Getting the number of decimal places
Getting the number of decimal places is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
- Task
Write a program (function) to get the number of decimal places in a given number.
- Examples
-
- for num = 12.345 decimals = 3, and
- for num = 12.3450 decimals = 4
(Note that the reference implementation – in the Ring language – shows a function over a given number rather than a given numeric string, and that the sample values shown above are not enclosed in quotes).
11l
F dec(n)
R I ‘.’ C n {n.split(‘.’).last.len} E 0
print(dec(‘12.345’))
print(dec(‘12.3450’))- Output:
3 4
Action!
INCLUDE "D2:REAL.ACT" ;from the Action! Tool Kit
BYTE FUNC FindC(CHAR ARRAY s CHAR c)
BYTE i
FOR i=1 TO s(0)
DO
IF s(i)=c THEN
RETURN (i)
FI
OD
RETURN (0)
BYTE FUNC DecimalCount(REAL POINTER r)
CHAR ARRAY s(20),sub(20)
BYTE i,dotPos,ePos,count
INT exp
StrR(r,s)
ePos=FindC(s,'E)
IF ePos>0 THEN
ePos==+1
IF s(ePos)='+ THEN
ePos==+1
FI
SCopyS(sub,s,ePos,s(0))
exp=ValI(sub)
ELSE
exp=0
FI
dotPos=FindC(s,'.)
count=0
IF dotPos>0 THEN
FOR i=dotPos+1 TO s(0)
DO
IF s(i)<'0 OR s(i)>'9 THEN
EXIT
FI
count==+1
OD
FI
IF exp<0 THEN
count==-exp
ELSEIF exp<count THEN
count==-exp
ELSE
count=0
FI
RETURN (count)
PROC Test(REAL POINTER r)
BYTE count
count=DecimalCount(r)
PrintR(r)
PrintF(" has %I decimals%E",count)
RETURN
PROC Main()
REAL r
Put(125) PutE() ;clear screen
ValR("1234",r) Test(r)
ValR("123.4",r) Test(r)
ValR("12.34",r) Test(r)
ValR("1.234",r) Test(r)
ValR("0.1234",r) Test(r)
ValR("1.234E-3",r) Test(r)
ValR("1.234E-10",r) Test(r)
ValR("1.E-10",r) Test(r)
ValR("1.23456789E10",r) Test(r)
RETURN- Output:
Screenshot from Atari 8-bit computer
1234 has 0 decimals 123.4 has 1 decimals 12.34 has 2 decimals 1.234 has 3 decimals .1234 has 4 decimals 1.234E-03 has 6 decimals 1.234E-10 has 13 decimals 1E-10 has 10 decimals 1.23456789E+10 has 0 decimals
Ada
-- Report the number of decimal places in a number
-- J. Carter 2023 Apr
-- I presume the input is a String containing the image of the value; the test values of 12.345 & 12.3450 represent the same number,
-- and so would give the same result otherwise
with Ada.Strings.Fixed;
with Ada.Text_IO;
procedure Decimal_Places is
function Num_Places (Number : in String) return Natural;
-- Returns the number of decimal places in the numeric image in Number
function Num_Places (Number : in String) return Natural is
Dot : constant Natural := Ada.Strings.Fixed.Index (Number, ".");
begin -- Num_Places
if Dot = 0 then
return 0;
end if;
return Number'Last - Dot;
end Num_Places;
Test_1 : constant String := "12.345";
Test_2 : constant String := "12.3450";
begin -- Decimal_Places
Ada.Text_IO.Put_Line (Item => Test_1 & (1 .. 10 - Test_1'Length => ' ') & Num_Places (Test_1)'Image);
Ada.Text_IO.Put_Line (Item => Test_2 & (1 .. 10 - Test_2'Length => ' ') & Num_Places (Test_2)'Image);
end Decimal_Places;
- Output:
12.345 3 12.3450 4
Arturo
nofDecimals: function [n][
str: (string? n)? -> n -> to :string n
size last split.by:"." str
]
loop [12 12.345 "12.3450" 12.34567] 'n ->
print ["number of decimals of" n "->" nofDecimals n]
- Output:
number of decimals of 12 -> 2 number of decimals of 12.345 -> 3 number of decimals of 12.3450 -> 4 number of decimals of 12.34567 -> 5
AutoHotkey
for i, v in [10, "10", 12.345, "12.345", 12.3450, "12.3450"]
output .= v " has " StrLen(StrSplit(v, ".").2) " decimals.`n"
MsgBox % output
- Output:
10 has 0 decimals. 10 has 0 decimals. 12.345 has 3 decimals. 12.345 has 3 decimals. 12.3450 has 4 decimals. 12.3450 has 4 decimals.
