE i,state
CHAR c

i=1
state=S_BEGIN
WHILE i<=s(0)
DO
c=s(i)

IF state=S_BEGIN THEN
IF IsSign(c) THEN
state=S_SIGN
ELSEIF IsDigit(c) THEN
state=S_BEFORE_DOT
ELSEIF IsDot(c) THEN
state=S_DOT
ELSE
RETURN (0)
FI
ELSEIF state=S_SIGN THEN
IF IsDigit(c) THEN
state=S_BEFORE_DOT
ELSEIF IsDot(c) THEN
state=S_DOT
ELSE
RETURN (0)
FI
ELSEIF state=S_BEFORE_DOT THEN
IF IsDigit(c) THEN
state=S_BEFORE_DOT
ELSEIF IsDot(c) THEN
state=S_DOT
ELSEIF IsExpSymbol(c) THEN
state=S_EXP_SYMBOL
ELSE
RETURN (0)
FI
ELSEIF state=S_DOT THEN
IF IsDigit(c) THEN
state=S_AFTER_DOT
ELSEIF IsExpSymbol(c) THEN
state=S_EXP_SYMBOL
ELSE
RETURN (0)
FI
ELSEIF state=S_AFTER_DOT THEN
IF IsDigit(c) THEN
state=S_AFTER_DOT
ELSEIF IsExpSymbol(c) THEN
state=S_EXP_SYMBOL
ELSE
RETURN (0)
FI
ELSEIF state=S_EXP_SYMBOL THEN
IF IsSign(c) THEN
state=S_EXP_SIGN
ELSEIF IsDigit(c) THEN
state=S_EXP
ELSE
RETURN (0)
FI
ELSEIF state=S_EXP_SIGN THEN
IF IsDigit(c) THEN
state=S_EXP
ELSE
RETURN (0)
FI
ELSEIF state=S_EXP THEN
IF IsDigit(c) THEN
state=S_EXP
ELSE
RETURN (0)
FI
ELSE
RETURN (0)
FI
i==+1
OD

IF state=S_BEGIN OR state=S_DOT OR
state=S_EXP_SIGN OR state=S_EXP_SIGN THEN
RETURN (0)
FI
RETURN (1)

PROC Test(CHAR ARRAY s)
BYTE res

res=IsNumeric(s)
Print(s)
Print(" is ")
IF res=0 THEN
Print("not ")
FI
PrintE("a number.")
RETURN

PROC Main()
Test("56233")
Test("-315")
Test("1.36")
Test("-5.126")
Test("3.7E-05")
Test("1.23BC")
Test("5.6.3")
RETURN
Output:
56233 is a number.
-315 is a number.
1.36 is a number.
-5.126 is a number.
3.7E-05 is a number.
1.23BC is not a number.
5.6.3 is not a number.


## ActionScript

public function isNumeric(num:String):Boolean
{
return !isNaN(parseInt(num));
}


The first file is the package interface containing the declaration of the Is_Numeric function.

package Numeric_Tests is
function Is_Numeric (Item : in String) return Boolean;
end Numeric_Tests;


The second file is the package body containing the implementation of the Is_Numeric function.

package body Numeric_Tests is
function Is_Numeric (Item : in String) return Boolean is
Dummy : Float;
begin
Dummy := Float'Value (Item);
return True;
exception
when others =>
return False;
end Is_Numeric;
end Numeric_Tests;


The last file shows how the Is_Numeric function can be called.

with Ada.Text_Io; use Ada.Text_Io;
with Numeric_Tests; use Numeric_Tests;

procedure Is_Numeric_Test is
S1 : String := "152";
S2 : String := "-3.1415926";
S3 : String := "Foo123";
begin
Put_Line(S1 & " results in " & Boolean'Image(Is_Numeric(S1)));
Put_Line(S2 & " results in " & Boolean'Image(Is_Numeric(S2)));
Put_Line(S3 & " results in " & Boolean'Image(Is_Numeric(S3)));
end Is_Numeric_Test;

Output:
 152 results in TRUE
-3.1415926 results in TRUE
Foo123 results in FALSE


## Aime

integer
is_numeric(text s)
{
return !trap_q(alpha, s, 0);
}

integer
main(void)
{
if (!is_numeric("8192&*")) {
o_text("Not numeric.\n");
}
if (is_numeric("8192")) {
o_text("Numeric.\n");
}

return 0;
}

## ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
PROC is numeric = (REF STRING string) BOOL: (
BOOL out := TRUE;
PROC call back false = (REF FILE f)BOOL: (out:= FALSE; TRUE);

FILE memory;
associate(memory, string);
on value error(memory, call back false);
on logical file end(memory, call back false);

UNION (INT, REAL, COMPL) numeric:=0.0;
# use a FORMAT pattern instead of a regular expression #
getf(memory, ($gl$, numeric));
out
);

test:(
STRING
s1 := "152",
s2 := "-3.1415926",
s3 := "Foo123";
print((
s1, " results in ", is numeric(s1), new line,
s2, " results in ", is numeric(s2), new line,
s3, " results in ", is numeric(s3), new line
))
)
Output:
152 results in T
-3.1415926 results in T
Foo123 results in F


## ALGOL W

begin

% determnines whether the string contains an integer, real or imaginary  %
% number. Returns true if it does, false otherwise                       %
logical procedure isNumeric( string(32) value text ) ;
begin

logical ok;
% the "number" cannot be blank                                   %
ok := ( text not = " " );
if ok then begin

% there is at least one non-blank character                  %
% must have either an integer or real/immaginary number      %
% integer: [+|-]digit-sequence                               %
% real:    [+|-][digit-sequence].digit-sequence['integer][L] %
% or:      [+|-]digit-sequence[.[digit-sequence]]'integer[L] %
% imaginary:                                                 %
%          [+|-][digit-sequence].digit-sequence['integer][L]I%
% or:      [+|-]digit-sequence[.[digit-sequence]]'integer[L]I%
% The "I" at the end of an imaginary number can appear       %
% before or after the "L" (which indicates a long number)    %
% the "I" and "L" can be in either case                      %

procedure nextChar ; charPos := charPos + 1;
logical procedure have( string(1) value ch ) ;
( charPos <= maxChar and text(charPos//1) = ch ) ;

logical procedure haveDigit ;
( charPos <= maxChar and text(charPos//1) >= "0" and text(charPos//1) <= "9" ) ;

integer charPos, maxChar;
charPos   :=  0;
maxChar   := 31;
isReal    := false;

% skip trailing spaces                                       %
while maxChar > 0 and text(maxChar//1) = " " do maxChar := maxChar - 1;
while have( " " ) do nextChar;

% skip optional sign                                         %
if have( "+" ) or have( "-" ) then nextChar;

if      haveDigit then begin
% have a digit sequence                                  %
while haveDigit do nextChar
end if_have_sign ;

if have( "." ) then begin
% real or imaginary number                               %
nextChar;
isReal    := true;
while haveDigit do nextChar
end if_have_point ;

% should have had some digits                                %

if ok and have( "'" ) then begin
% the number has an exponent                             %
isReal := true;
nextChar;
% skip optional sign                                     %
if have( "+" ) or have( "-" ) then nextChar;
% must have a digit sequence                             %
ok := haveDigit;
while haveDigit do nextChar;
end if_ok_and_have_exponent ;

% if it is a real number, there could be L/I suffixes        %
if ok and isReal then begin
integer LCount, ICount;
LCount := 0;
ICount := 0;
while have( "L" ) or have( "l" ) or have( "I" ) or have( "i" ) do begin
if have( "L" ) or have( "l" )
then LCount := LCount + 1
else ICount := ICount + 1;
nextChar
end while_have_L_or_I ;
% there can be at most one L and at most 1 I             %
ok := ( LCount < 2 and ICount < 2 )
end if_ok_and_isReal ;

% must now be at the end if the number                       %
ok := ok and charPos >= maxChar

end if_ok ;

ok
end isNumeric ;

% test the isNumeric procedure                                           %
procedure testIsNumeric( string(32) value n
; logical    value expectedResult
) ;
begin
logical actualResult;
actualResult := isNumeric( n );
write( s_w := 0
, """", n, """ is "
, if actualResult then "" else "not "
, "numeric "
, if actualResult = expectedResult then "" else " NOT "
, "as expected"
)
end testIsNumeric ;

testIsNumeric(          "", false );
testIsNumeric(         "b", false );
testIsNumeric(         ".", false );
testIsNumeric(       ".'3", false );
testIsNumeric(       "3.'", false );
testIsNumeric(    "0.0z44", false );
testIsNumeric(      "-1IL", false );
testIsNumeric( "4.5'23ILL", false );

write( "---------" );

testIsNumeric(        "-1", true  );
testIsNumeric(    " +.345", true  );
testIsNumeric(   "4.5'23I", true  );
testIsNumeric(    "-5'+3i", true  );
testIsNumeric(    "-5'-3l", true  );
testIsNumeric(  " -.345LI", true  );

end.
Output:
"                                " is not numeric as expected
"b                               " is not numeric as expected
".                               " is not numeric as expected
".'3                             " is not numeric as expected
"3.'                             " is not numeric as expected
"0.0z44                          " is not numeric as expected
"-1IL                            " is not numeric as expected
"4.5'23ILL                       " is not numeric as expected
---------
"-1                              " is numeric as expected
" +.345                          " is numeric as expected
"4.5'23I                         " is numeric as expected
"-5'+3i                          " is numeric as expected
"-5'-3l                          " is numeric as expected
" -.345LI                        " is numeric as expected


## Apex

The isNumeric() method is part of the Apex String Class. Note that it will return false if applied to a decimal, because the '.' character is not a Unicode digit.

String numericString = '123456';
String partlyNumericString = '123DMS';
String decimalString = '123.456';

System.debug(numericString.isNumeric()); // this will be true
System.debug(partlyNumericString.isNumeric()); // this will be false
System.debug(decimalString.isNumeric()); // this will be false
System.debug(decimalString.remove('.').isNumeric()); // this will be true

## APL

Works with: Dyalog APL
      ⊃⎕VFI{w←⍵⋄((w='-')/w)←'¯'⋄w}'152 -3.1415926 Foo123'

1 1 0

       ⊃⎕VFI '¯' @ ('-'∘=)   '152 -3.1415926 Foo123'     ⍝ Fast:  replacement of - with APL high-minus required for ⎕VFI
1 1 0
⊃⎕VFI '-' ⎕R '¯'    ⊣ '152 -3.1415926 Foo123'     ⍝ Simple: (ditto)
1 1 0

Works with: GNU APL
      {∧/⍵∊(⊃,¨'0123456789¯.+')}¨'152' '¯3.1415926' 'Foo123'
1 1 0


## AppleScript

-- isNumString :: String -> Bool
on isNumString(s)
try
if class of s is string then
set c to class of (s as number)
c is real or c is integer
else
false
end if
on error
false
end try
end isNumString

-- TEST
on run

map(isNumString, {3, 3.0, 3.5, "3.5", "3E8", "-3.5", "30", "three", three, four})

--> {false, false, false, true, true, true, true, false, false, false}

end run

-- three :: () -> Int
script three
3
end script

-- four :: () -> Int
on four()
4
end four

-- GENERIC FUNCTIONS FOR TEST

-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to lambda(item i of xs, i, xs)
end repeat
return lst
end tell
end map

-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
if class of f is script then
f
else
script
property lambda : f
end script
end if
end mReturn

Output:
{false, false, false, true, true, true, true, false, false, false}


The classic way's slightly simpler, since the coercion result must be a real or an integer if the coercion itself didn't error.

on isNumString(s)
if (s's class is not text) then return false
try
s as number
return true
on error
return false
end try
end isNumString


## ARM Assembly

Works with: as version Raspberry Pi
/* ARM assembly Raspberry PI  */
/*  program strNumber.s   */

/* Constantes    */
.equ STDIN,  0                           @ Linux input console
.equ STDOUT, 1                           @ Linux output console
.equ EXIT,   1                           @ Linux syscall
.equ READ,   3                           @ Linux syscall
.equ WRITE,  4                           @ Linux syscall

.equ BUFFERSIZE,          100

/* Initialized data */
.data
szMessNum: .asciz "Enter number : \n"

szMessError:            .asciz "String is not a number !!!\n"
szMessInteger:          .asciz "String is a integer.\n"
szMessFloat:            .asciz "String is a float.\n"
szMessFloatExp:         .asciz "String is a float with exposant.\n"
szCarriageReturn:       .asciz "\n"

/* UnInitialized data */
.bss
sBuffer:              .skip BUFFERSIZE

/*  code section */
.text
.global main
main:

loop:
bl affichageMess
mov r0,#STDIN                               @ Linux input console
mov r2,#BUFFERSIZE                          @ buffer size
swi 0                                       @ call system
mov r2,#0                                   @ end of string
sub r0,#1                                   @ replace character 0xA
strb r2,[r1,r0]                             @ store byte at the end of input string (r0 contains number of characters)
bl controlNumber                            @ call routine
cmp r0,#0
bne 1f
ldr r0,iAdrszMessError                      @ not a number
bl affichageMess
b 5f
1:
cmp r0,#1
bne 2f
bl affichageMess
b 5f
2:
cmp r0,#2
bne 3f
bl affichageMess
b 5f
3:
cmp r0,#3
bne 5f
ldr r0,iAdrszMessFloatExp                   @ float with exposant
bl affichageMess
5:
b loop

100:                                            @ standard end of the program
mov r0, #0                                  @ return code
mov r7, #EXIT                               @ request to exit program
svc 0                                       @ perform system call
/******************************************************************/
/*     control if string is number                          */
/******************************************************************/
/* r0 contains the address of the string */
/* r0 return 0 if not a number       */
/* r0 return 1 if integer   eq 12345 or -12345      */
/* r0 return 2 if float     eq 123.45 or 123,45  or -123,45     */
/* r0 return 3 if float with exposant  eq 123.45E30 or -123,45E-30        */
controlNumber:
push {r1-r4,lr}                       @ save  registers
mov r1,#0
mov r3,#0          @ point counter
1:
ldrb r2,[r0,r1]
cmp r2,#0
beq 5f
cmp r2,#' '
beq   1b
cmp r2,#'-'                    @ negative ?
beq 2f
cmp r2,#'+'                    @ positive ?
2:
ldrb r2,[r0,r1]                @ control space
cmp r2,#0                      @ end ?
beq 5f
cmp r2,#' '
beq 2b
3:
ldrb r2,[r0,r1]
cmp r2,#0                 @ end ?
beq 10f
cmp r2,#'E'               @ exposant ?
beq 6f
cmp r2,#'e'               @ exposant ?
beq 6f
cmp r2,#'.'               @ point ?
addeq r3,#1               @ yes increment counter
beq 3b
cmp r2,#','               @ comma ?
addeq r3,#1               @ yes increment counter
beq 3b
cmp r2,#'0'               @ control digit < 0
blt 5f
cmp r2,#'9'               @ control digit > 0
bgt 5f
add r1,#1                 @ no error loop digit
b 3b
5:                            @ error detected
mov r0,#0
b 100f
6:    @ float with exposant
ldrb r2,[r0,r1]
cmp r2,#0             @ end ?
moveq r0,#0           @ error
beq 100f
cmp r2,#'-'           @ negative exposant ?
mov r4,#0             @ nombre de chiffres
7:
ldrb r2,[r0,r1]
cmp r2,#0             @ end ?
beq 9f
cmp r2,#'0'           @ control digit < 0
blt 8f
cmp r2,#'9'           @ control digit > 0
bgt 8f
b 7b
8:
mov r0,#0
b 100f
9:
cmp r4,#0             @ number digit exposant = 0 -> error
moveq r0,#0           @ erreur
beq 100f
cmp r4,#2             @ number digit exposant > 2 -> error
movgt r0,#0           @ error
bgt 100f
mov r0,#3             @ valid float with exposant
b 100f
10:
cmp r3,#0
moveq r0,#1           @ valid integer
beq 100f
cmp r3,#1             @ number of point or comma = 1 ?
moveq r0,#2           @ valid float
movgt r0,#0           @ error
100:
pop {r1-r4,lr}                         @ restaur des  2 registres
bx lr                                        @ return
/******************************************************************/
/*     display text with size calculation                         */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {r0,r1,r2,r7,lr}                       @ save  registers
mov r2,#0                                   @ counter length */
1:                                              @ loop length calculation
ldrb r1,[r0,r2]                             @ read octet start position + index
cmp r1,#0                                   @ if 0 its over
bne 1b                                      @ and loop
@ so here r2 contains the length of the message
mov r1,r0                                   @ address message in r1
mov r0,#STDOUT                              @ code to write to the standard output Linux
mov r7, #WRITE                              @ code call system "write"
svc #0                                      @ call system
pop {r0,r1,r2,r7,lr}                        @ restaur registers
bx lr                                       @ return

