I'm working on modernizing Rosetta Code's infrastructure. Starting with communications. Please accept this time-limited open invite to RC's Slack.. --Michael Mol (talk) 20:59, 30 May 2020 (UTC)

ISBN13 check digit

From Rosetta Code
Task
ISBN13 check digit
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Validate the check digit of an ISBN-13 code:

  •   Multiply every other digit by  3.
  •   Add the digits together.
  •   Take the remainder of division by  10.
  •   If it is  0,   the ISBN-13 check digit is correct.


Use the following codes for testing:

  •   978-1734314502       (good)
  •   978-1734314509         (bad)
  •   978-1788399081       (good)
  •   978-1788399083         (bad)


Show output here, on this page


See also



11l[edit]

Translation of: Python
F is_isbn13(=n)
n = n.replace(‘-’, ‘’).replace(‘ ’, ‘’)
I n.len != 13
R 0B
V product = sum(n[(0..).step(2)].map(ch -> Int(ch)))
+ sum(n[(1..).step(2)].map(ch -> Int(ch) * 3))
R product % 10 == 0
 
V tests = |‘978-1734314502
978-1734314509
978-1788399081
978-1788399083’.split("\n")
 
L(t) tests
print(‘ISBN13 ’t‘ validates ’is_isbn13(t))
Output:
ISBN13 978-1734314502 validates 1B
ISBN13 978-1734314509 validates 0B
ISBN13 978-1788399081 validates 1B
ISBN13 978-1788399083 validates 0B

8080 Assembly[edit]

	org	100h
jmp demo
;;; ---------------------------------------------------------------
;;; Check if the string at BC is a valid ISBN-13 code.
;;; Carry set if true, clear if not.
isbn13: lxi h,0 ; HL = accumulator
mov d,h ; D = 0 (such that if E=A, DE=A).
call isbngc ; Get first character
rnc ; Carry clear = invalid
dad d ; Add to running total once
call isbngc ; Get second character
rnc ; Carry clear = invalid
dad d ; Add to running total thrice
dad d
dad d
call isbngc ; Get third character
rnc ; Carry clear = invalid
dad d ; Add to running total once
ldax b ; Fourth character should be a dash '-'
inx b
cpi '-'
stc ; Clear carry w/o touching other flags
cmc
rnz ; If not equal, invalid.
push h ; Keep loop counter on stack
mvi l,5 ; 5 times 2 characters
isbnlp: xthl ; Accumulator in HL
call isbngc ; Get even character
jnc isbnex ; If invalid, stop
dad d ; Add to running total thrice
dad d
dad d
call isbngc ; Get odd character
jnc isbnex ; If invalid, stop
dad d ; Add to running total once
xthl ; Loop counter in (H)L
dcr l ; Done yet?
jnz isbnlp ; If not, do next two characters
pop h ; Get accumulator
lxi d,-10 ; Trial division by ten
isbndv: dad d ; Subtract 10
jc isbndv ; Until zero passed
mov a,l ; Move low byte to A
adi 10 ; Add ten back (the mod loop went one step too far)
rz ; If zero, return (carry will have been set)
ana a ; Otherwise, make sure carry is clear
ret ; And then return
isbnex: pop h ; Test failed - throw away accumulator and return
ret
isbngc: ldax b ; Get character from [BC]
inx b ; Increment BC
sui '0' ; Subtract ASCII '0' to get digit value
cpi 10 ; If 10 or higher (unsigned), invalid digit.
mov e,a ; Set (D)E = value
ret
;;; ---------------------------------------------------------------
;;; Demo: see if the CP/M command line contains a valid ISBN13
;;; code.
demo: lxi b,82h ; Start of command line argument, skipping first space
call isbn13 ; Is it valid?
mvi c,9 ; CP/M print string
lxi d,good ; If carry is set, then yes
jc 5
lxi d,bad ; Otherwise, no.
jmp 5
good: db 'good$'
bad: db 'bad$'
Output:
A>isbn13 978-1734314502
good
A>isbn13 978-1734314509
bad
A>isbn13 978-1788399081
good
A>isbn13 978-1788399083
bad