AWK
# syntax: GAWK -f GETTING_THE_NUMBER_OF_DECIMALS.AWK
BEGIN {
n = split("10,1.,1.0,12.345,12.3450",arr,",")
for (i=1; i<=n; i++) {
s = arr[i]
x = index(s,".")
printf("%s has %d decimals\n",s,x?length(s)-x:x)
}
exit(0)
}
- Output:
10 has 0 decimals 1. has 0 decimals 1.0 has 1 decimals 12.345 has 3 decimals 12.3450 has 4 decimals
BASIC
BASIC256
arraybase 1
dim n[5]
n[1] = 7
n[2] = 12.00
n[3] = 12.345
n[4] = 12.345677
n[5] = 0.142857142857142
for i = n[?,] to n[?]
print n[i] + " has " + dec(n[i]) + " decimals"
next i
end
function dec(n)
c = string(n)
if instr(c, ".") then return length(mid(c, instr(c, ".") + 1, length(c))) else return 0
end function
- Output:
7 has 0 decimals 12.0 has 1 decimals 12.345 has 3 decimals 12.345677 has 6 decimals 0.14285714286 has 11 decimals
Chipmunk Basic
100 dim n(4)
110 data 7,12,12.345,12.345677,0.142857
120 for i = 0 to 4
130 read n(i)
140 print n(i);" has ";dek(n(i));" decimals"
150 next i
160 end
170 sub dek(n)
180 c$ = str$(n)
190 if instr(c$,".") then dek = len(mid$(c$,instr(c$,".")+1)) else dek = 0
200 end sub
FreeBASIC
Function dec(n As Double) As Uinteger
Dim As String c = Str(n)
Return Iif(Instr(c, "."), Len(Mid(c,Instr(c, ".")+1)), 0)
End Function
Dim As Double n(1 To ...) => {7, 12.00, 12.345, 12.345677, 0.142857142857142}
For i As Integer = 1 To Ubound(n)
Print n(i); " has "; dec(n(i)); " decimals"
Next i
Sleep
- Output:
7 has 0 decimals 12 has 0 decimals 12.345 has 3 decimals 12.345677 has 6 decimals 0.142857142857142 has 15 decimals
GW-BASIC
The MSX Basic solution works without any changes.
MSX Basic
100 DIM N(4)
110 DATA 7,12,12.345,12.345677,0.142857
120 FOR I = 0 TO 4
130 READ N(I)
140 GOSUB 180
150 PRINT N(I);"has";DEC;"decimals"
160 NEXT I
170 END
180 'sub dec(n)
190 C$ = STR$(N(I))
200 IF INSTR(C$,".") <> 0 THEN DEC = LEN(MID$(C$,INSTR(C$,".")+1)) ELSE DEC = 0
210 RETURN
- Output:
7 has 0 decimals 12 has 0 decimals 12.345 has 3 decimals 12.34568 has 5 decimals .142857 has 6 decimals
QBasic
DECLARE FUNCTION dec! (n!)
DIM n(4)
DATA 7,12.00,12.345,12.345677,0.142857142857142
FOR i = LBOUND(n) TO UBOUND(n)
READ n(i)
PRINT n(i); "has"; dec(n(i)); "decimals"
NEXT i
END
FUNCTION dec (n)
c$ = STR$(n)
IF INSTR(c$, ".") THEN dec = LEN(MID$(c$, INSTR(c$, ".") + 1)) ELSE dec = 0
END FUNCTION
QB64
Dim n(4)
Data 7,12.00,12.345,12.345677,0.142857142857142
For i = LBound(n) To UBound(n)
Read n(i)
Print n(i); "has"; dec(n(i)); "decimals"
Next i
End
Function dec (n)
c$ = Str$(n)
If InStr(c$, ".") Then dec = Len(Mid$(c$, InStr(c$, ".") + 1)) Else dec = 0
End Function
Run BASIC
dim n(4)
n(0) = 7
n(1) = 12.00
n(2) = 12.345
n(3) = 12.345677
n(4) = 0.142857142857142
for i = 0 to 4
print n(i); " has "; dek(n(i)); " decimals"
next i
end
function dek(n)
c$ = str$(n)
if instr(c$, ".") then dek = len(mid$(c$, instr(c$, ".") + 1)) else dek = 0
end function
True BASIC
FUNCTION dec(n_t)
LET c$ = STR$(n_t)
IF POS(c$,".")<>0 THEN LET dec = LEN((c$)[POS(c$,".")+1:maxnum]) ELSE LET dec = 0
END FUNCTION
DIM n(5)
DATA 7, 12.00, 12.345, 12.345677, 0.142857142857142
FOR i = LBOUND(n) TO UBOUND(n)
READ n(i)
PRINT n(i); "has"; dec(n(i)); "decimals"
NEXT i
END
- Output:
Same as QBasic entry.