## Arturo

print numeric? "hello world"
print numeric? "1234"
print numeric? "1234 hello world"
print numeric? "12.34"
print numeric? "!#@$" print numeric? "-1.23"  Output: false true false true false true ## AutoHotkey AutoHotkey has no explicitly defined variable types. A variable containing only digits (with an optional decimal point) is automatically interpreted as a number when a math operation or comparison requires it. list = 0 .14 -5.2 ten 0xf Loop, Parse, list, %A_Space% MsgBox,% IsNumeric(A_LoopField) Return IsNumeric(x) { If x is number Return, 1 Else Return, 0 } ;Output: 1 1 1 0 1  ## AWK The following function uses the fact that non-numeric strings in AWK are treated as having the value 0 when used in arithmetics, but not in comparison: $ awk 'function isnum(x){return(x==x+0)} BEGIN{print isnum("hello"),isnum("-42")}'

Output:
0 1


## BaCon

INPUT "Your string: ", s$IF REGEX(s$, "^[-+]?[0-9]*\\.?[0-9]+([eE][-+]?[0-9]+)?$") THEN PRINT "This is a number" ELSE PRINT "Not a number" ENDIF Output: user@host$ ./isnumber
This is a number
user@host $./isnumber Your string: 12E3 This is a number user@host$ ./isnumber
Not a number
user@host $./isnumber Your string: Hello Not a number  ## BASIC 10 INPUT "Enter a string";S$:GOSUB 1000
20 IF R THEN PRINT "Is num" ELSE PRINT"Not num"
99 END
1000 T1=VAL(S$):T1$=STR$(T1) 1010 R=T1$=S$OR T1$=" "+S$1099 RETURN  ### BASIC256 #La función isNumeric() es nativa de BASIC256. #Devuelve 1 (verdadero) si la expresión es un entero, #un número de punto flotante o una cadena que se puede #convertir directamente en un número. #De lo contrario, devuelve 0 (falso). #Las siguientes cadenas numéricas son válidas: #“123”, “-345”, “234.234324”, “-34234.123”, “-2.567e7” y “6.7888E-8”. s = "1234.056789" print s, " => "; isNumeric(s) s = "-2.567e7" print s, " => "; isNumeric(s) s = "Dog" print s, " => "; isNumeric(s) s = "Bad125" print s, " => "; isNumeric(s) s = "-0177" print s, " => "; isNumeric(s) s = "0b1110" #binario print s, " => "; isNumeric(s) s = "0o177" #octal print s, " => "; isNumeric(s) s = "0xff" #hexadecimal print s, " => "; isNumeric(s) end Output: 1234.056789 => 1 -2.567e7 => 1 Dog => 0 Bad125 => 0 -0177 => 1 0b1110 => 1 0o177 => 1 0xff => 0  ### Commodore BASIC 5 print chr$(147);chr$(14) 10 input "Enter a string";s$:gosub 1000:print
20 if r then print "You entered a number.":goto 99
30 print "That is not a number."
99 end
1000 t1=val(s$):t1$=str$(t1) 1010 r=t1$=s$or t1$=" "+s$1099 return Output: Enter a string? 15893 You entered a number. ready. run Enter a string? Llamas That is not a number. ready. █ ### QB64 Input "Enter a text or a number: ", v$ 'The "$" establishes that this is a string variable. So whatever entered will be stored as 'a string. If v$ = Str$(Val(v$)) Then             'Str$() converts numeric values to their string counter parts and Val() does the opposite, 'converting strings to their numerical values. By converting the value of whatever is stored 'in v$ to a number and then back to a string it will have either stayed completely the same,
'in which case it is a numeric value (including exponent and hex and oct based numbers) or
'what is returned by the nested Str$() and Val$() functions will be different, in which case
'one, the other, or both returned an error or a truncation of the original string which began
'with numeric characters but was not entirely a number, such as "99, rue de Rivoli".
Else
Print "You did not enter a number."
End If
Sleep
System
Output:
Enter a text or a number: 12345
You entered a number.

Enter a text or a number: Four
You did not enter a number.

Enter a text or a number: 99, rue de Rivoli
You did not enter a number.

Enter a text or a number: 9E4
You entered a number.

NB: While "99, rue de Rivoli" contains a number it is not a number entirely. The Val(v$) in this case would have stopped after it converted the "99" portion of the input, which when converted back to a string and compared to the original input would not result in an equality. 9E4 the program reads as an exponential value. ## Batch File set /a a=%arg%+0 >nul if %a% == 0 ( if not "%arg%"=="0" ( echo Non Numeric. ) else ( echo Numeric. ) ) else ( echo Numeric. )  ## BBC BASIC  REPEAT READ N$
IF FN_isanumber(N$) THEN PRINT "'" N$ "' is a number"
ELSE
PRINT "'" N$"' is NOT a number" ENDIF UNTIL N$ = "end"
END

DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0"
DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end"

DEF FN_isanumber(A$) ON ERROR LOCAL = FALSE IF EVAL("(" + A$ + ")") <> VAL(A$) THEN = FALSE IF VAL(A$) <> 0 THEN = TRUE
IF LEFT$(A$,1) = "0" THEN = TRUE
= FALSE

Output:
'PI' is NOT a number
'0123' is a number
'-0123' is a number
'12.30' is a number
'-12.30' is a number
'123!' is NOT a number
'0' is a number
'0.0' is a number
'.123' is a number
'-.123' is a number
'12E3' is a number
'12E-3' is a number
'12+3' is NOT a number
'end' is NOT a number

## Befunge

 ~:0\#v_:"+"-!#v_:"-"-!#v_::"E"-\"e"-*#v_                               v
v       _v#     <        <             0<
>~:0\#v_>::"0"-0\\"9"-0+!#v_:"."-!#v_::"E"-\"e"-*!#v_                 v
^                           $< > >$               v
>~:0\#v_>::"0"-0\\"9"-0+!#v_:"."-!#v_::"E"-\"e"-*!#v_>                v>
^                           $< >$~:0\#v_:"+"-#v_v
v      $_v# < < :#< >~:0\#v_>::"0"-0\\"9"-0+!#v_:"."-!#v_::"E"-\"e"-*!v 0 > v ^$<        v                 <    << ^_^#-"-"<
> "ciremuN">:#,_@             >>#$_"ciremun toN">:#,_@^ <  Although only integer inputs are strictly allowed in Befunge, the code tries to adhere to the floating point conventions in other languages when recognising valid numbers. Output: 'PI' Not numeric '0123' Numeric '-0123' Numeric '12.30' Numeric '-12.30' Numeric '123!' Not numeric '0' Numeric '0.0' Numeric '.123' Numeric '-.123' Numeric '12E3' Numeric '12E-3' Numeric '12+3' Not numeric 'end' Not numeric '12..34' Not numeric '12e3.4' Not numeric '192.168.0.1' Not numeric  ## Bracmat To check whether a string is a number, a fraction or an integer, use the patterns #, / and ~/# ("not a fraction and yet a number"). In the pattern matching examples below (which can be typed in at the Bracmat prompt) F denotes 'failure' and S denotes 'success'. 43257349578692:/ F 260780243875083/35587980:/ S 247/30:~/# F 80000000000:~/# S Bracmat doesn't do floating point computations (historical reason: the Acorn Risc Machine a.k.a. ARM processor in the Archimedes computer did not have an FPU), but the pattern ~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#) recognises string representations of floating point numbers. @("1.000-4E-10":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) F @("1.0004E-54328":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("-464641.0004E-54328":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("1/2.0004E-10":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) F @("1357E-10":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("1357e0":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("13579":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("1.246":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("0.0":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S @("0.0000":~/# (|"." (|? 0|) (|~/#:>0)) (|(E|e) ~/#)) S To do computations with such "floating point strings" you would have to convert such strings to fractional representations first. (float2fraction= integerPart decimalPart d1 dn exp sign . @( !arg : ~/#?integerPart ( &0:?decimalPart:?d1:?dn | "." [?d1 (|? 0|) ( &0:?decimalPart | ~/#?decimalPart:>0 ) [?dn ) ( &0:?exp | (E|e) ~/#?exp ) ) & ( !integerPart*(-1:?sign):>0:?integerPart | 1:?sign ) & !sign*(!integerPart+!decimalPart*10^(!d1+-1*!dn))*10^!exp ); ( out$float2fraction$"1.2" & out$float2fraction$"1.02" & out$float2fraction$"1.01" & out$float2fraction$"10.01" & out$float2fraction$"10.01e10" & out$float2fraction$"10.01e1" & out$float2fraction$"10.01e2" & out$float2fraction$"10.01e-2" & out$float2fraction$"-10.01e-2" & out$float2fraction$"-10e-2" & out$float2fraction$"0.000" ); Output: 6/5 51/50 101/100 1001/100 100100000000 1001/10 1001 1001/10000 -1001/10000 -1/10 0 ## Burlesque ps^^-]to{"Int""Double"}\/~[\/L[1==?* Assumes string is not empty. ## C Returns true (non-zero) if character-string parameter represents a signed or unsigned floating-point number. Otherwise returns false (zero). #include <ctype.h> #include <stdlib.h> int isNumeric (const char * s) { if (s == NULL || *s == '\0' || isspace(*s)) return 0; char * p; strtod (s, &p); return *p == '\0'; }  ## C# Framework: .NET 2.0+ public static bool IsNumeric(string s) { double Result; return double.TryParse(s, out Result); // TryParse routines were added in Framework version 2.0. } string value = "123"; if (IsNumeric(value)) { // do something }  Framework: .NET 1.0+ public static bool IsNumeric(string s) { try { Double.Parse(s); return true; } catch { return false; } }  ## C++ Using stringstream: #include <sstream> // for istringstream using namespace std; bool isNumeric( const char* pszInput, int nNumberBase ) { istringstream iss( pszInput ); if ( nNumberBase == 10 ) { double dTestSink; iss >> dTestSink; } else if ( nNumberBase == 8 || nNumberBase == 16 ) { int nTestSink; iss >> ( ( nNumberBase == 8 ) ? oct : hex ) >> nTestSink; } else return false; // was any input successfully consumed/converted? if ( ! iss ) return false; // was all the input successfully consumed/converted? return ( iss.rdbuf()->in_avail() == 0 ); }  Using find: bool isNumeric( const char* pszInput, int nNumberBase ) { string base = "0123456789ABCDEF"; string input = pszInput; return (input.find_first_not_of(base.substr(0, nNumberBase)) == string::npos); }  Using all_of (requires C++11) bool isNumeric(const std::string& input) { return std::all_of(input.begin(), input.end(), ::isdigit); }  ## CFScript ColdFusion Script (CfScript) isNumeric(42)  ## Clojure (defn numeric? [s] (if-let [s (seq s)] (let [s (if (= (first s) \-) (next s) s) s (drop-while #(Character/isDigit %) s) s (if (= (first s) \.) (next s) s) s (drop-while #(Character/isDigit %) s)] (empty? s))))  This works with any sequence of characters, not just Strings, e.g.: (numeric? [\1 \2 \3]) ;; yields logical true  Clojure has a fairly rich set of numeric literals, including Ratios, BigInts and BigDecimals. The Clojure reader will attempt to read any form starting with a digit (optionally preceded by a '+' or '-') as a number. So the following checks to see if such a read is successful: (require '[clojure.edn :as edn]) (import [java.io PushbackReader StringReader]) (defn number-string? [s] (boolean (when (and (string? s) (re-matches #"^[+-]?\d.*" s)) (let [reader (PushbackReader. (StringReader. s)) num (try (edn/read reader) (catch Exception _ nil))] (when num ; Check that the string has nothing after the number (= -1 (.read reader)))))))  user=> (number-string? "2r101010") true user=> (number-string? "22/7") true  ## COBOL ### Intrinsic Functions COBOL has the intrinsic functions TEST-NUMVAL and TEST-NUMVAL-C to check if a string is numeric (TEST-NUMVAL-C is used to check if it is also a monetary string). Implementations supporting the 20XX draft standard can also use TEST-NUMVAL-F for floating-point numbers. They return 0 if the string is valid, or the position of the first incorrect character.  program-id. is-numeric. procedure division. display function test-numval-f("abc") end-display display function test-numval-f("-123.01E+3") end-display if function test-numval-f("+123.123") equal zero then display "is numeric" end-display else display "failed numval-f test" end-display end-if goback.  ### Implementation Works with: OpenCOBOL  IDENTIFICATION DIVISION. PROGRAM-ID. Is-Numeric. DATA DIVISION. WORKING-STORAGE SECTION. 01 Numeric-Chars PIC X(10) VALUE "0123456789". 01 Success CONSTANT 0. 01 Failure CONSTANT 128. LOCAL-STORAGE SECTION. 01 I PIC 99. 01 Num-Decimal-Points PIC 99. 01 Num-Valid-Chars PIC 99. LINKAGE SECTION. 01 Str PIC X(30). PROCEDURE DIVISION USING Str. IF Str = SPACES MOVE Failure TO Return-Code GOBACK END-IF MOVE FUNCTION TRIM(Str) TO Str INSPECT Str TALLYING Num-Decimal-Points FOR ALL "." IF Num-Decimal-Points > 1 MOVE Failure TO Return-Code GOBACK ELSE ADD Num-Decimal-Points TO Num-Valid-Chars END-IF IF Str (1:1) = "-" OR "+" ADD 1 TO Num-Valid-Chars END-IF PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10 INSPECT Str TALLYING Num-Valid-Chars FOR ALL Numeric-Chars (I:1) BEFORE SPACE END-PERFORM INSPECT Str TALLYING Num-Valid-Chars FOR TRAILING SPACES IF Num-Valid-Chars = FUNCTION LENGTH(Str) MOVE Success TO Return-Code ELSE MOVE Failure TO Return-Code END-IF GOBACK .  ## CoffeeScript The isFinite function is built into JavaScript, so we don't need to create our own function in CoffeeScript. console.log (isFinite(s) for s in [5, "5", "-5", "5", "5e5", 0]) # all true console.log (isFinite(s) for s in [NaN, "fred", "###"]) # all false  ## ColdFusion Adobe's ColdFusion <cfset TestValue=34> TestValue: <cfoutput>#TestValue#</cfoutput><br> <cfif isNumeric(TestValue)> is Numeric. <cfelse> is NOT Numeric. </cfif> <cfset TestValue="NAS"> TestValue: <cfoutput>#TestValue#</cfoutput><br> <cfif isNumeric(TestValue)> is Numeric. <cfelse> is NOT Numeric. </cfif>  ### Alternative solution <cfoutput>#isNumeric(42)#</cfoutput>  ## Common Lisp If the input may be relied upon to not be especially malicious, then it may be read and the result checked for being a number. (defun numeric-string-p (string) (let ((*read-eval* nil)) (ignore-errors (numberp (read-from-string string)))))  ignore-errors here handles returning nil in case the input is invalid rather than simply non-numeric. However, read[-from-string] has the side effect of interning any symbols encountered, and can have memory allocation larger than the input size (due to read syntax such as #*, which takes a length). The parse-number library provides a numbers-only equivalent of read. (defun numeric-string-p (string) (ignore-errors (parse-number:parse-number string))) ; parse failed, return false (nil)  ## D ### Standard Version Using the standard Phobos function (currently binary and hex literals are not recognized): import std.stdio, std.string, std.array; void main() { foreach (const s; ["12", " 12\t", "hello12", "-12", "02", "0-12", "+12", "1.5", "1,000", "1_000", "0x10", "0b10101111_11110000_11110000_00110011", "-0b10101", "0x10.5"]) writefln(isNumeric("%s"): %s, s, s.strip().isNumeric(true)); }  Output: isNumeric("12"): true isNumeric(" 12 "): true isNumeric("hello12"): false isNumeric("-12"): true isNumeric("02"): true isNumeric("0-12"): false isNumeric("+12"): true isNumeric("1.5"): true isNumeric("1,000"): true isNumeric("1_000"): true isNumeric("0x10"): false isNumeric("0b10101111_11110000_11110000_00110011"): false isNumeric("-0b10101"): false isNumeric("0x10.5"): false ### An Implementation import std.stdio, std.string, std.conv, std.array, std.exception; bool isNumeric(in string s) pure { immutable s2 = s.strip.toLower.replace("_", "").replace(",", ""); try { s2.to!real; } catch (ConvException e) { if (s2.startsWith("0x")) return !s2[2 ..$].to!ulong(16)
.collectException!ConvException;
else if (s2.startsWith("0b"))
return !s2[2 .. $].to!ulong(2) .collectException!ConvException; else return false; } return true; } void main() { foreach (immutable s; ["12", " 12\t", "hello12", "-12", "02", "0-12", "+12", "1.5", "1,000", "1_000", "0x10", "0b10101111_11110000_11110000_00110011", "-0b10101", "0x10.5"]) writefln(isNumeric("%s"): %s, s, s.isNumeric); }  Output: isNumeric("12"): true isNumeric(" 12 "): true isNumeric("hello12"): false isNumeric("-12"): true isNumeric("02"): true isNumeric("0-12"): false isNumeric("+12"): true isNumeric("1.5"): true isNumeric("1,000"): true isNumeric("1_000"): true isNumeric("0x10"): true isNumeric("0b10101111_11110000_11110000_00110011"): true isNumeric("-0b10101"): false isNumeric("0x10.5"): false ## Delphi This simple function is a wrapper around a built-in Delphi function function IsNumericString(const inStr: string): Boolean; var i: extended; begin Result := TryStrToFloat(inStr,i); end;  This console application tests the function: program isNumeric; {$APPTYPE CONSOLE}