8086 Assembly[edit]

	cpu	8086
bits 16
org 100h
section .text
jmp demo
isbn13: ;;; ---------------------------------------------------------------
;;; Check if the string at DS:SI is a valid ISBN-13 code.
;;; Carry set if true, clear if false.
xor dx,dx ; DX = running total
xor ah,ah ; Set AH=0 so that AX=AL
call .digit ; Get first digit and add to DX
call .digit ; Get second digit and add to DX
add dx,ax ; Add to DX twice more
add dx,ax
call .digit ; Get third digit and add to DX
lodsb ; Fourth character should be a '-'
cmp al,'-'
jne .fail ; If not equal, fail
mov cx,5 ; Then loop 5 times for the next 10 digits
.loop: call .digit ; Get even digit and add to DX
add dx,ax ; Add to running total twice more
add dx,ax
call .digit ; Get odd digit and add to DX
loop .loop ; Do this 5 times
mov ax,dx ; Divide running total by 10
mov dl,10
div dl
test ah,ah ; Is the remainder zero?
jnz .out ; If not, stop (TEST clears carry)
stc ; Otherwise, set carry and return
ret
.digit: lodsb ; Get first character
sub al,'0' ; Subtract ASCII 0 to get digit value
cmp al,9
ja .dfail
add dx,ax ; Add to ASCII
ret
.dfail: pop dx ; Remove return pointer for .digit from stack
.fail: clc ; Failure - clear carry
.out: ret
;;; ---------------------------------------------------------------
;;; Demo: see if the MS-DOS command line contains a valid ISBN13
;;; code.
demo: mov si,82h ; Start of command line argument skipping space
call isbn13 ; Is it valid?
mov ah,9 ; MS-DOS print string
mov dx,good ; If carry is set, it is good
jc .print
mov dx,bad ; Otherwise, it is bad
.print: int 21h
ret
section .data
good: db 'good$'
bad: db 'bad$'
Output:
C:\>isbn13 978-1734314502
good
C:\>isbn13 978-1734314509
bad
C:\>isbn13 978-1788399081
good
C:\>isbn13 978-1788399083
bad

Ada[edit]

with Ada.Text_IO;
 
procedure ISBN_Check is
 
function Is_Valid (ISBN : String) return Boolean is
Odd  : Boolean := True;
Sum  : Integer := 0;
Value  : Integer;
begin
for I in ISBN'Range loop
if ISBN (I) in '0' .. '9' then
Value := Character'Pos (ISBN (I)) - Character'Pos ('0');
if Odd then
Sum := Sum + Value;
else
Sum := Sum + 3 * Value;
end if;
Odd := not Odd;
end if;
end loop;
return Sum mod 10 = 0;
end Is_Valid;
 
procedure Show (ISBN : String) is
use Ada.Text_IO;
Valid : constant Boolean := Is_Valid (ISBN);
begin
Put (ISBN); Put (" ");
Put ((if Valid then "Good" else "Bad"));
New_Line;
end Show;
begin
Show ("978-1734314502");
Show ("978-1734314509");
Show ("978-1788399081");
Show ("978-1788399083");
end ISBN_Check;
Output:
978-1734314502  Good
978-1734314509  Bad
978-1788399081  Good
978-1788399083  Bad

ALGOL 68[edit]

Works with: ALGOL 68G version Any - tested with release 2.8.3.win32
BEGIN # Check some IsBN13 check digits                                         #
# returns TRUE if the alledged isbn13 has the correct check sum, #
# FALSE otherwise #
# non-digit characters are ignored and there must be 13 digits #
PROC check isbn13 = ( STRING isbn13 )BOOL:
BEGIN
INT sum := 0;
INT digits := 0;
BOOL other digit := FALSE;
FOR pos FROM LWB isbn13 TO UPB isbn13 DO
IF CHAR c = isbn13[ pos ];
c >= "0" AND c <= "9"
THEN
# have another digit #
digits +:= 1;
sum +:= ( ABS c - ABS "0" ) * IF other digit THEN 3 ELSE 1 FI;
other digit := NOT other digit
FI
OD;
digits = 13 AND sum MOD 10 = 0
END; # check isbn13 #
# task test cases #
[]STRING tests = ( "978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083" );
[]BOOL expected = ( TRUE, FALSE, TRUE, FALSE );
FOR pos FROM LWB tests TO UPB tests DO
BOOL result = check isbn13( tests[ pos ] );
print( ( tests[ pos ]
, ": "
, IF result THEN "good" ELSE "bad" FI
, IF result = expected[ pos ] THEN "" ELSE " NOT AS EXPECTED" FI
, newline
)
)
OD
END
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