Yabasic
dim n(4)
data 7,12.00,12.345,12.345677,0.142857142857142
for i = 0 to 4
read n(i)
print n(i), " has ", dek(n(i)), " decimals"
next i
end
sub dek(n)
c$ = str$(n)
if instr(c$, ".") then return len(mid$(c$, instr(c$, ".") + 1)) else return 0: fi
end sub
- Output:
7 has 0 decimals 12 has 0 decimals 12.345 has 3 decimals 12.3457 has 4 decimals 0.142857 has 6 decimals
C
#include <stdio.h>
#include <string.h>
int findNumOfDec(const char *s) {
int pos = 0;
while (s[pos] && s[pos++] != '.') {}
return strlen(s + pos);
}
void test(const char *s) {
int num = findNumOfDec(s);
const char *p = num != 1 ? "s" : "";
printf("%s has %d decimal%s\n", s, num, p);
}
int main() {
test("12");
test("12.0");
test("12.345");
test("12.345555555555");
test("12.3450");
test("12.34555555555555555555");
char str[64];
sprintf(str, "%f", 1.2345e+54);
test(str);
return 0;
}
- Output:
12 has 0 decimals 12.0 has 1 decimal 12.345 has 3 decimals 12.345555555555 has 12 decimals 12.3450 has 4 decimals 12.34555555555555555555 has 20 decimals 1234500000000000060751116919315055127939946206157864960.000000 has 6 decimals
C++
#include <iostream>
#include <cstring>
int findNumOfDec(const char *s) {
int pos = 0;
while (s[pos] && s[pos++] != '.') {}
return strlen(s + pos);
}
void test(const char *s) {
int num = findNumOfDec(s);
const char *p = num != 1 ? "s" : "";
std::cout << s << " has " << num << " decimal" << p << "\n";
}
int main() {
test("12");
test("12.0");
test("12.345");
test("12.345555555555");
test("12.3450");
test("12.34555555555555555555");
char str[64];
sprintf(str, "%f", 1.2345e+54);
test(str);
return 0;
}
- Output:
12 has 0 decimals 12.0 has 1 decimal 12.345 has 3 decimals 12.345555555555 has 12 decimals 12.3450 has 4 decimals 12.34555555555555555555 has 20 decimals 1234500000000000060751116919315055127939946206157864960.000000 has 6 decimals
EasyLang
func ndec n .
while abs (n - floor (n + 1e-15)) > 1e-15
n *= 10
r += 1
.
return r
.
for i in [ 0.00000000000001 12.345 12.3450 1.1 0.1234567 ]
write ndec i & " "
.
- Output:
14 3 3 1 7
FutureBasic
local fn CountDecimalPlaces( numberStr as CFStringRef ) as NSInteger
CFRange range = fn StringRangeOfString( numberStr, @"." )
if ( range.location != NSNotFound )
return len(numberStr) - range.location - 1
else
return 0
end if
end fn = 0
CFStringRef numberStr
numberStr = @"12"
printf @"%@ has %d decimals", numberStr, fn CountDecimalPlaces( numberStr )
numberStr = @"12.345"
printf @"%@ has %d decimals", numberStr, fn CountDecimalPlaces( numberStr )
numberStr = @"12.345555555555"
printf @"%@ has %d decimals", numberStr, fn CountDecimalPlaces( numberStr )
numberStr = @"12.3450"
printf @"%@ has %d decimals", numberStr, fn CountDecimalPlaces( numberStr )
numberStr = @"12.34555555555555555555"
printf @"%@ has %d decimals", numberStr, fn CountDecimalPlaces( numberStr )
HandleEvents- Output:
12 has 0 decimals 12.345 has 3 decimals 12.345555555555 has 12 decimals 12.3450 has 4 decimals 12.34555555555555555555 has 20 decimals
F#
//Getting the number of decimal places. Nigel Galloway: March 23rd., 2023.