uses
Classes,
SysUtils;

function IsNumericString(const inStr: string): Boolean;
var
i: extended;
begin
Result := TryStrToFloat(inStr,i);
end;

{ Test function }
var
s: string;
c: Integer;

const
MAX_TRIES = 10;
sPROMPT   = 'Enter a string (or type "quit" to exit):';
sIS       = ' is numeric';
sISNOT    = ' is NOT numeric';

begin
c := 0;
s := '';
repeat
Inc(c);
Writeln(sPROMPT);
if (s <> '') then
begin
if IsNumericString(s) then
begin
Writeln(s+sIS);
end
else
begin
Writeln(s+sISNOT);
end;
Writeln('');
end;
until
(c >= MAX_TRIES) or (LowerCase(s) = 'quit');

end.

Output:
Example summarised
123 is numeric
-123.456 is numeric
-123.-456 is NOT numeric
.345 is numeric
m1k3 is NOT numeric


## Dyalect

func String.IsNumeric() {
try {
parse(this) is Integer or Float
} catch _ {
false
}
}

var str = "1234567"
print(str.IsNumeric())

## Déjà Vu

is-numeric s:
true
try:
drop to-num s
catch value-error:
not

for v in [ "1" "0" "3.14" "hello" "12e3" "12ef" "-3" ]:
!.( v is-numeric v )
Output:
"-3" true
"12ef" false
"12e3" true
"hello" false
"3.14" true
"0" true
"1" true

## E

def isNumeric(specimen :String) {
try {
<import:java.lang.makeDouble>.valueOf(specimen)
return true
} catch _ {
return false
}
}

## EasyLang

proc is_numeric a$. r . h = number a$
r = 1 - error
# because every variable must be used
h = h
.
for s$in [ "abc" "21a" "1234" "-13" "7.65" ] call is_numeric s$ r
if r = 1
print s$& " is numeric" else print s$ & " is not numeric"
.
.


## EchoLisp

The conversion function string->number returns #f - false - in the string is not a number, else returns a number, which is #t - true - as far as logical operations are concerned

(string->number "albert")
→ #f
(string->number -666)
→ -666
(if (string->number 666) 'YES 'NO)
→ YES


## Elixir

defmodule RC do
def is_numeric(str) do
case Float.parse(str) do
{_num, ""} -> true
_          -> false
end
end
end

["123", "-12.3", "123.", ".05", "-12e5", "+123", " 123", "abc", "123a", "12.3e", "1 2"] |> Enum.filter(&RC.is_numeric/1)

Output:
["123", "-12.3", "-12e5", "+123"]


## EMal

fun isNumeric = logic by text value
try
^|So funny:
|a) we check if it's castable to a real
|b) we obtain the real 0.0
|c) conversion from real to int to get 0
|d) int can be converted to logical to get ⊥
|e) we can negate the result
|^
return not when(value.contains("."), logic!int!(real!value * 0), logic!(int!value * 0))
remedy
return false
end
end
fun main = int by List args
if args.length == 1
writeLine(isNumeric(args[0]))
else
writeLine("value".padEnd(8, " ") + " " + "numeric")
for each text value in text["0o755", "thursday", "3.14", "0b1010", "-100", "0xff"]
writeLine(value.padEnd(8, " ") + " " + isNumeric(value))
end
end
return 0
end
exit main(Runtime.args)
Output:
value    numeric
0o755    ⊤
thursday ⊥
3.14     ⊤
0b1010   ⊤
-100     ⊤
0xff     ⊤


## Erlang

Erlang doesn't come with a way to say if a string represents a numeric value or not, but does come with the built-in function is_number/1, which will return true if the argument passed is either an integer or a float. Erlang also has two functions to transform a string to either a floating number or an integer, which will be used in conjunction with is_number/1.

is_numeric(L) ->
Float = (catch erlang:list_to_float(L)),
Int = (catch erlang:list_to_integer(L)),
is_number(Float) orelse is_number(Int).


## ERRE

Short form using predeclared ERRE functions VAL and STR$. PROGRAM NUMERIC PROCEDURE IS_NUMERIC(S$->ANS%)
LOCAL T1,T1$T1=VAL(S$)
T1$=STR$(T1)
ANS%=(T1$=S$) OR T1$=" "+S$
END PROCEDURE