APL[edit]

Works with: Dyalog APL
check_isbn13←{
13≠⍴n←(⍵∊⎕D)/⍵:0
0=10|(⍎¨n)+.×13⍴1 3
}
Output:
      check_isbn13¨ '978-1734314502' '978-1734314509' '978-1788399081' '978-1788399083'
1 0 1 0

AppleScript[edit]

Composition of pure functions[edit]

-------------------- ISBN13 CHECK DIGIT --------------------
 
-- isISBN13 :: String -> Bool
on isISBN13(s)
script digitValue
on |λ|(c)
if isDigit(c) then
{c as integer}
else
{}
end if
end |λ|
end script
 
set digits to concatMap(digitValue, characters of s)
 
13 = length of digits ¬
and 0 = sum(zipWith(my mul, digits, cycle({1, 3}))) mod 10
end isISBN13
 
 
--------------------------- TEST ---------------------------
on run
script test
on |λ|(s)
{s, isISBN13(s)}
end |λ|
end script
 
map(test, {"978-1734314502", "978-1734314509", ¬
"978-1788399081", "978-1788399083"})
end run
 
 
-------------------- GENERIC FUNCTIONS ---------------------
 
-- concatMap :: (a -> [b]) -> [a] -> [b]
on concatMap(f, xs)
set lng to length of xs
set acc to {}
tell mReturn(f)
repeat with i from 1 to lng
set acc to acc & (|λ|(item i of xs, i, xs))
end repeat
end tell
return acc
end concatMap
 
 
-- cycle :: [a] -> Generator [a]
on cycle(xs)
script
property lng : 1 + (length of xs)
property i : missing value
on |λ|()
if missing value is i then
set i to 1
else
set nxt to (1 + i) mod lng
if 0 = ((1 + i) mod lng) then
set i to 1
else
set i to nxt
end if
end if
return item i of xs
end |λ|
end script
end cycle
 
 
-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
tell mReturn(f)
set v to startValue
set lng to length of xs
repeat with i from 1 to lng
set v to |λ|(v, item i of xs, i, xs)
end repeat
return v
end tell
end foldl
 
 
-- isDigit :: Char -> Bool
on isDigit(c)
set n to (id of c)
48 ≤ n and 57 ≥ n
end isDigit
 
 
-- length :: [a] -> Int
on |length|(xs)
set c to class of xs
if list is c or string is c then
length of xs
else
(2 ^ 29 - 1) -- (maxInt - simple proxy for non-finite)
end if
end |length|
 
 
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
-- The list obtained by applying f
-- to each element of 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 |λ|(item i of xs, i, xs)
end repeat
return lst
end tell
end map
 
 
-- min :: Ord a => a -> a -> a
on min(x, y)
if y < x then
y
else
x
end if
end min
 
 
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
-- 2nd class handler function lifted into 1st class script wrapper.
if script is class of f then
f
else
script
property |λ| : f
end script
end if
end mReturn
 
 
-- mul (*) :: Num a => a -> a -> a
on mul(a, b)
a * b
end mul
 
 
-- sum :: [Num] -> Num
on sum(xs)
script add
on |λ|(a, b)
a + b
end |λ|
end script
 
foldl(add, 0, xs)
end sum
 
 
-- take :: Int -> [a] -> [a]
-- take :: Int -> String -> String
on take(n, xs)
set c to class of xs
if list is c then
if 0 < n then
items 1 thru min(n, length of xs) of xs
else
{}
end if
else if string is c then
if 0 < n then
text 1 thru min(n, length of xs) of xs
else
""
end if
else if script is c then
set ys to {}
repeat with i from 1 to n
set v to |λ|() of xs
if missing value is v then
return ys
else
set end of ys to v
end if
end repeat
return ys
else
missing value
end if
end take
 