let fN g=let n,g=Seq.length g,g|>Seq.tryFindIndex((=)'.') in match g with Some g->n-g-1 |_->0
["12";"12.00";"12.345";"12.3450";"12.34500"]|>List.iter(fN>>printfn "%d")
- Output:
0 2 3 4 5
Go
package main
import (
"fmt"
"log"
"math"
"strings"
)
var error = "Argument must be a numeric literal or a decimal numeric string."
func getNumDecimals(n interface{}) int {
switch v := n.(type) {
case int:
return 0
case float64:
if v == math.Trunc(v) {
return 0
}
s := fmt.Sprintf("%g", v)
return len(strings.Split(s, ".")[1])
case string:
if v == "" {
log.Fatal(error)
}
if v[0] == '+' || v[0] == '-' {
v = v[1:]
}
for _, c := range v {
if strings.IndexRune("0123456789.", c) == -1 {
log.Fatal(error)
}
}
s := strings.Split(v, ".")
ls := len(s)
if ls == 1 {
return 0
} else if ls == 2 {
return len(s[1])
} else {
log.Fatal("Too many decimal points")
}
default:
log.Fatal(error)
}
return 0
}
func main() {
var a = []interface{}{12, 12.345, 12.345555555555, "12.3450", "12.34555555555555555555", 12.345e53}
for _, n := range a {
d := getNumDecimals(n)
switch v := n.(type) {
case string:
fmt.Printf("%q has %d decimals\n", v, d)
case float32, float64:
fmt.Printf("%g has %d decimals\n", v, d)
default:
fmt.Printf("%d has %d decimals\n", v, d)
}
}
}
- Output:
12 has 0 decimals 12.345 has 3 decimals 12.345555555555 has 12 decimals "12.3450" has 4 decimals "12.34555555555555555555" has 20 decimals 1.2345e+54 has 0 decimals
Haskell
decimal :: String -> Int
decimal [] = 0
decimal ('.':xs) = length xs
decimal (_:xs) = decimal xs
numDecimal :: Double -> Int
numDecimal = decimal . show
main = print . map numDecimal $ [12.0, 12.345, 12.3450, 12.345555555555, 12.34555555555555555555, 1.2345e+54]
- Output:
[1,3,3,12,15,7]
Java
int decimalPlaces(double value) {
String string = String.valueOf(value);
return string.length() - (string.indexOf('.') + 1);
}
Or
public static int findNumOfDec(double x){
String str = String.valueOf(x);
if(str.endsWith(".0")) return 0;
else return (str.substring(str.indexOf('.')).length() - 1);
}
jq
The current (March 2023) official releases of jq, gojq, fq, and jaq cannot be relied upon to preserve the literal form of numbers, and in particular they drop the final 0 of `12.3450` when presented as a number. However, the current "master" version of jq retains the literal form of numbers. Accordingly, both the numeric and the string forms of 12.3450 are included in the suite of test cases, and two sets of results are presented below.
def number_decimal_digits:
. as $in
| def nil: . == null or . == "";
def nodecimal: # e.g. 12 or 12e-2
capture("^[-+]?[0-9]*([eE](?<sign>[-+]?)(?<p>[0-9]+))?$")
| if .sign|nil then 0
elif .p|nil then "internal error: \($in)"|error
else .p|tonumber
end;
tostring
| nodecimal
// capture("^[-+]?[0-9]*[.](?<d>[0-9]+)([eE](?<sign>[-+]?)(?<p>[0-9]+))?$") # has decimal
// null
| if type == "number" then .
elif not then 0
elif .d|nil then 0
elif (.sign|nil) and .p == null then .d|length
elif (.sign|nil) or .sign == "+" then [0, (.d|length) - (.p|tonumber)] | max
elif .sign == "-" then (.d|length) + (.p|tonumber)
else "internal error: \($in)"|error
end ;
def examples:
[12.345, 3],
[12.3450, 4],
["12.3450", 4],
[1e-2, 2],
[1.23e2, 0];
def task:
examples
| (first|number_decimal_digits) as $d
| if $d == last then empty
else "\(first) has \(last) decimal places but the computed value is \($d)"
end;
task, "Bye."- Output:
Using gojq:
12.345 has 4 decimal places but the computed value is 3 Bye.