BEGIN
PRINT(CHR$(12);) INPUT("Enter a string",S$)
IS_NUMERIC(S$->ANS%) IF ANS% THEN PRINT("is num") ELSE PRINT("not num") END PROGRAM Output: Enter a string? 12.30 is num  ## Euphoria include get.e function is_numeric(sequence s) sequence val val = value(s) return val[1]=GET_SUCCESS and atom(val[2]) end function ## F# let is_numeric a = fst (System.Double.TryParse a)  ## Factor : numeric? ( string -- ? ) string>number >boolean ;  ## Fantom The 'fromStr' methods return a parsed number or given an error. The 'false' tells each method to return null if the string does not parse as a number of given type, otherwise, the 'fromStr' method throws an exception. class Main { // function to see if str contains a number of any of built-in types static Bool readNum (Str str) { int := Int.fromStr (str, 10, false) // use base 10 if (int != null) return true float := Float.fromStr (str, false) if (float != null) return true decimal := Decimal.fromStr (str, false) if (decimal != null) return true return false } public static Void main () { echo ("For '2': " + readNum ("2")) echo ("For '-2': " + readNum ("-2")) echo ("For '2.5': " + readNum ("2.5")) echo ("For '2a5': " + readNum ("2a5")) echo ("For '-2.1e5': " + readNum ("-2.1e5")) } } Output: For '2': true For '-2': true For '2.5': true For '2a5': false For '-2.1e5': true  ## Forth Works with: gforth version 0.6.2 : is-numeric ( addr len -- ) 2dup snumber? ?dup if \ not standard, but >number is more cumbersome to use 0< if -rot type ." as integer = " . else 2swap type ." as double = " <# #s #> type then else 2dup >float if type ." as float = " f. else type ." isn't numeric in base " base @ dec. then then ; s" 1234" is-numeric \ 1234 as integer = 1234 s" 1234." is-numeric \ 1234. as double = 1234 s" 1234e" is-numeric \ 1234e as float = 1234. s"$1234" is-numeric    \ $1234 as integer = 4660 ( hex literal ) s" %1010" is-numeric \ %1010 as integer = 10 ( binary literal ) s" beef" is-numeric \ beef isn't numeric in base 10 hex s" beef" is-numeric \ beef as integer = BEEF s" &1234" is-numeric \ &1234 as integer = 4D2 ( decimal literal )  ## Fortran FUNCTION is_numeric(string) IMPLICIT NONE CHARACTER(len=*), INTENT(IN) :: string LOGICAL :: is_numeric REAL :: x INTEGER :: e READ(string,*,IOSTAT=e) x is_numeric = e == 0 END FUNCTION is_numeric  ## Free Pascal function isNumeric(const potentialNumeric: string): boolean; var potentialInteger: integer; potentialReal: real; integerError: integer; realError: integer; begin integerError := 0; realError := 0; // system.val attempts to convert numerical value representations. // It accepts all notations as they are accepted by the language, // as well as the '0x' (or '0X') prefix for hexadecimal values. val(potentialNumeric, potentialInteger, integerError); val(potentialNumeric, potentialReal, realError); isNumeric := (integerError = 0) or (realError = 0); end;  ## FreeBASIC FreeBASIC has a built-in Val() function which converts numeric strings to doubles. However, it is not ideal for the present task since it will try to convert as much of the string as it can (so "123xyz" would convert to 123) and return 0 if a conversion on this basis is not possible (i.e. "xyz" would return 0). I've therefore written a custom function which recognizes signed numbers in bases from 2 to 16 (but only integral numbers for bases other than 10). For base 10, it will treat "123." or ".123" as numbers but not ".". It doesn't recognize scientific notation but does recognize the integral prefixes &H, &O and &B if bases 16, 8 or 2 respectively are specified. ' FB 1.05.0 Win64 Dim Shared symbols(0 To 15) As UByte For i As Integer = 48 to 57 symbols(i - 48) = i Next For i As Integer = 97 to 102 symbols(i - 87) = i Next Const plus As UByte = 43 Const minus As Ubyte = 45 Const dot As UByte = 46 Function isNumeric(s As Const String, base_ As Integer = 10) As Boolean If s = "" OrElse s = "." OrElse s = "+" OrElse s = "-" Then Return False Err = 0 If base_ < 2 OrElse base_ > 16 Then Err = 1000 Return False End If Dim t As String = LCase(s) If (t[0] = plus) OrElse (t[0] = minus) Then t = Mid(t, 2) End If If Left(t, 2) = "&h" Then If base_ <> 16 Then Return False t = Mid(t, 3) End if If Left(t, 2) = "&o" Then If base_ <> 8 Then Return False t = Mid(t, 3) End if If Left(t, 2) = "&b" Then If base_ <> 2 Then Return False t = Mid(t, 3) End if If Len(t) = 0 Then Return False Dim As Boolean isValid, hasDot = false For i As Integer = 0 To Len(t) - 1 isValid = False For j As Integer = 0 To base_ - 1 If t[i] = symbols(j) Then isValid = True Exit For End If If t[i] = dot Then If CInt(Not hasDot) AndAlso (base_ = 10) Then hasDot = True IsValid = True Exit For End If Return False ' either more than one dot or not base 10 End If Next j If Not isValid Then Return False Next i Return True End Function Dim s As String s = "1234.056789" Print s, " (base 10) => "; isNumeric(s) s = "1234.56" Print s, " (base 7) => "; isNumeric(s, 7) s = "021101" Print s, " (base 2) => "; isNumeric(s, 2) s = "Dog" Print s, " (base 16) => "; isNumeric(s, 16) s = "Bad125" Print s, " (base 16) => "; isNumeric(s, 16) s = "-0177" Print s, " (base 8) => "; isNumeric(s, 8) s = "+123abcd.ef" Print s, " (base 16) => "; isNumeric(s, 8) s = "54321" Print s, " (base 6) => "; isNumeric(s, 6) s = "123xyz" Print s, " (base 10) => "; isNumeric(s) s = "xyz" Print s, " (base 10) => "; isNumeric(s) Print Print "Press any key to quit" Sleep  Output: 1234.056789 (base 10) => true 1234.56 (base 7) => false 021101 (base 2) => false Dog (base 16) => false Bad125 (base 16) => true -0177 (base 8) => true +123abcd.ef (base 16) => false 54321 (base 6) => true 123xyz (base 10) => false xyz (base 10) => false  ## FutureBasic include "NSLog.incl" local fn StringIsNumeric( string as CFStringRef ) as BOOL BOOL flag = NO ScannerRef scanner = fn ScannerWithString( string ) if ( fn ScannerScanFloat( scanner, NULL ) ) flag = fn ScannerIsAtEnd( scanner ) end if end fn = flag NSLog(@"%d",fn StringIsNumeric( @"1.23" )) NSLog(@"%d",fn StringIsNumeric( @"-123.4e5" )) NSLog(@"%d",fn StringIsNumeric( @"alpha" )) HandleEvents Output: 1 1 0  ## Gambas Public Sub Form_Open() Dim sAnswer, sString As String sString = Trim(InputBox("Enter as string", "String or Numeric")) If IsNumber(sString) Then sAnswer = "'" & sString & "' is numeric" Else sAnswer = "'" & sString & "' is a string" Print sAnswer End  Output: 'Charlie' is a string '-00.256666' is numeric  ## Go This uses a library function to meet the task's requirements: package main import ( "fmt" "strconv" ) func isNumeric(s string) bool { _, err := strconv.ParseFloat(s, 64) return err == nil } func main() { fmt.Println("Are these strings numeric?") strings := []string{"1", "3.14", "-100", "1e2", "NaN", "rose"} for _, s := range strings { fmt.Printf(" %4s -> %t\n", s, isNumeric(s)) } }  Output: Are these strings numeric? 1 -> true 3.14 -> true -100 -> true 1e2 -> true NaN -> true rose -> false  This uses both a library function and a custom one but only checks for integerness: package main import ( "fmt" "strconv" "unicode" ) func isInt(s string) bool { for _, c := range s { if !unicode.IsDigit(c) { return false } } return true } func main() { fmt.Println("Are these strings integers?") v := "1" b := false if _, err := strconv.Atoi(v); err == nil { b = true } fmt.Printf(" %3s -> %t\n", v, b) i := "one" fmt.Printf(" %3s -> %t\n", i, isInt(i)) }  Output: Are these strings integers? 1 -> true one -> false  ## Groovy Use the positional parser in java.text.NumberFormat. If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number. def isNumeric = { def formatter = java.text.NumberFormat.instance def pos = [0] as java.text.ParsePosition formatter.parse(it, pos) // if parse position index has moved to end of string // them the whole string was numeric pos.index == it.size() }  Test Program: println isNumeric('1') println isNumeric('-.555') println isNumeric('1,000,000') println isNumeric(' 1 1 1 1 ') println isNumeric('abcdef')  Output: true true true false false ## Haskell This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type with read or reads, and handle parsing failure appropriately. The task doesn't define which strings are considered "numeric", so we do Integers and Doubles, which should catch the most common cases (including hexadecimal 0x notation): isInteger s = case reads s :: [(Integer, String)] of [(_, "")] -> True _ -> False isDouble s = case reads s :: [(Double, String)] of [(_, "")] -> True _ -> False isNumeric :: String -> Bool isNumeric s = isInteger s || isDouble s  One can easily add isRational, isComplex etc. following the same pattern. Another way would be to use the Data.Char module, allowing code such as: areDigits = all isDigit isDigit selects ASCII digits i.e. '0'..'9' isOctDigit selects '0'..'7' isHexDigit selects '0'..'9','A'..'F','a'..'f'  so read s::Int (for instance) could be reliably used if string s passed these tests. ## Haxe Haxe has a built-in function that will convert a string to an integer, so we can use that to determine if the string is numeric or not. static function isNumeric(n:String):Bool { if (Std.parseInt(n) != null) //Std.parseInt converts a string to an int { return true; //as long as it results in an integer, the function will return true } else { return false; } }  ## HicEst  ! = bin + 2*int + 4*flt + 8*oct +16*hex + 32*sci isNumeric("1001") ! 27 = 1 1 0 1 1 0 isNumeric("123") ! 26 = 0 1 0 1 1 0 isNumeric("1E78") ! 48 = 0 0 0 0 1 1 isNumeric("-0.123") ! 4 = 0 0 1 0 0 1 isNumeric("-123.456e-78") ! 32 = 0 0 0 0 0 1 isNumeric(" 123") ! 0: leading blank isNumeric("-123.456f-78") ! 0: illegal character f FUNCTION isNumeric(string) ! true ( > 0 ), no leading/trailing blanks CHARACTER string b = INDEX(string, "[01]+", 128, Lbin) ! Lbin returns length found i = INDEX(string, "-?\d+", 128, Lint) ! regular expression: 128 f = INDEX(string, "-?\d+\.\d*", 128, Lflt) o = INDEX(string, "[0-7]+", 128, Loct) h = INDEX(string, "[0-9A-F]+", 128, Lhex) ! case sensitive: 1+128 s = INDEX(string, "-?\d+\.*\d*E[+-]*\d*", 128, Lsci) IF(anywhere) THEN ! 0 (false) by default isNumeric = ( b > 0 ) + 2*( i > 0 ) + 4*( f > 0 ) + 8*( o > 0 ) + 16*( h > 0 ) + 32*( s > 0 ) ELSEIF(boolean) THEN ! 0 (false) by default isNumeric = ( b + i + f + o + h + s ) > 0 ! this would return 0 or 1 ELSE L = LEN(string) isNumeric = (Lbin==L) + 2*(Lint==L) + 4*(Lflt==L) + 8*(Loct==L) + 16*(Lhex==L) + 32*(Lsci==L) ENDIF END ## i concept numeric(n) { number(n) errors { print(n, " is not numeric!") return } print(n, " is numeric :)") } software { numeric("1200") numeric("3.14") numeric("3/4") numeric("abcdefg") numeric("1234test") } ## Icon and Unicon The code writes a printable image of x whatever type it is and a statement about whether it is numeric or not. Icon and Unicon use success and failure instead of boolean functions, numeric(x) is built-in and returns x or fails. write(image(x), if numeric(x) then " is numeric." else " is not numeric")  ## IDL function isnumeric,input on_ioerror, false test = double(input) return, 1 false: return, 0 end  Could be called like this: if isnumeric('-123.45e-2') then print, 'yes' else print, 'no' ; ==> yes if isnumeric('picklejuice') then print, 'yes' else print, 'no' ; ==> no  ## J isNumeric=: _ ~: _ ". ] isNumericScalar=: 1 -: isNumeric TXT=: ,&' a scalar numeric value.' &.> ' is not';' represents' sayIsNumericScalar=: , TXT {::~ isNumericScalar  Examples of use:  isNumeric '152' 1 isNumeric '152 -3.1415926 Foo123' 1 1 0 isNumeric '42 foo42 4.2e1 4200e-2 126r3 16b2a 42foo' 1 0 1 1 1 1 0 isNumericScalar '152 -3.1415926 Foo123' 0 sayIsNumericScalar '-3.1415926' -3.1415926 represents a scalar numeric value.  ## Java Typically, you would use the 'parse' methods from either the Integer, Long, Float, or Double class, which will throw a NumberFormatException for ill-formed values. For example Integer.parseInt("12345")  Float.parseFloat("123.456")  The performance mark is somewhat negligible between a try-block and custom methods. public static void main(String[] args) { String value; value = "1234567"; System.out.printf("%-10s %b%n", value, isInteger(value)); value = "12345abc"; System.out.printf("%-10s %b%n", value, isInteger(value)); value = "-123.456"; System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); value = "-.456"; System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); value = "123."; System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); value = "123.abc"; System.out.printf("%-10s %b%n", value, isFloatingPoint(value)); } static boolean isInteger(String string) { String digits = "0123456789"; for (char character : string.toCharArray()) { if (!digits.contains(String.valueOf(character))) return false; } return true; } static boolean isFloatingPoint(String string) { /* at least one decimal-point */ int indexOf = string.indexOf('.'); if (indexOf == -1) return false; /* assure only 1 decimal-point */ if (indexOf != string.lastIndexOf('.')) return false; if (string.charAt(0) == '-' || string.charAt(0) == '+') { string = string.substring(1); indexOf--; } String integer = string.substring(0, indexOf); if (!integer.isEmpty()) { if (!isInteger(integer)) return false; } String decimal = string.substring(indexOf + 1); if (!decimal.isEmpty()) return isInteger(decimal); return true; }  1234567 true 12345abc false -123.456 true -.456 true 123. true 123.abc false  It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. If non-numeric strings are common, you're going to see a huge performance hit. public boolean isNumeric(String input) { try { Integer.parseInt(input); return true; } catch (NumberFormatException e) { // s is not numeric return false; } }  Alternative 1 : Check that each character in the string is number. Note that this will only works for integers. private static final boolean isNumeric(final String s) { if (s == null || s.isEmpty()) return false; for (int x = 0; x < s.length(); x++) { final char c = s.charAt(x); if (x == 0 && (c == '-')) continue; // negative if ((c >= '0') && (c <= '9')) continue; // 0 - 9 return false; // invalid } return true; // valid }  Alternative 2 : use a regular expression (a more elegant solution). public static boolean isNumeric(String inputData) { return inputData.matches("[-+]?\\d+(\\.\\d+)?"); }  Alternative 3 : use the positional parser in the java.text.NumberFormat object (a more robust solution). If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number. public static boolean isNumeric(String inputData) { NumberFormat formatter = NumberFormat.getInstance(); ParsePosition pos = new ParsePosition(0); formatter.parse(inputData, pos); return inputData.length() == pos.getIndex(); }  Alternative 4 : use the java.util.Scanner object. Very useful if you have to scan multiple entries. public static boolean isNumeric(String inputData) { Scanner sc = new Scanner(inputData); return sc.hasNextInt(); }  Scanner also has similar methods for longs, shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well as methods for integral types where you may input a base/radix other than 10 (10 is the default, which can be changed using the useRadix method). ## JavaScript A far better validator can be found on StackOverflow[1] function isNumeric(n) { return !isNaN(parseFloat(n)) && isFinite(n); } var value = "123.45e7"; // Assign string literal to value if (isNumeric(value)) { // value is a number } //Or, in web browser in address field: // javascript:function isNumeric(n) {return !isNaN(parseFloat(n)) && isFinite(n);}; value="123.45e4"; if(isNumeric(value)) {alert('numeric')} else {alert('non-numeric')}  ## jq In versions of jq that support try/catch, the simplest way to test if a string can be parsed as a number is: try tonumber catch false The above expression will emit the corresponding number, or false if there is none. Here then is a boolean filter which will also emit true for each input that is a number: def is_numeric: true and try tonumber catch false; ## Julia The function isnumber tests for strings that parse directly to numbers. This test excludes symbols, such as π and 1 + 1, that evaluate to numbers as well as certain elaborate numbers (large integers, rationals and complex numbers) whose literals parse to expressions that must be evaluated to yield numbers. using Printf isnumber(s::AbstractString) = tryparse(Float64, s) isa Number tests = ["1", "-121", "one", "pi", "1 + 1", "NaN", "1234567890123456789", "1234567890123456789123456789", "1234567890123456789123456789.0", "1.3", "1.4e10", "Inf", "1//2", "1.0 + 1.0im"] for t in tests fl = isnumber(t) ? "is" : "is not" @printf("%35s %s a direct numeric literal.\n", t, fl) end  Output:  1 is a direct numeric literal. -121 is a direct numeric literal. one is not a direct numeric literal. pi is not a direct numeric literal. 1 + 1 is not a direct numeric literal. NaN is a direct numeric literal. 1234567890123456789 is a direct numeric literal. 1234567890123456789123456789 is a direct numeric literal. 1234567890123456789123456789.0 is a direct numeric literal. 1.3 is a direct numeric literal. 1.4e10 is a direct numeric literal. Inf is a direct numeric literal. 1//2 is not a direct numeric literal. 1.0 + 1.0im is not a direct numeric literal.  ## Kotlin // version 1.1 fun isNumeric(input: String): Boolean = try { input.toDouble() true } catch(e: NumberFormatException) { false } fun main(args: Array<String>) { val inputs = arrayOf("152", "-3.1415926", "Foo123", "-0", "456bar", "1.0E10") for (input in inputs) println("$input is ${if (isNumeric(input)) "numeric" else "not numeric"}") }  Output: 152 is numeric -3.1415926 is numeric Foo123 is not numeric -0 is numeric 456bar is not numeric 1.0E10 is numeric  ## LabVIEW This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code. ## Lasso Works with: Lasso version 8 & 9 local(str='12345') string_isNumeric(#str) // true  Works with: Lasso version 9 '12345'->isdigit // true '1X34Q'->isdigit // false  ## Liberty BASIC DATA "PI", "0123", "-0123", "12.30", "-12.30", "123!", "0" DATA "0.0", ".123", "-.123", "12E3", "12E-3", "12+3", "end" while n$ <> "end"
read n$print n$, IsNumber(n$) wend end function IsNumber(string$)
on error goto [NotNumber]
string$= trim$(string$) 'check for float overflow n = val(string$)

'assume it is number and try to prove wrong
IsNumber = 1
for i = 1 to len(string$) select case mid$(string$, i, 1) case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" HasNumeric = 1 'to check if there are any digits case "e", "E" '"e" must not occur more than once 'must not occur before digits if HasE > 0 or HasNumeric = 0 then IsNumber = 0 exit for end if HasE = i 'store position of "e" HasNumeric = 0 'needs numbers after "e" case "-", "+" 'must be either first character or immediately after "e" '(HasE = 0 if no occurrences yet) if HasE <> i-1 then IsNumber = 0 exit for end if case "." 'must not have previous points and must not come after "e" if HasE <> 0 or HasPoint <> 0 then IsNumber = 0 exit for end if HasPoint = 1 case else 'no other characters allowed IsNumber = 0 exit for end select next i 'must have digits if HasNumeric = 0 then IsNumber = 0 [NotNumber] end function ## Lisaac "123457".is_integer.println; // write TRUE on stdin ## Logo show number? "-1.23 ; true ## Lua This will also accept strings like "0xFF" or "314.16e-2" as numbers. if tonumber(a) ~= nil then --it's a number end;  ## M2000 Interpreter We have to define our IsNumber() Version 2 handle decimal point character. For code M2000 use dot, but for input and output use the user specified decimal point, from OS. Function Str$(1.2) return a string with a dot always, but if we place a second parameter this change. Print str$(1.2, "") maybe return 1,2 and nor 1.2. Print str$(1.2, "#.00") maybe return 1.20 or 1,20. The reverse function is Val() which can take more characters so A Val("121mm") is 121, and with a second parameter we can interpret properly the decimal dot: Print Val("1.2", ".") always return 1.2 double. Print Val("1,2", ",")=1.2 return true, 1.2 is a m2000 number literal and always has a dot.

\\ version 2
Module Checkit {
function global isNumber(a$, de$=".") {
=false=true  ' return boolean
if de$="" then de$=str$(.1,".") ' get current decimal point character a$=trim$(ucase$(a$)) m=len(a$)
if m=0 then exit
c$=filter$(a$,"0123456789") if c$ = "" then {
=true
} else.if m>1 then {
\ may have -+ and ,
if m=2 then {
if not c$~"[-+\"+de$+"]" then break
} else {
if left$(c$,1 ) ~"[+-]" then c$=mid$(c$, 2) if not (c$=de$or c$=de$+"E" or c$ ~ de$+"E[+-]") then break if c$ ~ de$+"E[+-]" then if not (instr(a$,"E+")>0 or instr(a$,"E-")>0) then break } if de$<>"." then  a$=replace$(de$, ".", a$, 1,1)
try {inline "a="+a$+"=="+a$}
if valid(a) then =a = true=true  ' return boolean
}
}
Print isNumber("+1"), isnumber("-1"), isNumber("1+")=false, isnumber("1-")=false
Print isNumber(",1",","), isnumber("1,",","), isNumber(",0",","), isnumber("0,", ",")
Print isNumber(".1"), isnumber("1."), isNumber(".0"), isnumber("0.")
Print isNumber("+.1"), isnumber("-1."), isNumber(".12e+232"), isnumber("0.122e10")
Print isNumber("+.1a")=false, isnumber("asasa1212")=false, isNumber("1.2e43+23")=false, isnumber("0.122e10")
Print isNumber("1221.211.1221")=false, isnumber("1221e1212")=false, isNumber("1.2e4323")=false, isnumber("-.122e-10")
}
Checkit

From rev.31 Version 9.3 Val function update, to include a more quick version of above. We have to specify the dot char or write any two or more chars for dot to get integer part. Val function return number and in third argument (passing by reference by default) return first position in string after number. If string is empty or have no number then position is -1. If a number found position is >1. Leading spaces trimmed.