 
-- zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
on zipWith(f, xs, ys)
set lng to min(|length|(xs), |length|(ys))
if 1 > lng then return {}
set xs_ to take(lng, xs) -- Allow for non-finite
set ys_ to take(lng, ys) -- generators like cycle etc
set lst to {}
tell mReturn(f)
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs_, item i of ys_)
end repeat
return lst
end tell
end zipWith
Output:
{{"978-1734314502", true}, {"978-1734314509", false}, {"978-1788399081", true}, {"978-1788399083", false}}

Straightforward[edit]

This task can be tackled very simply by working through the numeric text two characters at a time:

on validateISBN13(ISBN13)
if (ISBN13's class is not text) then return false
 
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to {"-", space}
set ISBN13 to ISBN13's text items
set AppleScript's text item delimiters to ""
set ISBN13 to ISBN13 as text
set AppleScript's text item delimiters to astid
 
if (((count ISBN13) is not 13) or (ISBN13 contains ".") or (ISBN13 contains ",")) then return false
try
ISBN13 as number
on error
return false
end try
 
set sum to 0
repeat with i from 1 to 12 by 2
set sum to sum + (character i of ISBN13) + (character (i + 1) of ISBN13) * 3 -- Automatic text-to-number coercions.
end repeat
 
return ((sum + (character 13 of ISBN13)) mod 10 = 0)
end validateISBN13
 
-- Test:
set output to {}
set verdicts to {"bad", "good"}
repeat with thisISBN13 in {"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"}
set isValid to validateISBN13(thisISBN13)
set end of output to thisISBN13 & ": " & item ((isValid as integer) + 1) of verdicts
end repeat
 
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to linefeed
set output to output as text
set AppleScript's text item delimiters to astid
return output
Output:
"978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad"

Or it can be handled purely numerically. Since the "weights" alternate and are palindromic, it makes no difference whether the last digit or the first is treated as the check digit. In fact, if preferred, the repeat below can go round 7 times with the return line as simply: return (sum mod 10 = 0).

on validateISBN13(ISBN13)
if (ISBN13's class is not text) then return false
 
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to {"-", space}
set ISBN13 to ISBN13's text items
set AppleScript's text item delimiters to ""
set ISBN13 to ISBN13 as text
set AppleScript's text item delimiters to astid
 
if (((count ISBN13) is not 13) or (ISBN13 contains ".") or (ISBN13 contains ",")) then return false
try
set ISBN13 to ISBN13 as number
on error
return false
end try
 
set sum to 0
repeat 6 times
set sum to sum + ISBN13 mod 10 + ISBN13 mod 100 div 10 * 3
set ISBN13 to ISBN13 div 100
end repeat
 
return ((sum + ISBN13) mod 10 = 0)
end validateISBN13

Arturo[edit]

validISBN?: function [isbn][
currentCheck: to :integer to :string last isbn
isbn: map split chop replace isbn "-" "" => [to :integer]
 
s: 0
loop.with:'i isbn 'n [
if? even? i -> s: s + n
else -> s: s + 3*n
]
checkDigit: 10 - s % 10
return currentCheck = checkDigit
]
 
tests: [
"978-1734314502" "978-1734314509"
"978-1788399081" "978-1788399083"
]
 
loop tests 'test [
print [test "=>" validISBN? test]
]
Output:
978-1734314502 => true 
978-1734314509 => false 
978-1788399081 => true 
978-1788399083 => false

AutoHotkey[edit]

ISBN13_check_digit(n){
for i, v in StrSplit(RegExReplace(n, "[^0-9]"))
sum += !Mod(i, 2) ? v*3 : v
return n "`t" (Mod(sum, 10) ? "(bad)" : "(good)")
}
Examples:
output := ""
nums := ["978-1734314502","978-1734314509","978-1788399081","978-1788399083"]
for i, n in nums
output .= ISBN13_check_digit(n) "`n"
MsgBox % output
return
Output:
978-1734314502	(good)
978-1734314509	(bad)
978-1788399081	(good)
978-1788399083	(bad)