Using jq post-1.6:
Bye.
Julia
function postprecision(str::String)
s = lowercase(str)
if 'e' in s
s, ex = split(s, "e")
expdig = parse(Int, ex)
else
expdig = 0
end
dig = something(findfirst('.', reverse(s)), 1) - 1 - expdig
return dig > 0 ? dig : 0
end
postprecision(x::Integer) = 0
postprecision(x::Real, max=22) = postprecision(string(round(Float64(x), digits=max)))
testnums = ["0.00100", 0.00100, 001.805, 1.0 / 3, 2//3, 12, 12.345, "12.3450",
"12.34555555555555555555", 1.2345e+54, 1.2345e-08, "1.2345e-08", π]
for n in testnums
println("$n has $(postprecision(n)) decimals.")
end
- Output:
0.00100 has 5 decimals. 0.001 has 3 decimals. 1.805 has 3 decimals. 0.3333333333333333 has 16 decimals. 2//3 has 16 decimals. 12 has 0 decimals. 12.345 has 3 decimals. 12.3450 has 4 decimals. 12.34555555555555555555 has 20 decimals. 1.2345e54 has 0 decimals. 1.2345e-8 has 12 decimals. 1.2345e-08 has 12 decimals. π has 15 decimals.
Kotlin
fun findNumOfDec(x: Double): Int {
val str = x.toString()
if (str.endsWith(".0")) {
return 0
}
return str.substring(str.indexOf('.')).length - 1
}
fun main() {
for (n in listOf(12.0, 12.345, 12.345555555555, 12.3450, 12.34555555555555555555, 1.2345e+54)) {
println("%f has %d decimals".format(n, findNumOfDec(n)))
}
}
- Output:
12.000000 has 0 decimals 12.345000 has 3 decimals 12.345556 has 12 decimals 12.345000 has 3 decimals 12.345556 has 15 decimals 1234500000000000000000000000000000000000000000000000000.000000 has 7 decimals
Lambdatalk
In lambdatalk numbers are words/strings, some operators, like "+,-,*,/,...", know what to do with words like "123".
A first answer could be
{W.length
{S.rest
{S.replace \. by space in 12.3450}}}
-> 4
This is a better one, if considering that ending zeroes should not be considered as decimals
{def decimals
{def decimals.r
{lambda {:w}
{if {= {W.first :w} 0}
then {decimals.r {W.rest :w}}
else :w}}}
{lambda {:w}
{W.length
{decimals.r
{S.first
{W.reverse
{S.replace \. by space in :w}}}}}}}
-> decimals
{decimals 12.34560001230000}
-> 10Numbers can be of any size.
Mathematica /Wolfram Language
ClearAll[DecimalDigits]
DecimalDigits[r_String] := Module[{pos},
If[StringContainsQ[r, "."],
pos = StringPosition[r, "."][[-1, 1]];
StringLength[StringDrop[r, pos]]
,
0
]
]
DecimalDigits["12.345"]
DecimalDigits["12.3450"]
DecimalDigits["8"]
DecimalDigits["3128"]
DecimalDigits["13."]
DecimalDigits["13.1312312"]
- Output:
3 4 0 0 0 7
Perl
Need pragma bignum to handle decimals beyond 15 digits.