Function IsNumeric(a$) { def m =val(false->boolean) Try { if islet then { z=val(a$,letter$, m) } else.if isnum then { z=val(a$,number, m)
} else z=val(a$,"", m) =m>len(a$)
}
}
Function IsIntegerNumeric(a$) { def m =val(false->boolean) Try { z=val(a$,"Int", m)
=m>len(a$) } } Locale 1033 ' to use . as decimal, else we have to place 1033 or "." as second parameter Print isNumeric("+1"), isNumeric("-1"), isNumeric("1+")=false, isNumeric("1-")=false Print isNumeric(",1",","), isNumeric("1,",","), isNumeric(",0",","), isNumeric("0,", ",") Print isNumeric(".1"), isNumeric("1."), isNumeric(".0"), isNumeric("0.") Print isNumeric("+.1"), isNumeric("-1."), isNumeric(".12e+232"), isNumeric("0.122e10") Print isNumeric("+.1a")=false, isNumeric("asasa1212")=false, isNumeric("1.2e43+23")=false, isNumeric("0.122e10") Print isNumeric("1221.211.1221")=false, isNumeric("1221e1212")=false, isNumeric("1.2e4323")=false, isNumeric("-.122e-10") ## Maple isNumeric := proc(s) try if type(parse(s), numeric) then printf("The string is numeric."): else printf("The string is not numeric."): end if: catch: printf("The string is not numeric."): end try: end proc: ## Mathematica / Wolfram Language NumberQ[ToExpression["02553352000242"]]  ## MATLAB  function r = isnum(a) r = ~isnan(str2double(a)) end % tests disp(isnum(123)) % 1 disp(isnum("123")) % 1 disp(isnum("foo123")) % 0 disp(isnum("123bar")) % 0 disp(isnum("3.1415")) % 1  ## Maxima numberp(parse_string("170141183460469231731687303715884105727"));  ## MAXScript fn isNumeric str = ( try ( (str as integer) != undefined ) catch(false) ) isNumeric "123" ## min Works with: min version 0.19.3 ( dup (((int integer?) (pop false)) try) dip ((float float?) (pop false)) try or ) :numeric? ## MiniScript We rely on conversion to number returning a nonzero number, plus special checks for zero strings. Note that the val function is forgiving about additional characters after the number, so our function is too. isNumeric = function(s) return s == "0" or s == "-0" or val(s) != 0 end function print isNumeric("0") print isNumeric("42") print isNumeric("-3.14157") print isNumeric("5@*#!") print isNumeric("spam")  Output: 1 1 1 1 0 ## MIPS Assembly #$a0 char val
# $a1 address pointer #$a2 PERIOD_HIT_FLAG
# $a3 HAS_DIGITS_FLAG .data ### CHANGE THIS STRING TO TEST DIFFERENT ONES... ### string: .asciiz "-.1236" s_false: .asciiz "False" s_true: .asciiz "True" .text main: set_up: #test for 0th char == 45 or 46 or 48...57 la$a1,string
lb $a0,($a1)
beq $a0,45,loop # == '-' beq$a0,46,loop # == '.'
blt $a0,48,exit_false # isn't below the ascii range for chars '0'...'9' bgt$a0,57,exit_false # isn't above the ascii range for chars '0'...'9'
loop:
addi $a1,$a1,1
lb $a0,($a1)
beqz $a0,exit_true # test for \0 null char beq$a0,46,period_test #test for a duplicate period
blt $a0,48,exit_false #test for bgt$a0,57,exit_false
la $a3,1 #set the HAS_DIGITS flag. This line is only reached because the # tests for period and - both jump back to start. j loop exit_true: beqz$a3,exit_false
la $a0,s_true la$v0,4
syscall

li $v0,10 syscall exit_false: la$a0,s_false
la $v0,4 syscall li$v0,10
syscall

period_test:
beq $a2,1,exit_false li$a2,1
j loop

## Mirah

import java.text.NumberFormat
import java.text.ParsePosition
import java.util.Scanner

# this first example relies on catching an exception,
# which is bad style and poorly performing in Java
def is_numeric?(s:string)
begin
Double.parseDouble(s)
return true
rescue
return false
end
end

puts '123   is numeric' if is_numeric?('123')
puts '-123  is numeric' if is_numeric?('-123')
puts '123.1 is numeric' if is_numeric?('123.1')

puts 'nil   is not numeric' unless is_numeric?(nil)
puts "''    is not numeric" unless is_numeric?('')
puts 'abc   is not numeric' unless is_numeric?('abc')
puts '123-  is not numeric' unless is_numeric?('123-')
puts '1.2.3 is not numeric' unless is_numeric?('1.2.3')

# check every element of the string
def is_numeric2?(s: string)
if (s == nil || s.isEmpty())
return false
end
if (!s.startsWith('-'))
if s.contains('-')
return false
end
end

0.upto(s.length()-1) do |x|
c = s.charAt(x)
if ((x == 0) && (c == '-'.charAt(0)))
# negative number
elsif (c == '.'.charAt(0))
if (s.indexOf('.', x) > -1)
return false # more than one period
end
elsif (!Character.isDigit(c))
return false
end
end
true
end

puts '123   is numeric' if is_numeric2?('123')
puts '-123  is numeric' if is_numeric2?('-123')
puts '123.1 is numeric' if is_numeric2?('123.1')

puts 'nil   is not numeric' unless is_numeric2?(nil)
puts "''    is not numeric" unless is_numeric2?('')
puts 'abc   is not numeric' unless is_numeric2?('abc')
puts '123-  is not numeric' unless is_numeric2?('123-')
puts '1.2.3 is not numeric' unless is_numeric2?('1.2.3')

# use a regular  expression
def is_numeric3?(s:string)
s == nil || s.matches("[-+]?\\d+(\\.\\d+)?")
end

puts '123   is numeric' if is_numeric3?('123')
puts '-123  is numeric' if is_numeric3?('-123')
puts '123.1 is numeric' if is_numeric3?('123.1')

puts 'nil   is not numeric' unless is_numeric3?(nil)
puts "''    is not numeric" unless is_numeric3?('')
puts 'abc   is not numeric' unless is_numeric3?('abc')
puts '123-  is not numeric' unless is_numeric3?('123-')
puts '1.2.3 is not numeric' unless is_numeric3?('1.2.3')

#  use the positional parser in the java.text.NumberFormat object
# (a more robust solution). If, after parsing, the parse position is at
# the end of the string, we can deduce that the entire string was a
# valid number.
def is_numeric4?(s:string)
return false if s == nil
formatter = NumberFormat.getInstance()
pos = ParsePosition.new(0)
formatter.parse(s, pos)
s.length() == pos.getIndex()
end

puts '123   is numeric' if is_numeric4?('123')
puts '-123  is numeric' if is_numeric4?('-123')
puts '123.1 is numeric' if is_numeric4?('123.1')

puts 'nil   is not numeric' unless is_numeric4?(nil)
puts "''    is not numeric" unless is_numeric4?('')
puts 'abc   is not numeric' unless is_numeric4?('abc')
puts '123-  is not numeric' unless is_numeric4?('123-')
puts '1.2.3 is not numeric' unless is_numeric4?('1.2.3')

# use the java.util.Scanner object. Very useful if you have to
# scan multiple entries. Scanner also has similar methods for longs,
# shorts, bytes, doubles, floats, BigIntegers, and BigDecimals as well
# as methods for integral types where you may input a base/radix other than
# 10 (10 is the default, which can be changed using the useRadix method).
def is_numeric5?(s:string)
return false if s == nil
Scanner sc = Scanner.new(s)
sc.hasNextDouble()
end

puts '123   is numeric' if is_numeric5?('123')
puts '-123  is numeric' if is_numeric5?('-123')
puts '123.1 is numeric' if is_numeric5?('123.1')

puts 'nil   is not numeric' unless is_numeric5?(nil)
puts "''    is not numeric" unless is_numeric5?('')
puts 'abc   is not numeric' unless is_numeric5?('abc')
puts '123-  is not numeric' unless is_numeric5?('123-')
puts '1.2.3 is not numeric' unless is_numeric5?('1.2.3')

## mIRC Scripting Language

Works with: mIRC
var %value = 3
if (%value isnum) {
echo -s %value is numeric.
}

## Modula-3

MODULE Numeric EXPORTS Main;

IMPORT IO, Fmt, Text;

PROCEDURE isNumeric(s: TEXT): BOOLEAN =
BEGIN
FOR i := 0 TO Text.Length(s) DO
WITH char = Text.GetChar(s, i) DO
IF i = 0 AND char = '-' THEN
EXIT;
END;
IF char >= '0' AND char <= '9' THEN
EXIT;
END;
RETURN FALSE;
END;
END;
RETURN TRUE;
END isNumeric;

BEGIN
IO.Put("isNumeric(152) = " & Fmt.Bool(isNumeric("152")) & "\n");
IO.Put("isNumeric(-3.1415926) = " & Fmt.Bool(isNumeric("-3.1415926")) & "\n");
IO.Put("isNumeric(Foo123) = " & Fmt.Bool(isNumeric("Foo123")) & "\n");
END Numeric.

Output:
isNumeric(152) = TRUE
isNumeric(-3.1415926) = TRUE
isNumeric(Foo123) = FALSE


## MUMPS

In MUMPS, strings are automatically converted to numbers when a unary or binary arithmetic operator works upon them. If there are no leading digits, a string converts to zero. If there a string of digits followed by an "e" or an "E" followed in turn by more digits, the numbers after the letter are treated as an exponent.

Examples from command line:

USER>WRITE +"1"
1
USER>WRITE +"1A"
1
USER>WRITE +"A1"
0
USER>WRITE +"1E"
1
USER>WRITE +"1E2"
100
USER>WRITE +"1EA24"
1
USER>WRITE +"1E3A"
1000
USER>WRITE +"1E-3"
.001


WriteLine($"$not is numeric: $(IsNumeric(not))"); } }  ## NetRexx /* NetRexx */ options replace format comments java crossref symbols nobinary numeric digits 20 loop n_ over getTestData() -- could have used n_.datatype('N') directly here... if isNumeric(n_) then msg = 'numeric' else msg = 'not numeric' say ('"'n_'"').right(25)':' msg end n_ return -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Pointless in NetRexx; the DATATYPE built-in-function is more powerful! method isNumeric(testString) public static returns boolean return testString.datatype('N') -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method getTestData() private static returns Rexx[] -- Coercing numbers into the Rexx type has the effect of converting them to strings. -- NetRexx will still perform arithmetic on Rexx strings if those strings represent numbers. -- Notice that whitespace between the sign and the number are ignored even when inside a string constant testData = [ Rexx - ' one and a half', 1, 1.5, 1.5e+27, ' 1 ', ' 1.5 ', ' 1.5e+27 ', - '-one and a half', - 1, - 1.5, - 1.5e-27, ' - 1 ', '- 1.5 ', '- 1.5e-27 ', - '+one and a half', + 1, + 1.5, + 1.5e+27, ' + 1 ', '+ 1.5 ', '+ 1.5e+27 ', - 'Math Constants', - Math.PI, Math.E, - -Math.PI, -Math.E, - +Math.PI, +Math.E, - 'Numeric Constants', - Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY - ] return testData  Output:  " one and a half": not numeric "1": numeric "1.5": numeric "1.5e+27": numeric " 1 ": numeric " 1.5 ": numeric " 1.5e+27 ": numeric "-one and a half": not numeric "-1": numeric "-1.5": numeric "-1.5E-27": numeric " - 1 ": numeric "- 1.5 ": numeric "- 1.5e-27 ": numeric "+one and a half": not numeric "1": numeric "1.5": numeric "1.5E+27": numeric " + 1 ": numeric "+ 1.5 ": numeric "+ 1.5e+27 ": numeric "Math Constants": not numeric "3.141592653589793": numeric "2.718281828459045": numeric "-3.141592653589793": numeric "-2.718281828459045": numeric "3.141592653589793": numeric "2.718281828459045": numeric "Numeric Constants": not numeric "NaN": not numeric "Infinity": not numeric "Infinity": not numeric  ## Nim import strutils proc isNumeric(s: string): bool = try: discard s.parseFloat() result = true except ValueError: result = false const Strings = ["1", "3.14", "-100", "1e2", "Inf", "rose"] for s in Strings: echo s, " is ", if s.isNumeric(): "" else: "not ", "numeric"  We could prefer to use the “parsutils” module which avoids the exception: import parseutils proc isNumeric(s: string): bool = var x: float s.parseFloat(x) == s.len const Strings = ["1", "3.14", "-100", "1e2", "Inf", "rose"] for s in Strings: echo s, " is ", if s.isNumeric(): "" else: "not ", "numeric"  Output: 1 is numeric 3.14 is numeric -100 is numeric 1e2 is numeric Inf is numeric rose is not numeric ## Objeck class Numeric { function : Main(args : String[]) ~ Nil { if(args->Size() = 1) { IsNumeric(args[0])->PrintLine(); }; } function : IsNumeric(str : String) ~ Bool { return str->IsFloat(); } } ## Objective-C Works with: GCC Works with: OpenStep Works with: GNUstep The NSScanner class supports scanning of strings for various types. The scanFloat method will return YES if the string is numeric, even if the number is actually too long to be contained by the precision of a float. if( [[NSScanner scannerWithString:@"-123.4e5"] scanFloat:NULL] ) NSLog( @"\"-123.4e5\" is numeric" ); else NSLog( @"\"-123.4e5\" is not numeric" ); if( [[NSScanner scannerWithString:@"Not a number"] scanFloat:NULL] ) NSLog( @"\"Not a number\" is numeric" ); else NSLog( @"\"Not a number\" is not numeric" ); // prints: "-123.4e5" is numeric // prints: "Not a number" is not numeric  The following function can be used to check if a string is numeric "totally"; this is achieved by checking if the scanner reached the end of the string after the float is parsed. BOOL isNumeric(NSString *s) { NSScanner *sc = [NSScanner scannerWithString: s]; if ( [sc scanFloat:NULL] ) { return [sc isAtEnd]; } return NO; }  If we want to scan by hand, we could use a function like the following, that checks if a number is an integer positive or negative number; spaces can appear at the beginning, but not after the number, and the '+' or '-' can appear only attached to the number ("+123" returns YES, but "+ 123" returns NO). BOOL isNumericI(NSString *s) { NSUInteger len = [s length]; NSUInteger i; BOOL status = NO; for(i=0; i < len; i++) { unichar singlechar = [s characterAtIndex: i]; if ( (singlechar == ' ') && (!status) ) { continue; } if ( ( singlechar == '+' || singlechar == '-' ) && (!status) ) { status=YES; continue; } if ( ( singlechar >= '0' ) && ( singlechar <= '9' ) ) { status = YES; } else { return NO; } } return (i == len) && status; }  Here we assumed that in the internal encoding of a string (that should be Unicode), 1 comes after 0, 2 after 1 and so on until 9. Another way could be to get the C String from the NSString object, and then the parsing would be the same of the one we could do in standard C, so this path is not given. ## OCaml This function is not particularly useful in a statically typed language. Instead, one would just attempt to convert the string to the desired type and handle parsing failure appropriately. The task doesn't define which strings are considered "numeric", so we do ints and floats, which should catch the most common cases: let is_int s = try ignore (int_of_string s); true with _ -> false let is_float s = try ignore (float_of_string s); true with _ -> false let is_numeric s = is_int s || is_float s  ## Octave The builtin function isnumeric return true (1) if the argument is a data of type number; the provided function isnum works the same for numeric datatype, while if another type is passed as argument, it tries to convert it to a number; if the conversion fails, it means it is not a string representing a number. function r = isnum(a) if ( isnumeric(a) ) r = 1; else r = ~isnan(str2double(a)); endif endfunction % tests disp(isnum(123)) % 1 disp(isnum("123")) % 1 disp(isnum("foo123")) % 0 disp(isnum("123bar")) % 0 disp(isnum("3.1415")) % 1  ## Odin package main import "core:strconv" import "core:fmt" is_numeric :: proc(s: string) -> bool { _, ok := strconv.parse_f32(s) return ok } main :: proc() { strings := []string{"1", "3.14", "-100", "1e2", "Inf", "rose"} for s in strings { fmt.println(s, "is", is_numeric(s) ? "numeric" : "not numeric") } } /* Output: 1 is numeric 3.14 is numeric -100 is numeric 1e2 is numeric Inf is not numeric rose is not numeric */  ## Oz fun {IsNumeric S} {String.isInt S} orelse {String.isFloat S} end ## PARI/GP isNumeric(s)={ my(t=type(eval(s))); t == "t_INT" || t == "T_REAL" }; ## Pascal See Delphi or Free Pascal. ## PeopleCode Built-In Function Syntax IsNumber(Value) Description Use the IsNumber function to determine if Value contains a valid numeric value. Numeric characters include sign indicators and comma and period decimal points. To determine if a value is a number and if it's in the user's local format, use the IsUserNumber function. Parameters Value Specify a string you want to search to determine if it is a valid number. Returns A Boolean value: True if Value contains a valid numeric value, False otherwise. Example &Value = Get Field().Value; If IsNumber(&Value) Then /* do numeric processing */ Else /* do non-numeric processing */ End-if; ## Perl Works with: Perl version 5.8 use Scalar::Util qw(looks_like_number); print looks_like_number($str) ? "numeric" : "not numeric\n";