AWK[edit]

 
# syntax: GAWK -f ISBN13_CHECK_DIGIT.AWK
BEGIN {
arr[++n] = "978-1734314502"
arr[++n] = "978-1734314509"
arr[++n] = "978-1788399081"
arr[++n] = "978-1788399083"
arr[++n] = "9780820424521"
arr[++n] = "0820424528"
for (i=1; i<=n; i++) {
printf("%s %s\n",arr[i],isbn13(arr[i]))
}
exit(0)
}
function isbn13(isbn, check_digit,i,sum) {
gsub(/[ -]/,"",isbn)
if (length(isbn) != 13) { return("NG length") }
for (i=1; i<=12; i++) {
sum += substr(isbn,i,1) * (i % 2 == 1 ? 1 : 3)
}
check_digit = 10 - (sum % 10)
return(substr(isbn,13,1) == check_digit ? "OK" : sprintf("NG check digit S/B %d",check_digit))
}
 
Output:
978-1734314502 OK
978-1734314509 NG check digit S/B 2
978-1788399081 OK
978-1788399083 NG check digit S/B 1
9780820424521 OK
0820424528 NG length

C[edit]

#include <stdio.h>
 
int check_isbn13(const char *isbn) {
int ch = *isbn, count = 0, sum = 0;
/* check isbn contains 13 digits and calculate weighted sum */
for ( ; ch != 0; ch = *++isbn, ++count) {
/* skip hyphens or spaces */
if (ch == ' ' || ch == '-') {
--count;
continue;
}
if (ch < '0' || ch > '9') {
return 0;
}
if (count & 1) {
sum += 3 * (ch - '0');
} else {
sum += ch - '0';
}
}
if (count != 13) return 0;
return !(sum%10);
}
 
int main() {
int i;
const char* isbns[] = {"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"};
for (i = 0; i < 4; ++i) {
printf("%s: %s\n", isbns[i], check_isbn13(isbns[i]) ? "good" : "bad");
}
return 0;
}
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

C++[edit]

Translation of: C
#include <iostream>
 
bool check_isbn13(std::string isbn) {
int count = 0;
int sum = 0;
 
for (auto ch : isbn) {
/* skip hyphens or spaces */
if (ch == ' ' || ch == '-') {
continue;
}
if (ch < '0' || ch > '9') {
return false;
}
if (count & 1) {
sum += 3 * (ch - '0');
} else {
sum += ch - '0';
}
count++;
}
 
if (count != 13) {
return false;
}
return sum % 10 == 0;
}
 
int main() {
auto isbns = { "978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083" };
for (auto isbn : isbns) {
std::cout << isbn << ": " << (check_isbn13(isbn) ? "good" : "bad") << '\n';
}
 
return 0;
}
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

C#[edit]

using System;
using System.Linq;
 
public class Program
{
public static void Main() {
Console.WriteLine(CheckISBN13("978-1734314502"));
Console.WriteLine(CheckISBN13("978-1734314509"));
Console.WriteLine(CheckISBN13("978-1788399081"));
Console.WriteLine(CheckISBN13("978-1788399083"));
 
static bool CheckISBN13(string code) {
code = code.Replace("-", "").Replace(" ", "");
if (code.Length != 13) return false;
int sum = 0;
foreach (var (index, digit) in code.Select((digit, index) => (index, digit))) {
if (char.IsDigit(digit)) sum += (digit - '0') * (index % 2 == 0 ? 1 : 3);
else return false;
}
return sum % 10 == 0;
}
}
}
Output:
True
False
True
False

COBOL[edit]

Works with: GnuCOBOL
      ******************************************************************
* Author: Jay Moseley
* Date: November 10, 2019
* Purpose: Testing various subprograms/ functions.
* Tectonics: cobc -xj testSubs.cbl
******************************************************************
IDENTIFICATION DIVISION.
 
PROGRAM-ID. testSubs.
ENVIRONMENT DIVISION.
 