use bignum;
printf "Fractional precision: %2s Number: %s\n", length((split /\./, $_)[1]) // 0, $_
for 9, 12.345, <12.3450>, 0.1234567890987654321, 1/3, 1.5**63;
- Output:
Fractional precision: 0 Number: 9 Fractional precision: 3 Number: 12.345 Fractional precision: 4 Number: 12.3450 Fractional precision: 19 Number: 0.1234567890987654321 Fractional precision: 40 Number: 0.3333333333333333333333333333333333333333 Fractional precision: 63 Number: 124093581919.648947697827373650380188008224280338254175148904323577880859375
Phix
constant fracfmt = iff(machine_bits()=32?"%.14g":"%.18g")
function num_decimals(object o)
integer nd = -1
string s, t
if integer(o) then
nd = 0
s = sprintf("%d",o)
elsif atom(o) then
s = sprintf("%.19g",o)
o -= trunc(o)
if o=0 then
nd = 0
else
t = sprintf(fracfmt,o)
end if
elsif string(o) then
s = o
t = s
else
crash("unknown type")
end if
if nd=-1 then
integer e = find('e',t)
if e then
{t,e} = {t[1..e-1],to_number(t[e+1..$])}
end if
integer dot = find('.',t)
nd = iff(dot?max(length(t)-dot-e,0):max(-e,0))
end if
s = shorten(s,"digits",5)
return {s,nd}
end function
sequence tests = {"0.00100", 0.00100, 001.805, 1/3, 12, 12.345, 12.345555555555,
"12.3450", "12.34555555555555555555", 12.345e53, 1.2345e-08,
"12.345e53", "1.2345e-08", "0.1234567890987654321",
"124093581919.648947697827373650380188008224280338254175148904323577880859375"}
for i=1 to length(tests) do
printf(1,"%25s has %d decimals\n",num_decimals(tests[i]))
end for
- Output:
32 bit
0.00100 has 5 decimals
0.001 has 3 decimals
1.805 has 3 decimals
0.3333333333333333 has 14 decimals
12 has 0 decimals
12.345 has 3 decimals
12.345555555555 has 12 decimals
12.3450 has 4 decimals
12.34555555555555555555 has 20 decimals
1.2345e+54 has 0 decimals
1.2345e-8 has 12 decimals
12.345e53 has 0 decimals
1.2345e-08 has 12 decimals
0.1234567890987654321 has 19 decimals
12409...59375 (76 digits) has 63 decimals
64 bit as above except
0.3333333333333333333 has 18 decimals
Python
Treated as a function over a string representation of a number to allow the capturing of significant trailing zeros.
In [6]: def dec(n):
...: return len(n.rsplit('.')[-1]) if '.' in n else 0
In [7]: dec('12.345')
Out[7]: 3
In [8]: dec('12.3450')
Out[8]: 4
In [9]:
Or, defining a slightly less partial function, over a given number, rather than a string:
'''Report the decimal counts in default stringifications.'''
import math
# decimalCount :: Num -> Either String (Int, Int)
def decimalCount(n):
'''Either a message string, or a tuple
giving the number of decimals in the default
(repr) representations of the real
(and any imaginary part) of the given number.
'''
# decimalLen :: Float -> Int
def decimalLen(f):
return len(repr(f).split('.')[-1])
return Right(
(0, 0) if isinstance(n, int) else (
(decimalLen(n), 0)
) if isinstance(n, float) else (
tuple(decimalLen(x) for x in [n.real, n.imag])
)
) if isinstance(n, (float, complex, int)) else (
Left(repr(n) + ' is not a float, complex or int')
)
# -------------------------- TEST --------------------------
# main :: IO ()
def main():
'''Counts of decimals in default stringifications of
real (and any imaginary) components of various
Python numeric values.
'''
print(fTable(
'Decimal counts in stringifications of real and imaginary components:'
)(repr)(
either(identity)(repr)
)(decimalCount)([
7, 1.25, 1.23456e2,
1 / 7,
2 ** 0.5,
math.pi, math.e,
complex(1.23, 4.567),
None
]))
# ------------------------ GENERIC -------------------------
# Left :: a -> Either a b
def Left(x):
'''Constructor for an empty Either (option type) value
with an associated string.
'''
return {'type': 'Either', 'Right': None, 'Left': x}
# Right :: b -> Either a b
def Right(x):
'''Constructor for a populated Either (option type) value'''
return {'type': 'Either', 'Left': None, 'Right': x}
# either :: (a -> c) -> (b -> c) -> Either a b -> c
def either(fl):
'''The application of fl to e if e is a Left value,
or the application of fr to e if e is a Right value.
'''
return lambda fr: lambda e: fl(e['Left']) if (
None is e['Right']
) else fr(e['Right'])
# identity :: a -> a
def identity(x):
'''The identity function.'''
return x
# ------------------------ DISPLAY -------------------------
# fTable :: String -> (a -> String) ->
# (b -> String) -> (a -> b) -> [a] -> String
def fTable(s):
'''Heading -> x display function -> fx display function ->
f -> xs -> tabular string.