Works with: Perl version 5.8

Quoting from perlfaq4:

How do I determine whether a scalar is a number/whole/integer/float?

Assuming that you don't care about IEEE notations like "NaN" or "Infinity", you probably just want to use a regular expression.

if (/\D/)            { print "has nondigits\n" }
if (/^\d+\z/)         { print "is a whole number\n" }
if (/^-?\d+\z/)       { print "is an integer\n" }
if (/^[+-]?\d+\z/)    { print "is a +/- integer\n" }
if (/^-?\d+\.?\d*\z/) { print "is a real number\n" }
if (/^-?(?:\d+(?:\.\d*)?&\.\d+)\z/) { print "is a decimal number\n" }
if (/^([+-]?)(?=\d&\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?\z/)
{ print "a C float\n" }


There are also some commonly used modules for the task. Scalar::Util (distributed with 5.8) provides access to Perl's internal function "looks_like_number" for determining whether a variable looks like a number. Data::Types exports functions that validate data types using both the above and other regular expressions. Thirdly, there is "Regexp::Common" which has regular expressions to match various types of numbers. Those three modules are available from the CPAN.

If you're on a POSIX system, Perl supports the "POSIX::strtod" function. Its semantics are somewhat cumbersome, so here's a "getnum" wrapper function for more convenient access. This function takes a string and returns the number it found, or "undef" for input that isn't a C float. The "is_numeric" function is a front end to "getnum" if you just want to say, Is this a float?

sub getnum {
use POSIX;
my $str = shift;$str =~ s/^\s+//;
$str =~ s/\s+$//;
$! = 0; my($num, $unparsed) = strtod($str);
if (($str eq '') && ($unparsed != 0) && $!) { return undef; } else { return$num;
}
}

if(is_numeric(trim($string))) { } ?>  ## PicoLisp The 'format' function can be used for that. It returns NIL if the given string is not a legal number : (format "123") -> 123 : (format "123a45") -> NIL : (format "-123.45" 4) -> 1234500 ## Pike the sscanf format %f will find any kind of number. the %s before and after make sure the number is not surrounded by other text. int(0..1) is_number(string s) { array test = array_sscanf(s, "%s%f%s"); if (sizeof(test) == 3 && test[1] && !sizeof(test[0]) && !sizeof(test[2]) ) return true; else return false; } string num = "-1.234" is_number(num); -> true  ## PL/I is_numeric: procedure (text) returns (bit (1)); declare text character (*); declare x float; on conversion go to done; get string(text) edit (x) (E(length(text),0)); return ('1'b); done: return ('0'b); end is_numeric; 5 '1'B 6.7 '1'B -8.9 '1'B -4e3 '1'B 4A37 '0'B  ## PL/SQL FUNCTION IsNumeric( value IN VARCHAR2 ) RETURN BOOLEAN IS help NUMBER; BEGIN help := to_number( value ); return( TRUE ); EXCEPTION WHEN others THEN return( FALSE ); END;  Value VARCHAR2( 10 ) := '123'; IF( IsNumeric( Value ) ) THEN NULL; END IF;  ## Plain English The following decider exists in the noodle To decide if a string is any numeric literal: and is used to resolve the If clause If the string is any numeric literal, in this solution. To run: Start up. Show whether "cat" is numeric. Show whether "3" is numeric. Show whether "+3" is numeric. Show whether "-123" is numeric. Show whether "123,456" is numeric. Show whether "11/5" is numeric. Show whether "-26-1/3" is numeric. Show whether "+26-1/3" is numeric. Show whether "1/0" is numeric. \in Plain English, 1/0 is 0. Don't tell the mathematicians! Show whether "3.14159" is numeric. \floating point is not implemented in Plain English. Wait for the escape key. Shut down. To show whether a string is numeric: Write the string then " -> " on the console without advancing. If the string is any numeric literal, write "yes" on the console; exit. Write "no" on the console. Output: cat -> no 3 -> yes +3 -> yes -123 -> yes 123,456 -> no 11/5 -> yes -26-1/3 -> yes +26-1/3 -> yes 1/0 -> yes 3.14159 -> no  ## PowerShell Note: PowerShell 1.0 does not support 'try' THis simply tries arithmetic with the argument and if that fails, false is returned. function isNumeric ($x) {
try {
0 + $x | Out-Null return$true
} catch {
return $false } }  But this one doesn't work for strings like "8." though a . is appended it returns true! Alternatively, you can use the static System.Int32.TryParse() method in the .NET framework. function isNumeric ($x) {
$x2 = 0$isNum = [System.Int32]::TryParse($x, [ref]$x2)
return $isNum }  ## Prolog Works with: SWI-Prolog version 7 The code: numeric_string(String) :- atom_string(Atom, String), atom_number(Atom, _).  A predicate to test the code: test_strings(Strings) :- forall( member(String, Strings), ( ( numeric_string(String) -> Result = a ; Result = 'not a' ), format('~w is ~w number.~n', [String, Result]) ) ).  Example of using the test predicate: ?- test_strings(["123", "0.123", "-123.1", "NotNum", "1."]). 123 is a number. 0.123 is a number. -123.1 is a number. NotNum is not a number. 1. is not a number. true.  ## PureBasic This routine parses the string to verify it's a number. It returns 1 if string is numeric, 0 if it is not. The character used as the decimal separator may be specified if desired. Procedure IsNumeric(InString.s, DecimalCharacter.c = '.') #NotNumeric = #False #IsNumeric = #True InString = Trim(InString) Protected IsDecimal, CaughtDecimal, CaughtE Protected IsSignPresent, IsSignAllowed = #True, CountNumeric Protected *CurrentChar.Character = @InString While *CurrentChar\c Select *CurrentChar\c Case '0' To '9' CountNumeric + 1 IsSignAllowed = #False Case DecimalCharacter If CaughtDecimal Or CaughtE Or CountNumeric = 0 ProcedureReturn #NotNumeric EndIf CountNumeric = 0 CaughtDecimal = #True IsDecimal = #True Case '-', '+' If IsSignPresent Or Not IsSignAllowed: ProcedureReturn #NotNumeric: EndIf IsSignPresent = #True Case 'E', 'e' If CaughtE Or CountNumeric = 0 ProcedureReturn #NotNumeric EndIf CaughtE = #True CountNumeric = 0 CaughtDecimal = #False IsSignPresent = #False IsSignAllowed = #True Default ProcedureReturn #NotNumeric EndSelect *CurrentChar + SizeOf(Character) Wend If CountNumeric = 0: ProcedureReturn #NotNumeric: EndIf ProcedureReturn #IsNumeric EndProcedure If OpenConsole() PrintN("'+3183.31151E+321' = " + Str(IsNumeric("+3183.31151E+321"))) PrintN("'-123456789' = " + Str(IsNumeric("-123456789"))) PrintN("'123.45.6789+' = " + Str(IsNumeric("123.45.6789+"))) PrintN("'-e' = " + Str(IsNumeric("-e"))) Print(#CRLF$ + #CRLF$+ "Press ENTER to exit") Input() CloseConsole() EndIf  Output: '+3183.31151E+321' = 1 '-123456789' = 1 '123.45.6789+' = 0 '-e' = 0 ## Python ### Python: Simple int/float def is_numeric(s): try: float(s) return True except (ValueError, TypeError): return False is_numeric('123.0')  Or for positive integers only: '123'.isdigit()  ### Python: Most numeric literals Including complex, hex, binary, and octal numeric literals we get: def is_numeric(literal): """Return whether a literal can be parsed as a numeric value""" castings = [int, float, complex, lambda s: int(s,2), #binary lambda s: int(s,8), #octal lambda s: int(s,16)] #hex for cast in castings: try: cast(literal) return True except ValueError: pass return False  Sample use, including value parsed, its type, and standard method str.isnumeric(): def numeric(literal): """Return value of numeric literal or None if can't parse a value""" castings = [int, float, complex, lambda s: int(s,2), #binary lambda s: int(s,8), #octal lambda s: int(s,16)] #hex for cast in castings: try: return cast(literal) except ValueError: pass return None tests = [ '0', '0.', '00', '123', '0123', '+123', '-123', '-123.', '-123e-4', '-.8E-04', '0.123', '(5)', '-123+4.5j', '0b0101', ' +0B101 ', '0o123', '-0xABC', '0x1a1', '12.5%', '1/2', '½', '3¼', 'π', 'Ⅻ', '1,000,000', '1 000', '- 001.20e+02', 'NaN', 'inf', '-Infinity'] for s in tests: print("%14s -> %-14s %-20s is_numeric: %-5s str.isnumeric: %s" % ( '"'+s+'"', numeric(s), type(numeric(s)), is_numeric(s), s.isnumeric() ))  Output:  "0" -> 0 <class 'int'> is_numeric: True str.isnumeric: True "0." -> 0.0 <class 'float'> is_numeric: True str.isnumeric: False "00" -> 0 <class 'int'> is_numeric: True str.isnumeric: True "123" -> 123 <class 'int'> is_numeric: True str.isnumeric: True "0123" -> 123 <class 'int'> is_numeric: True str.isnumeric: True "+123" -> 123 <class 'int'> is_numeric: True str.isnumeric: False "-123" -> -123 <class 'int'> is_numeric: True str.isnumeric: False "-123." -> -123.0 <class 'float'> is_numeric: True str.isnumeric: False "-123e-4" -> -0.0123 <class 'float'> is_numeric: True str.isnumeric: False "-.8E-04" -> -8e-05 <class 'float'> is_numeric: True str.isnumeric: False "0.123" -> 0.123 <class 'float'> is_numeric: True str.isnumeric: False "(5)" -> (5+0j) <class 'complex'> is_numeric: True str.isnumeric: False "-123+4.5j" -> (-123+4.5j) <class 'complex'> is_numeric: True str.isnumeric: False "0b0101" -> 5 <class 'int'> is_numeric: True str.isnumeric: False " +0B101 " -> 5 <class 'int'> is_numeric: True str.isnumeric: False "0o123" -> 83 <class 'int'> is_numeric: True str.isnumeric: False "-0xABC" -> -2748 <class 'int'> is_numeric: True str.isnumeric: False "0x1a1" -> 417 <class 'int'> is_numeric: True str.isnumeric: False "12.5%" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "1/2" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "½" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True "3¼" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True "π" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "Ⅻ" -> None <class 'NoneType'> is_numeric: False str.isnumeric: True "1,000,000" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "1 000" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "- 001.20e+02" -> None <class 'NoneType'> is_numeric: False str.isnumeric: False "NaN" -> nan <class 'float'> is_numeric: True str.isnumeric: False "inf" -> inf <class 'float'> is_numeric: True str.isnumeric: False "-Infinity" -> -inf <class 'float'> is_numeric: True str.isnumeric: False ### Python: Regular expressions import re numeric = re.compile('[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?') is_numeric = lambda x: numeric.fullmatch(x) != None is_numeric('123.0')  ## Quackery  [ char . over find tuck over found iff [ swap pluck drop ] else nip ] is -point ($ --> $) [ -point$->n nip ]           is numeric ( $--> b ) [ dup echo$ say " is"
numeric not if say " not"
say " a valid number." cr ] is task    ( $--> )$ "152"        task
$"-3.1415926" task$ "Foo123"     task
Output:
152 is a valid number.
-3.1415926 is a valid number.
Foo123 is not a valid number.

## R

> strings <- c("152", "-3.1415926", "Foo123")
> suppressWarnings(!is.na(as.numeric(strings)))
[1]  TRUE  TRUE FALSE


## Racket

(define (string-numeric? s) (number? (string->number s)))


Or, since all non-#f are true:

(define string-numeric? string->number)


## Raku

(formerly Perl 6)

Works with: Rakudo version 2017.11

Raku tries very hard to DWIM (do what I mean). As part of that, numeric strings are by default stored as allomorphic types which can be used as numbers or strings without any conversion. If we truly want to operate on strings, we have to explicitly coerce the allomorphs to strings. A subtlety that may not be immediately apparent, whitespace, empty strings and null strings may be treated as (False) boolean values in Raku, however booleans are allomorphic to numeric, so empty strings will coerce to a numeric value (0), and return as numeric unless specifically checked for. Interestingly, the actual strings 'True' and 'False' don't evaluate as numeric. (because there are no String | Boolean allomorphs.)