CONFIGURATION SECTION.
REPOSITORY.
FUNCTION ALL INTRINSIC
FUNCTION validISBN13.
 
INPUT-OUTPUT SECTION.
FILE-CONTROL.
 
DATA DIVISION.
 
FILE SECTION.
 
WORKING-STORAGE SECTION.
 
01 IX PIC S9(4) COMP.
01 TEST-ISBNS.
02 FILLER PIC X(14) VALUE '978-1734314502'.
02 FILLER PIC X(14) VALUE '978-1734314509'.
02 FILLER PIC X(14) VALUE '978-1788399081'.
02 FILLER PIC X(14) VALUE '978-1788399083'.
01 TEST-ISBN REDEFINES TEST-ISBNS
OCCURS 4 TIMES
PIC X(14).
 
PROCEDURE DIVISION.
 
MAIN-PROCEDURE.
 
PERFORM
VARYING IX
FROM 1
BY 1
UNTIL IX > 4
 
DISPLAY TEST-ISBN (IX) ' ' WITH NO ADVANCING
END-DISPLAY
IF validISBN13(TEST-ISBN (IX)) = -1
DISPLAY '(bad)'
ELSE
DISPLAY '(good)'
END-IF
 
END-PERFORM.
 
GOBACK.
 
END PROGRAM testSubs.
 
******************************************************************
* Author: Jay Moseley
* Date: May 19, 2016
* Purpose: validate ISBN-13 (International Standard
* Book Number).
******************************************************************
IDENTIFICATION DIVISION.
 
FUNCTION-ID. validISBN13.
ENVIRONMENT DIVISION.
 
CONFIGURATION SECTION.
REPOSITORY.
FUNCTION ALL INTRINSIC.
 
INPUT-OUTPUT SECTION.
FILE-CONTROL.
 
DATA DIVISION.
 
FILE SECTION.
 
WORKING-STORAGE SECTION.
 
01 PASSED-SIZE PIC S9(6) COMP-5.
01 IX PIC S9(4) COMP.
 
01 WORK-FIELDS.
02 WF-DIGIT PIC X.
02 WF-COUNT PIC 9(2).
88 WEIGHT-1 VALUE 1, 3, 5, 7, 9, 11, 13.
88 WEIGHT-3 VALUE 2, 4, 6, 8, 10, 12.
02 WF-SUM PIC S9(8) COMP.
 
LINKAGE SECTION.
 
01 PASSED-ISBN PIC X ANY LENGTH.
01 RETURN-VALUE PIC S9.
 
PROCEDURE DIVISION USING PASSED-ISBN
RETURNING RETURN-VALUE.
 
CALL 'C$PARAMSIZE'
USING 1
GIVING PASSED-SIZE
END-CALL.
 
COMPUTE-CKDIGIT.
 
INITIALIZE WORK-FIELDS.
PERFORM
VARYING IX
FROM 1
BY 1
UNTIL IX GREATER THAN PASSED-SIZE
 
MOVE PASSED-ISBN (IX:1) TO WF-DIGIT
IF WF-DIGIT IS NUMERIC
ADD 1 TO WF-COUNT
IF WEIGHT-1
ADD NUMVAL(WF-DIGIT) TO WF-SUM
ELSE
COMPUTE WF-SUM = WF-SUM +
(NUMVAL(WF-DIGIT) * 3)
END-COMPUTE
END-IF
END-IF
 
END-PERFORM.
 
IF MOD(WF-SUM, 10) = 0
MOVE +0 TO RETURN-VALUE
ELSE
MOVE -1 TO RETURN-VALUE
END-IF.
 
GOBACK.
* - - - - - - - - - - - - - - - - - - - - - - PROGRAM EXIT POINT
 
END FUNCTION validISBN13.
 