'''
def gox(xShow):
def gofx(fxShow):
def gof(f):
def goxs(xs):
ys = [xShow(x) for x in xs]
w = max(map(len, ys))
def arrowed(x, y):
return y.rjust(w, ' ') + ' -> ' + fxShow(f(x))
return s + '\n' + '\n'.join(
map(arrowed, xs, ys)
)
return goxs
return gof
return gofx
return gox
# MAIN ---
if __name__ == '__main__':
main()
- Output:
Decimal counts in stringifications of real and imaginary components:
7 -> (0, 0)
1.25 -> (2, 0)
123.456 -> (3, 0)
0.14285714285714285 -> (17, 0)
1.4142135623730951 -> (16, 0)
3.141592653589793 -> (15, 0)
2.718281828459045 -> (15, 0)
(1.23+4.567j) -> (2, 3)
None -> None is not a float, complex or int
Raku
Raku does not specifically have a "decimal" number type, however we can easily determine the fractional precision of a rational number. It is somewhat touchy-feely for floating point numbers; (what is the fractional precision for 2.45e-12?), it's pretty pointless for Integers; (zero, aalllways zero...), but Rats (rationals) are doable. Note that these are (mostly) actual numerics, not numeric strings. The exception is '12.3450'. That is a numeric string since actual numerics automatically truncate non-significant trailing zeros. If you want to retain them, you need to pass the value as a string. (As below.)
use Rat::Precise;
printf "Fractional precision: %-2s || Number: %s\n", (.split('.')[1] // '').chars, $_
for 9, 12.345, '12.3450', 0.1234567890987654321, (1.5**63).precise;
- Output:
Fractional precision: 0 || Number: 9 Fractional precision: 3 || Number: 12.345 Fractional precision: 4 || Number: 12.3450 Fractional precision: 19 || Number: 0.1234567890987654321 Fractional precision: 63 || Number: 124093581919.648947697827373650380188008224280338254175148904323577880859375
REXX
Since the REXX language stores numbers as strings, the issue of trailing zeros is a moot point.
If the number (as specified) has trailing zeros, there are left intact.
I took it to mean that the number of decimal digits past the decimal point are to be counted and displayed.
Any number specified in exponential notation is first converted to a whole or fractional integer (or an integer with scale),
and that number is then examined.
/*REXX pgm counts number of decimal digits which are to the right of the decimal point. */
numeric digits 1000 /*ensure enuf dec digs for calculations*/
@.=; /*initialize a stemmed array to nulls. */
parse arg @.1; if @.1='' then do; #= 9 /*#: is the number of default numbers.*/
@.1 = 12
@.2 = 12.345
@.3 = 12.345555555555
@.4 = 12.3450
@.5 = 12.34555555555555555555
@.6 = 1.2345e+54
@.7 = 1.2345e-54
@.8 = 0.1234567890987654321
@.9 = 1.5 ** 63 /*calculate 1.5 raised to 63rd power.*/
end
else #= 1 /*the # of numbers specified on the CL.*/
say 'fractional'
say ' decimals ' center("number", 75)
say '══════════' copies("═", 75)
do j=1 for #; n= countDec(@.j) /*obtain the number of fractional digs.*/
say right(n, 5) left('',4) @.j /*show # of fract. digits & original #.*/
end /*j*/
exit 0 /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
countDec: procedure; parse upper arg x /*obtain a number from the invoker. */
if pos('E', x)>0 then do /*handle if the number has an exponent.*/
LX= length(x) /*length of the original number*/
parse var x 'E' expon /*obtain the exponent. */
LE= length(LE) /*the length of the exponent. */
numeric digits LX + LE /*ensure enough decimal digits.*/
x= format(x, , , 0) /*REXX does the heavy lifting. */
end
parse var x '.' fract /*parse number, get the fractional part*/
return length(fract) /*return number of fractional digits. */
- output when using the default inputs:
fractional
decimals number
══════════ ═══════════════════════════════════════════════════════════════════════════
0 12
3 12.345
12 12.345555555555
4 12.3450
20 12.34555555555555555555
0 1.2345E+54
58 1.2345E-54
19 0.1234567890987654321
63 124093581919.648947697827373650380188008224280338254175148904323577880859375
Ring
# Testing the function
decimals(2) # Unsensitive to the default setting of decimals
n = 5.1945
? NbrOfDecimals(n) # Gives 4
func NbrOfDecimals(n)
nTemp = 1
nNbrOfDecimals = 0
while True
if nNbrOfDecimals < 9
nNbrOfDecimals++
nTemp *= 10
nTemp1 = n * nTemp - ceil( n * nTemp )
if nTemp1 = 0
return nNbrOfDecimals
ok
else
raise("Acceeding the maximum number of 9 decimals!")
ok
end- Output:
4
Another version
decimals(4)
num = 5.1945
strnum = string(num)
pos = substr(strnum,".")