Note: These routines are usable for most cases but won't detect unicode non-digit numeric forms; E.G. vulgar fractions, Roman numerals, circled numbers, etc. If it is necessary to detect those as numeric, a full fledged grammar may be necessary.

sub is-number-w-ws( Str $term --> Bool ) { # treat Falsey strings as numeric$term.Numeric !~~ Failure;
}

sub is-number-wo-ws( Str $term --> Bool ) { # treat Falsey strings as non-numeric ?($term ~~ / \S /) && $term.Numeric !~~ Failure; } say " Coerce Don't coerce"; say ' String whitespace whitespace'; printf "%10s %8s %11s\n", "<$_>", .&is-number-w-ws, .&is-number-wo-ws for
(|<1 1.2 1.2.3 -6 1/2 12e B17 1.3e+12 1.3e12 -2.6e-3 zero 0x 0xA10 0b1001 0o16
0o18 2+5i True False Inf NaN 0x10.50 0b102 0o_5_3 ௫௯>, '  12  ', '1 1 1', '', ' ' ).map: *.Str;

               Coerce     Don't coerce
String   whitespace    whitespace
<1>      True         True
<1.2>      True         True
<1.2.3>     False        False
<-6>      True         True
<1/2>      True         True
<12e>     False        False
<B17>     False        False
<1.3e+12>      True         True
<1.3e12>      True         True
<-2.6e-3>      True         True
<zero>     False        False
<0x>     False        False
<0xA10>      True         True
<0b1001>      True         True
<0o16>      True         True
<0o18>     False        False
<2+5i>      True         True
<True>     False        False
<False>     False        False
<Inf>      True         True
<NaN>      True         True
<0x10.50>      True         True
<0b102>     False        False
<0o_5_3>      True         True
<௫௯>      True         True
<   12  >      True         True
<1 1 1>     False        False
<>      True        False
< >      True        False

## RapidQ

isnumeric
$Typecheck on Defint FALSE, TRUE FALSE = 0 TRUE = NOT FALSE Function isNumeric(s as string, optchar as string) as integer If len(s) = 0 then Result = FALSE Exit Function End If if instr(s,"+") > 1 then Result = FALSE exit function end if if instr(s,"-") > 1 then Result = FALSE exit function end if Defint i, ndex = 0 For i = 1 to len(s) select case asc(mid$(s,i,1))
case 43   '+
case 45   '-
case 46 '.
if ndex = 1 then
Result = FALSE
Exit function
end if
ndex = 1
case 48 to 57  '0 to 9
case else
if instr(optchar,(mid$(s,i,1))) = 0 then Result = FALSE exit function end if end select next Result = TRUE End Function '============================================================ 'Begin '============================================================ showmessage (str$(isNumeric("-152.34","")))
end

## REBOL

REBOL [
Title: "Is Numeric?"
URL: http://rosettacode.org/wiki/IsNumeric
]

; Built-in.

numeric?: func [x][not error? try [to-decimal x]]

; Parse dialect for numbers.

sign:   [0 1 "-"]
digit:  charset "0123456789"
int:    [some digit]
float:  [int "." int]
number: [
sign float |
]

pnumeric?: func [x][parse x number]

; Test cases.

cases: parse {
10 -99
10.43 -12.04
1e99 1.0e10 -10e3 -9.12e7 2e-4 -3.4E-5
3phase  Garkenhammer  e  n3v3r  phase3
} none
foreach x cases [print [x  numeric? x  pnumeric? x]]


## Retro

Retro does not have floating point numbers as part of the core system. For others, this can be done with:

'123 a:from-string TRUE [ swap c:digit? and ] a:reduce

## REXX

/*REXX program determines if a string is numeric,  using REXX's rules for numbers.      */
yyy=' -123.78'                                   /*or some such.                        */

/*strings below are all numeric (REXX).*/
zzz= ' -123.78 '
zzz= '-123.78'
zzz= '2'
zzz= "2"
zzz= 2
zzz= '000000000004'
zzz= '+5'
zzz=  +5
zzz= ' +6 '
zzz= ' + 7 '
zzz= ' - 8 '
zzz= ' - .9'
zzz= '- 19.'
zzz= '.7'
zzz=  .7
zzz= '2e3'
zzz= 47e567
zzz= '2e-3'
zzz= '1.2e1'
zzz= ' .2E6'
zzz= ' 2.e5 '
zzz= '       +1.2E0002 '
zzz= '       +1.2e+002 '
zzz= ' +0000001.200e+002 '
zzz= ' - 000001.200e+002 '
zzz= ' - 000008.201e-00000000000000002 '

/*Note:  some REXX interpreters allow use of tab chars as blanks.  */

/*all statements below are equivalent.*/

if \datatype(yyy, 'n')        then say 'oops, not numeric:'  yyy
if \datatype(yyy, 'N')        then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'N')        then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'numeric')  then say 'oops, not numeric:'  yyy
if ¬datatype(yyy, 'nimrod.')  then say 'oops, not numeric:'  yyy
if  datatype(yyy) \== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) /== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) ¬== 'NUM'   then say 'oops, not numeric:'  yyy
if  datatype(yyy) ¬=  'NUM'   then say 'oops, not numeric:'  yyy

/*note:  REXX only looks at the first char for DATATYPE's  2nd argument.*/

/*note:  some REXX interpreters don't support the  ¬  (not)  character. */


## Ring

see isdigit("0123456789") + nl +        # print 1
isdigit("0123a")                    # print 0

## RPL

This one-liner returns 1 if the string is either a real number, a complex number or a binary integer - and zero otherwise.

≪ IFERR STR→ THEN DROP 0 ELSE TYPE { 0 1 10 } SWAP POS SIGN END ≫ ‘NUM?’ STO


## Ruby

def is_numeric?(s)
begin
Float(s)
rescue
false # not numeric
else
true # numeric
end
end


or more compact:

def is_numeric?(s)
!!Float(s) rescue false
end


NB! Since Ruby 2.6 you no longer need rescue:

def is_numeric?(s)
!!Float(s, exception: false)
end


Adding exception: false will make it return nil instead.

sample

strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e)
strings.each do |str|
puts "%9p => %s" % [str, is_numeric?(str)]
end

Output:
      "0" => true
"0.0" => true
"-123" => true
"abc" => false
"0x10" => true
"0xABC" => true
"123a" => false
"-123e3" => true
"0.1E-5" => true
"50e" => false


## Run BASIC

print isNumeric("123")
print isNumeric("1ab")

' ------------------------
' Numeric Check
' 1 = good
' ------------------------
FUNCTION isNumeric(f$) isNumeric = 1 f$	= trim$(f$)
if left$(f$,1) = "-" or left$(f$,1) = "+" then f$= mid$(f$,2) for i = 1 to len(f$)
d$= mid$(f$,i,1) if d$ = "," then goto [nxtDigit]
if d$= "." then if dot$ = "." then isNumeric = 0
dot$= "." goto [nxtDigit] end if if (d$ < "0") or (d$> "9") then isNumeric = 0 [nxtDigit] next i END FUNCTION 123 1 1ab 0 ## Rust // This function is not limited to just numeric types but rather anything that implements the FromStr trait. fn parsable<T: FromStr>(s: &str) -> bool { s.parse::<T>().is_ok() }  ## Scala import scala.util.control.Exception.allCatch def isNumber(s: String): Boolean = (allCatch opt s.toDouble).isDefined  def isNumeric(input: String): Boolean = input.forall(_.isDigit)  Or a more complete version, using a complex regular expression: def isNumeric2(str: String): Boolean = { str.matches(s"""[+-]?((\d+(e\d+)?[lL]?)|(((\d+(\.\d*)?)|(\.\d+))(e\d+)?[fF]?))""") }  Or using the built-in number parsing and catching exceptions: def isNumeric(str: String): Boolean = { !throwsNumberFormatException(str.toLong) || !throwsNumberFormatException(str.toDouble) } def throwsNumberFormatException(f: => Any): Boolean = { try { f; false } catch { case e: NumberFormatException => true } }  ## Scheme string->number returns #f when the string is not numeric and otherwise the number, which is non-#f and therefore true. (define (numeric? s) (string->number s))  ## Seed7 The function isNumeric uses the function getNumber from the library scanstri.s7i. GetNumber reads a numeric literal from a string. The numeric literal is removed from the input string. $ include "seed7_05.s7i";
include "scanstri.s7i";

const func boolean: isNumeric (in var string: stri) is func
result
var boolean: isNumeric is FALSE;
local
var string: numberStri is "";
begin
numberStri := getNumber(stri);
isNumeric := stri = "";
end func;

## Sidef

There is the the String.looks_like_number method, which returns true when a given strings looks like a number:

say "0.1E-5".looks_like_number;       #=> true


Alternatively, we can use regular expressions to determine this:

func is_numeric(s) {
(s ~~ /^[+-]?+(?=\.?[0-9])[0-9_]*+(?:\.[0-9_]++)?(?:[Ee](?:[+-]?+[0-9_]+))?\z/) ||
(s ~~ /^0(?:b[10_]*|x[0-9A-Fa-f_]*|[0-9_]+\b)\z/)
}


Sample:

var strings = %w(0 0.0 -123 abc 0x10 0xABC 123a -123e3 0.1E-5 50e);
for str in strings {
say ("%9s => %s" % (str, is_numeric(str)))
}

Output:
        0 => true
0.0 => true
-123 => true
abc => false
0x10 => true
0xABC => true
123a => false
-123e3 => true
0.1E-5 => true
50e => false


## Simula

Simula uses the '&' instead of 'e' or 'E' for the exponent part of a floating point decimal number.

BEGIN

BOOLEAN PROCEDURE ISNUMERIC(W); TEXT W;
BEGIN
BOOLEAN PROCEDURE MORE;
MORE := W.MORE;
CHARACTER PROCEDURE NEXT;
NEXT := IF MORE THEN W.GETCHAR ELSE CHAR(0);
CHARACTER PROCEDURE LAST;
LAST := IF W.LENGTH = 0
THEN CHAR(0)
ELSE W.SUB(W.LENGTH,1).GETCHAR;
CHARACTER CH;
W.SETPOS(1);
IF MORE THEN
BEGIN
CH := NEXT;
IF CH = '-' OR CH = '+' THEN CH := NEXT;
WHILE DIGIT(CH) DO CH := NEXT;
IF CH = '.' THEN
BEGIN
CH := NEXT;
IF NOT DIGIT(CH) THEN GOTO L;
WHILE DIGIT(CH) DO CH := NEXT;
END;
IF CH = '&' THEN
BEGIN
CH := NEXT;
IF CH = '-' OR CH = '+' THEN CH := NEXT;
WHILE DIGIT(CH) DO CH := NEXT;
END;
END;
L:  ISNUMERIC := (W.LENGTH > 0) AND THEN (NOT MORE) AND THEN DIGIT(LAST);
END;

REAL X;
TEXT T;
FOR X := 0, -3.1415, 2.768&+31, 5&10, .5, 5.&10 DO
BEGIN
OUTREAL(X, 10, 20);
OUTIMAGE;
END;

OUTIMAGE;

FOR T :- "0", "-3.1415", "2.768&+31", ".5", "5&22" DO
BEGIN
OUTTEXT(IF ISNUMERIC(T) THEN "    NUMERIC " ELSE "NOT NUMERIC ");
OUTCHAR('"');
OUTTEXT(T);
OUTCHAR('"');
IF T = "0" THEN OUTCHAR(CHAR(9)); OUTCHAR(CHAR(9));
COMMENT PROBE ;
X := T.GETREAL;
OUTREAL(X, 10, 20);
OUTIMAGE;
END;

OUTIMAGE;

X := 5.&10;
!X := 5&;
!X := 5.;
X := .5;
FOR T :- "", "5.", "5&", "5&+", "5.&", "5.&-", "5.&10" DO
BEGIN
OUTTEXT(IF ISNUMERIC(T) THEN "    NUMERIC " ELSE "NOT NUMERIC ");
OUTCHAR('"');
OUTTEXT(T);
OUTCHAR('"');
OUTIMAGE;
END;

END
Output:
    0.000000000&+000
-3.141500000&+000
2.768000000&+031
5.000000000&+010
5.000000000&-001
5.100000000&+000

NUMERIC "0"             0.000000000&+000
NUMERIC "-3.1415"      -3.141500000&+000
NUMERIC "2.768&+31"     2.768000000&+031
NUMERIC ".5"            5.000000000&-001
NUMERIC "5&22"          5.000000000&+022

NOT NUMERIC ""
NOT NUMERIC "5."
NOT NUMERIC "5&"
NOT NUMERIC "5&+"
NOT NUMERIC "5.&"
NOT NUMERIC "5.&-"
NOT NUMERIC "5.&10"


## Smalltalk

Works with: GNU Smalltalk

The String class has the method isNumeric; this method (at least on version 3.0.4) does not recognize as number strings like '-123'! So I've written an extension...

String extend [
realIsNumeric [
(self first = $+) | (self first =$-)
ifTrue: [
^ (self allButFirst) isNumeric
]
ifFalse: [
^ self isNumeric
]
]
]

{ '1234'.            "true"
'3.14'. '+3.8111'. "true"
'+45'.             "true"
'-3.78'.           "true"
'-3.78.23'. "false"
'123e3'     "false: the notation is not recognized"
} do: [ :a | a realIsNumeric printNl ]

Works with: Smalltalk/X
Works with: GNU Smalltalk

(should work with all)

(Number readFrom:(aString readStream) onError:[nil]) notNil


to handle radix numbers (such as 2r10111), use:

(Scanner scanNumberFrom:(aString readStream)) notNil


## SNOBOL4

This task is easy in Snobol. Use the convert( ) function as a predicate returning success (T) or failure (F) for string to real conversion.

        define('nchk(str)') :(nchk_end)
nchk    convert(str,'real') :s(return)f(freturn)
nchk_end

*       # Wrapper for testing
define('isnum(str)') :(isnum_end)
isnum   isnum = 'F'; isnum = nchk(str) 'T'
isnum = isnum ': ' str :(return)
isnum_end

*       # Test and display
output = isnum('123')
output = isnum('123.0')
output = isnum('123.')
output = isnum('-123')
output = isnum('3.14159')
output = isnum('1.2.3')
output = isnum('abc')
output = isnum('A440')
end
Output:
T: 123
T: 123.0
T: 123.
T: -123
T: 3.14159
F: 1.2.3
F: abc
F: A440

## SQL

Works with: MS SQL version Server 2005
declare @s varchar(10)
set @s = '1234.56'

print isnumeric(@s) --prints 1 if numeric, 0 if not.

if isnumeric(@s)=1 begin print 'Numeric' end
else print 'Non-numeric'


## SQL PL

Works with: Db2 LUW
version 9.7 or higher.

With SQL PL:

--#SET TERMINATOR @

CREATE OR REPLACE FUNCTION IS_NUMERIC (
IN STRING VARCHAR(10)
) RETURNS SMALLINT
-- ) RETURNS BOOLEAN
BEGIN
DECLARE RET SMALLINT;
-- DECLARE RET BOOLEAN;
DECLARE TMP INTEGER;
DECLARE CONTINUE HANDLER FOR SQLSTATE '22018'
SET RET = 1;
-- SET RET = FALSE;

SET RET = 0;
--SET RET = TRUE;
SET TMP = INTEGER(STRING);
RETURN RET;
END @

VALUES IS_NUMERIC('5')@
VALUES IS_NUMERIC('0')@
VALUES IS_NUMERIC('-1')@
VALUES IS_NUMERIC('A')@
VALUES IS_NUMERIC('-')@
VALUES IS_NUMERIC('z')@
VALUES IS_NUMERIC('')@
VALUES IS_NUMERIC(' ')@

Output:

db2 -td@
db2 => BEGIN
...
db2 (cont.) => END @
DB20000I  The SQL command completed successfully.