Output:
978-1734314502   (good)
978-1734314509   (bad)
978-1788399081   (good)
978-1788399083   (bad)

Cowgol[edit]

include "cowgol.coh";

sub check_isbn13(isbn: [uint8]): (r: uint8) is

   var n: uint8 := 0;
   r := 0;
   loop    
       var c := [isbn];
       isbn := @next isbn;
       if c == 0 then break; end if;
       c := c - '0';
       if c <= 9 then
           r := r + c;
           n := n + 1;
           if (n & 1) == 0 then
               r := r + c * 2;
           end if;
       end if;
   end loop;
   if n == 13 and r%10 == 0 then
       r := 1;
   else
       r := 0;
   end if;

end sub;

var isbns: [uint8][] := {

   "978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"

};

var result: [uint8][] := {": bad\n", ": good\n"};

var n: uint8 := 0; while n < @sizeof isbns loop

   print(isbns[n]);
   print(result[check_isbn13(isbns[n])]);
   n := n + 1;

end loop;

978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

D[edit]

Translation of: Kotlin
import std.stdio;
 
bool isValidISBN13(string text) {
int sum, i;
foreach (c; text) {
if ('0' <= c && c <= '9') {
int value = c - '0';
if (i % 2 == 0) {
sum += value;
} else {
sum += 3 * value;
}
 
i++;
}
}
return i == 13 && 0 == sum % 10;
}
 
unittest {
assert(isValidISBN13("978-1734314502"));
assert(!isValidISBN13("978-1734314509"));
assert(isValidISBN13("978-1788399081"));
assert(!isValidISBN13("978-1788399083"));
}

Excel[edit]

LAMBDA[edit]

Binding the name ISBN13Check to the following lambda expression in the Name Manager of the Excel WorkBook:

(See LAMBDA: The ultimate Excel worksheet function)

ISBN13Check
=LAMBDA(s,
LET(
ns, FILTERP(
LAMBDA(v,
NOT(ISERROR(v))
)
)(
VALUE(CHARSROW(s))
),
ixs, SEQUENCE(
1, COLUMNS(ns),
1, 1
),
 
0 = MOD(
SUM(
IF(0 <> MOD(ixs, 2),
INDEX(ns, ixs),
3 * INDEX(ns, ixs)
)
),
10
)
)
)

and also assuming the following generic bindings in the Name Manager for the WorkBook:

CHARSROW
=LAMBDA(s,
MID(s,
SEQUENCE(1, LEN(s), 1, 1),
1
)
)
 
 
FILTERP
=LAMBDA(p,
LAMBDA(xs,
FILTER(xs, p(xs))
)
)
 
 
ISDIGIT
=LAMBDA(c,
LET(
ic, CODE(c),
 
AND(47 < ic, 58 > ic)
)
)
Output:
fx =ISBN13Check(A2)
A B
1 Candidate string ISBN13 checked
2 978-1734314502 TRUE
3 978-1734314509 FALSE
4 978-1788399081 TRUE
5 978-1788399083 FALSE


Factor[edit]

USING: combinators.short-circuit formatting kernel math
math.functions math.parser math.vectors qw sequences
sequences.extras sets unicode ;
 
: (isbn13?) ( str -- ? )
string>digits
[ <evens> sum ] [ <odds> 3 v*n sum + ] bi 10 divisor? ;
 
: isbn13? ( str -- ? )
"- " without
{ [ length 13 = ] [ [ digit? ] all? ] [ (isbn13?) ] } 1&& ;
 
qw{ 978-1734314502 978-1734314509 978-1788399081 978-1788399083 }
[ dup isbn13? "good" "bad" ? "%s: %s\n" printf ] each
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Fortran[edit]

 
program isbn13
implicit none
 
character(len=14), dimension(4), parameter :: isbns=["978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"]
integer :: i
 
do i = 1, ubound(isbns, 1)
if (check_isbn13(isbns(i))) then
print*, isbns(i), " : ", "good"
else
print*, isbns(i), " : ", "bad"
end if
end do
contains
pure function check_isbn13(isbn)
character(len=*), intent(in) :: isbn
logical :: check_isbn13
integer :: summ, counter, i, digit
 
check_isbn13 = .false.
counter = 0
summ = 0
 
do i = 1, len(isbn)
if (isbn(i:i) == ' ' .or. isbn(i:i) == '-') cycle
counter = counter + 1
read(isbn(i:i), '(I1)') digit
if (modulo(counter, 2) == 0) then
summ = summ + 3*digit
else
summ = summ + digit
end if
end do
if (counter == 13 .and. modulo(summ, 10) == 0) check_isbn13 = .true.
end function check_isbn13
end program isbn13
 