dec = len(strnum) - pos
see "Number of decimals: " + dec + nl- Output:
Number of decimals: 4
RPL
≪ DUP MANT →STR SIZE SWAP XPON - 2 - 0 MAX
≫ 'NDEC' STO
≪ { 12 120 12.345 12.345677 1.23E-20 1.23E20 } → cases
≪ { } 1 cases SIZE FOR j
cases j GET NDEC + NEXT
≫ ≫ 'TASK' STO
- Output:
1: { 0 0 3 6 22 0 }
Sidef
func number_of_decimals(n, limit = 1e5) {
var prec = Num(Num!PREC)>>2
var prev = ''
n = Number(n) if !n.kind_of(Number)
loop {
var str = n.as_dec(prec)
if (prev == str) {
return (str.contains('.') ? str.substr(str.index('.')+1).len : 0)
}
prev = str
prec *= 2
return Inf if (prec > limit)
}
}
var list = [
9, 12.345, "12.3450", "12.345e53",
12.34555555555555555555, 0.1234567890987654321,
Num.pi, 1/3, 1.5**63
]
list.each {|n|
var c = number_of_decimals(n)
say "Number of decimals: #{'%3s' % c} Number: #{n}"
}
- Output:
Number of decimals: 0 Number: 9 Number of decimals: 3 Number: 12.345 Number of decimals: 3 Number: 12.3450 Number of decimals: 0 Number: 12.345e53 Number of decimals: 20 Number: 12.34555555555555555555 Number of decimals: 19 Number: 0.1234567890987654321 Number of decimals: 188 Number: 3.14159265358979323846264338327950288419716939938 Number of decimals: Inf Number: 0.333333333333333333333333333333333333333333333333 Number of decimals: 63 Number: 124093581919.6489476978273736503801880082242803382541751489
Wren
In the following script, the fourth and fifth examples need to be expressed as strings to avoid getting the wrong answer. If we use numbers instead, trailing zeros will be automatically removed and the result will be rounded to 14 significant figures when stringified or printed.
Converting the fourth example to a Rat or BigRat object wouldn't help as the constructor for those classes automatically reduces the numerator and denominator to their lowest terms. BigRat would work for the fifth example but the argument would have to be passed as a string anyway so we might as well just parse the string.
var error = "Argument must be a number or a decimal numeric string."
var getNumDecimals = Fn.new { |n|
if (n is Num) {
if (n.isInteger) return 0
n = n.toString
} else if (n is String) {
if (n == "") Fiber.abort(error)
if (n[0] == "+" || n[0] == "-") n = n[1..-1]
if (!n.all { |c| "0123456789.".contains(c) }) Fiber.abort(error)
} else {
Fiber.abort(error)
}
var s = n.split(".")
var c = s.count
return (c == 1) ? 0 : (c == 2) ? s[1].count : Fiber.abort("Too many decimal points.")
}
var a = [12, 12.345, 12.345555555555, "12.3450", "12.34555555555555555555", 12.345e53]
for (n in a) {
var d = getNumDecimals.call(n)
var ns = (n is String) ? "\"%(n)\"" : "%(n)"
System.print("%(ns) has %(d) decimals")
}
- Output:
12 has 0 decimals 12.345 has 3 decimals 12.345555555555 has 12 decimals "12.3450" has 4 decimals "12.34555555555555555555" has 20 decimals 1.2345e+54 has 0 decimals
XPL0
include xpllib; \for StrLen, Print and FtoA
func FindNumOfDec(S);
char S;
int Pos;
[Pos:= 0;
while S(Pos) & S(Pos)#^. do Pos:= Pos+1;
if S(Pos) = 0 then return 0;
return StrLen(S+Pos+1);
];
proc Test(S);
char S;
int Num, P;
[Num:= FindNumOfDec(S);
P:= if Num # 1 then "s" else "";
Print("%s has %d decimal%s\n", S, Num, P);
];
char Str(64);
[Test("12");
Test("12.0");
Test("12.345");
Test("12.345555555555");
Test("12.3450");
Test("12.34555555555555555555");
FtoA(1.2345e+54, Str);
Test(Str);
]- Output:
12 has 0 decimals 12.0 has 1 decimal 12.345 has 3 decimals 12.345555555555 has 12 decimals 12.3450 has 4 decimals 12.34555555555555555555 has 20 decimals 1234500000000000000000000000000000000000000000000000000.00000 has 5 decimals