VALUES IS_NUMERIC('5')

1
------
0

1 record(s) selected.

VALUES IS_NUMERIC('0')

1
------
0

1 record(s) selected.

VALUES IS_NUMERIC('-1')

1
------
0

1 record(s) selected.

VALUES IS_NUMERIC('A')

1
------
1

1 record(s) selected.

VALUES IS_NUMERIC('-')

1
------
1

1 record(s) selected.

VALUES IS_NUMERIC('z')

1
------
1

1 record(s) selected.

VALUES IS_NUMERIC('')

1
------
1

1 record(s) selected.

VALUES IS_NUMERIC(' ')

1
------
1

1 record(s) selected.


## Standard ML

(* this function only recognizes integers in decimal format *)
fun isInteger s = case Int.scan StringCvt.DEC Substring.getc (Substring.full s) of
SOME (_,subs) => Substring.isEmpty subs
| NONE          => false

fun isReal s = case Real.scan Substring.getc (Substring.full s) of
SOME (_,subs) => Substring.isEmpty subs
| NONE          => false

fun isNumeric s = isInteger s orelse isReal s


## Swift

Works with: Swift version 2.x+
func isNumeric(a: String) -> Bool {
return Double(a) != nil
}

Works with: Swift version 1.x

This one only checks whether it is an integer:

func isNumeric(a: String) -> Bool {
return a.toInt() != nil
}


proc isNumeric str {string is double -strict $str}  ## TMG Unix TMG dialect. NOTE: the program also performs some basic normalization (namely, removing the plus sign and translating "E" to "e"): prog: ignore(<< >>) parse(line)\prog parse(error)\prog; line: number *; number: ignore(none) sign float (exp | ={}) = { < True: > 3 2 1 * }; sign: <+>={} | <->={<->} | ={}; float: int ( <.> decim = { 2 <.> 1 } | = { 1 } ) | <.> int = { <.> 1 }; int: smark any(digit) string(digit) scopy; decim: smark string(digit) scopy; exp: any(<<eE>>) sign int = { <e> 2 1 }; error: smark any(nonl) ignore(none) string(nonl) scopy * = { <False: > 1 * }; digit: <<0123456789>>; none: <<>>; nonl: !<< >>; Sample input: 123 +12345.678 .678 1. +1.0E+99 -7. -123e-123 00000 . 1.2.3 0x123 a1-a5 1 000 000 1,000,000 1.00e1e1  Sample output:  True: 123 True: 12345.678 True: .678 True: 1. True: 1.0e99 True: -7. True: -123e-123 True: 00000 False: . False: 1.2.3 False: 0x123 False: a1-a5 False: 1 000 000 False: 1,000,000 False: 1.00e1e1  ## Toka Returns a flag of TRUE if character-string parameter represents a signed or unsigned integer. Otherwise returns a flag of FALSE. The success or failure is dependent on the source is valid in the current numeric base. The >number function also recognizes several optional prefixes for overriding the current base during conversion. [ ( string -- flag ) >number nip ] is isNumeric ( Some tests ) decimal " 100" isNumeric . ( succeeds, 100 is a valid decimal integer ) " 100.21" isNumeric . ( fails, 100.21 is not an integer) " a" isNumeric . ( fails, 'a' is not a valid integer in the decimal base ) "$a" isNumeric .      ( succeeds, because $is a valid override prefix ) ( denoting that the following character is a hexadecimal number ) ## True BASIC Translation of: RapidQ DECLARE FUNCTION isnumeric$

LET true$= "True" LET false$ = "False"
LET s$= "-152.34" PRINT s$, " => "; isnumeric$(s$)
LET s$= "1234.056789" PRINT s$, " => "; isnumeric$(s$)
LET s$= "1234.56" PRINT s$, " => "; isnumeric$(s$)
LET s$= "021101" PRINT s$, " => "; isnumeric$(s$)
LET s$= "Dog" PRINT s$, " => "; isnumeric$(s$)
LET s$= "Bad125" PRINT s$, " => "; isnumeric$(s$)
LET s$= "-0177" PRINT s$, " => "; isnumeric$(s$)
LET s$= "+123abcd.ef" PRINT s$, " => "; isnumeric$(s$)
LET s$= "54321" PRINT s$, " => "; isnumeric$(s$)
LET s$= "123xyz" PRINT s$, " => "; isnumeric$(s$)
LET s$= "xyz" PRINT s$, " => "; isnumeric$(s$)
FUNCTION isnumeric$(s$)
LET optchar$= "" IF len(s$) = 0 then
LET isnumeric$= false$
EXIT FUNCTION
END IF
IF pos(s$,"+") > 1 then LET isnumeric$ = false$EXIT FUNCTION END IF IF pos(s$,"-") > 1 then
LET isnumeric$= false$
EXIT FUNCTION
END IF
LET ndex = 0
FOR i = 1 to len(s$) SELECT CASE ord((s$)[i:i+1-1][1:1])
CASE 43                   !+
CASE 45                   !-
CASE 46                   !.
IF ndex = 1 then
LET isnumeric$= false$
EXIT FUNCTION
END IF
LET ndex = 1
CASE 48 to 57             !0 a 9
CASE else
IF pos(optchar$,((s$)[i:i+1-1])) = 0 then
LET isnumeric$= false$
EXIT FUNCTION
END IF
END SELECT
NEXT i
LET isnumeric$= true$
END FUNCTION
END


## UNIX Shell

#!/bin/bash
isnum() {
printf "%f" $1 >/dev/null 2>&1 } check() { if isnum$1
then
echo "$1 is numeric" else echo "$1 is NOT numeric"
fi
}

check 2
check -3
check +45.44
check -33.332
check 33.aa
check 3.3.3

Output:
2 is numeric
-3 is numeric
+45.44 is numeric
-33.332 is numeric
33.aa is NOT numeric
3.3.3 is NOT numeric


## Ursa

def isnum (string str)
try
double str
return true
catch valueerror
return false
end try
end isnum

## VBA

In France, IsNumeric("123.45") return False. So we have to check the "." or "," and replace it by the Application.DecimalSeparator.

Sub Main()
Debug.Print Is_Numeric("")
Debug.Print Is_Numeric("-5.32")
Debug.Print Is_Numeric("-51,321 32")
Debug.Print Is_Numeric("123.4")
Debug.Print Is_Numeric("123,4")
Debug.Print Is_Numeric("123;4")
Debug.Print Is_Numeric("123.4x")
End Sub

Private Function Is_Numeric(s As String) As Boolean
Dim Separat As String, Other As String
Separat = Application.DecimalSeparator
Other = IIf(Separat = ",", ".", ",")
Is_Numeric = IsNumeric(Replace(s, Other, Separat))
End Function


## VBScript

IsNumeric(Expr)


Returns a True if numeric and a false if not.

## Vedit macro language

This routine returns TRUE if there is numeric value at current cursor location. Only signed and unsigned integers are recognized, in decimal, hex (preceded with 0x) or octal (preceded with 0o). Remove the SUPPRESS option to evaluate an expression instead of single numeric value.

:IS_NUMERIC:
if (Num_Eval(SUPPRESS)==0 && Cur_Char != '0') {
Return(FALSE)
} else {
Return(TRUE)
}

## Visual Basic .NET

Works with: Visual Basic .NET version 2005
Dim Value As String = "+123"

If IsNumeric(Value) Then
PRINT "It is numeric."
End If


## V (Vlang)

import strconv

fn is_numeric(s string) bool {
strconv.atof64(s) or {
return false
}
return true
}

fn main() {
println("Are these strings numeric?")
strings := ["1", "3.14", "-100", "1e2", "NaN", "rose", "0xff", "0b110"]
for s in strings {
println("  ${s:4} ->${is_numeric(s)}")
}
}
Output:
Are these strings numeric?
1 -> true
3.14 -> true
-100 -> true
1e2 -> true
NaN -> false
rose -> false
0xff -> true
0b110 -> true


## Wren

Library: Wren-fmt

Wren's Num class already has a static method which does what this task requires.

import "/fmt" for Fmt

System.print("Are these strings numeric?")

for (s in ["1", "3.14", "-100", "1e2", "NaN", "0xaf", "rose"]) {
var  i = Num.fromString(s) // returns null if 's' is not numeric
System.print("  %(Fmt.s(4, s)) -> %((i != null) ? "yes" : "no")")
}

Output:
Are these strings numeric?
1 -> yes
3.14 -> yes
-100 -> yes
1e2 -> yes
NaN -> yes
0xaf -> yes
rose -> no


## XLISP

The inbuilt function STRING->NUMBER returns the numeric value of a string if it can. We discard this value and return the Boolean value 'true'; otherwise, the IF conditional will not be satisfied and will return 'false'.

(DEFUN NUMERICP (X)
(IF (STRING->NUMBER X) T))

## XPL0

The compiler is more strict in the characters it accepts as numeric than what is accepted here. This program indicates more of what the input intrinsics (IntIn, RlIn and HexIn) would accept as numeric.

string 0;

func IsNumeric(Str);
char Str;
[while Str(0) # 0 do
[if Str(0) >= ^0 and Str(0) <= ^9 then return true;
if Str(0) = ^$then [if Str(1) >= ^0 and Str(1) <= ^9 then return true; if Str(1) >= ^A and Str(1) <= ^F then return true; if Str(1) >= ^a and Str(1) <= ^f then return true; ]; Str:= Str+1; ]; return false; ]; int Strs, S; [Text(0, "Are these strings numeric?^m^j"); Strs:= ["1", "3.14", "-100", "1e2", "NaN", "$af", "%1_1011", "rose", ". 3", "num9", "x$9", "x$ a"];
for S:= 0 to 12-1 do
[Text(0, if IsNumeric(Strs(S)) then "yes : " else "no  : ");
Text(0, Strs(S));
CrLf(0);
];
]
Output:
Are these strings numeric?
yes : 1
yes : 3.14
yes : -100
yes : 1e2
no  : NaN
yes : $af yes : %1_1011 no : rose yes : . 3 yes : num9 yes : x$ 9
no  : x$a  ## Z80 Assembly Works with: CP/M 3.1 version YAZE-AG-2.51.2 Z80 emulator Works with: ZSM4 macro assembler version YAZE-AG-2.51.2 Z80 emulator Use the /S8 switch on the ZSM4 assembler for 8 significant characters for labels and names  ; ; Check if input string is a number using Z80 assembly language ; ; Runs under CP/M 3.1 on YAZE-AG-2.51.2 Z80 emulator ; Assembled with zsm4 on same emulator/OS, uses macro capabilities of said assembler ; Created with vim under Windows ; ; 2023-04-04 Xorph ; ; ; Useful definitions ; bdos equ 05h ; Call to CP/M BDOS function strdel equ 6eh ; Set string delimiter readstr equ 0ah ; Read string from console wrtstr equ 09h ; Write string to console nul equ 00h ; ASCII control characters esc equ 1bh cr equ 0dh lf equ 0ah cnull equ '0' ; ASCII character constants cnine equ '9' cminus equ '-' cdot equ '.' buflen equ 30h ; Length of input buffer minbit equ 00h ; Bit 0 is used as flag for '-' dotbit equ 01h ; Bit 1 is used as flag for '.' ; ; Macros for BDOS calls ; setdel macro char ; Set string delimiter to char ld c,strdel ld e,char call bdos endm print macro msg ; Output string to console ld c,wrtstr ld de,msg call bdos endm newline macro ; Print newline ld c,wrtstr ld de,crlf call bdos endm readln macro buf ; Read a line from input ld c,readstr ld de,buf call bdos endm ; ; ===================== ; Start of main program ; ===================== ; cseg isnum: setdel nul ; Set string terminator to nul ('\0') - '$' is default in CP/M
print	help
newline
newline

ld	b,buflen	; Clear input buffer
ld	hl,bufcont
clrloop:
ld	(hl),0
inc	hl
djnz	clrloop

newline			; Newline is discarded during input, so write one...

ld	a,(inputbuf+1)	; Length of actual input
cp	0		; If empty input, quit
ret	z

ld	b,a		; Loop counter for djnz instruction
ld	c,0		; Use c for flags: '-' and '.' may be encountered at most once, '-' only at start
ld	hl,bufcont	; Start of actual input

loop:
ld	a,(hl)		; Get next character into a

cp	cminus		; Check minus sign
jr	z,chkminus

cp	cdot		; Check dot
jr	z,chkdot

cp	cnull		; Check if below '0'
jr	c,notanum

cp	cnine+1		; Check if above '9'
jr	nc,notanum

checknxt:
set	minbit,c	; Whatever the case, no more '-' are allowed after the first character
inc	hl		; Increase hl to next character and repeat until done
djnz	loop

print	bufcont		; If we made it this far, we are done and the string is numeric
print	yesmsg
newline
newline

done:
jp	readnum		; Read next input from user until terminated with ^C or empty input

notanum:
print	bufcont		; Print failure message
print	nomsg
newline
newline
jr	done

chkminus:
bit	minbit,c	; If a '-' is encountered and the flag is already set, the string is not numeric
jr	nz,notanum
set	minbit,c	; Otherwise, set flag and check next character
jr	checknxt

chkdot:
bit	dotbit,c	; If a '.' is encountered and the flag is already set, the string is not numeric
jr	nz,notanum
set	dotbit,c	; Otherwise, set flag and check next character
jr	checknxt

;
; ===================
; End of main program
; ===================
;

;
; ================
; Data definitions
; ================
;

dseg

help:
defz	'Enter numbers to check, end with empty line or ^C'

inputbuf:			; Input buffer for CP/M BDOS call
defb	buflen		; Maximum possible length
defb	00h		; Returned length of actual input
bufcont:
defs	buflen		; Actual input area
defb	nul		; Null terminator for output, if buffer is filled completely

yesmsg:
defz	' is numeric'
nomsg:
defz	' is not numeric'

crlf:	defb	cr,lf,nul	; Generic newline

Output:
E>isnum
Enter numbers to check, end with empty line or ^C

1234
1234 is numeric

hello
hello is not numeric

12.34
12.34 is numeric

-98.76
-98.76 is numeric

4.6.76
4.6.76 is not numeric

34-56-23
34-56-23 is not numeric

-.9876543210
-.9876543210 is numeric

444555.
444555. is numeric

1234c
1234c is not numeric

123e45
123e45 is not numeric



## zkl

fcn isNum(text){
try{ text.toInt(); True }
catch{ try{ text.toFloat(); True }
catch{ False }
}
}
isNum("123.4")  //-->True
isNum("123")    //-->True
isNum("-123.4") //-->True
isNum("123.4x") //-->False
isNum("hoho")   //-->False
isNum(123.4)    //-->True
isNum(123)      //-->True


## Zoea

program: numeric
case: 1   input: '1'      output: true
case: 2   input: '-3'     output: true
case: 3   input: '22.7'   output: true
case: 4   input: 'a'      output: false
case: 5   input: 'Fred'   output: false
case: 6   input: ''       output: false`