Output:
 978-1734314502 : good
 978-1734314509 : bad
 978-1788399081 : good
 978-1788399083 : bad

FreeBASIC[edit]

#define ZEROC asc("0")
 
function is_num( byval c as string ) as boolean
if asc(c) >= ZEROC andalso asc(c)<ZEROC+10 then return true
return false
end function
 
function is_good_isbn( isbn as string ) as boolean
dim as uinteger charno = 0, digitno = 0, sum = 0
dim as string*1 currchar
while charno <= len(isbn)
currchar = mid(isbn,charno,1)
if is_num(currchar) then
if digitno mod 2 = 1 then
sum += 2*(asc(currchar)-ZEROC)
end if
sum += asc(currchar)-ZEROC
digitno += 1
end if
charno += 1
wend
if sum mod 10 = 0 then
return true
else
return false
end if
end function
 
dim as string isbns(0 to 3) = { "978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083" }
dim as uinteger i
for i = 0 to 3
if is_good_isbn( isbns(i) ) then
print isbns(i)+": good"
else
print isbns(i)+": bad"
end if
next i
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Fōrmulæ[edit]

Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.

Programs in Fōrmulæ are created/edited online in its website, However they run on execution servers. By default remote servers are used, but they are limited in memory and processing power, since they are intended for demonstration and casual use. A local server can be downloaded and installed, it has no limitations (it runs in your own computer). Because of that, example programs can be fully visualized and edited, but some of them will not run if they require a moderate or heavy computation/memory resources, and no local server is being used.

In this page you can see the program(s) related to this task and their results.

Go[edit]

package main
 
import (
"fmt"
"strings"
"unicode/utf8"
)
 
func checkIsbn13(isbn string) bool {
// remove any hyphens or spaces
isbn = strings.ReplaceAll(strings.ReplaceAll(isbn, "-", ""), " ", "")
// check length == 13
le := utf8.RuneCountInString(isbn)
if le != 13 {
return false
}
// check only contains digits and calculate weighted sum
sum := int32(0)
for i, c := range isbn {
if c < '0' || c > '9' {
return false
}
if i%2 == 0 {
sum += c - '0'
} else {
sum += 3 * (c - '0')
}
}
return sum%10 == 0
}
 
func main() {
isbns := []string{"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"}
for _, isbn := range isbns {
res := "bad"
if checkIsbn13(isbn) {
res = "good"
}
fmt.Printf("%s: %s\n", isbn, res)
}
}
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Haskell[edit]

import Data.Char (digitToInt, isDigit)
import Text.Printf (printf)
 
pair :: Num a => [a] -> [(a, a)]
pair [] = []
pair xs = p (take 2 xs) : pair (drop 2 xs)
where
p ps = case ps of
(x : y : zs) -> (x, y)
(x : zs) -> (x, 0)
 
validIsbn13 :: String -> Bool
validIsbn13 isbn
| length (digits isbn) /= 13 = False
| otherwise = calc isbn `rem` 10 == 0
where
digits = map digitToInt . filter isDigit
calc = sum . map (\(x, y) -> x + y * 3) . pair . digits
 
main :: IO ()
main =
mapM_
(printf "%s: Valid: %s\n" <*> (show . validIsbn13))
[ "978-1734314502",
"978-1734314509",
"978-1788399081",
"978-1788399083"
]
Output:
978-1734314502: Valid: True
978-1734314509: Valid: False
978-1788399081: Valid: True
978-1788399083: Valid: False

Or, expressed in terms of cycle:

import Data.Char (digitToInt, isDigit)
 
isISBN13 :: String -> Bool
isISBN13 =
(0 ==)
. flip rem 10
. sum
. flip
(zipWith ((*) . digitToInt) . filter isDigit)
(cycle [1, 3])
 
main :: IO ()
main =
mapM_
(print . ((,) <*> isISBN13))
[ "978-1734314502",
"978-1734314509",
"978-1788399081",
"978-1788399083"
]
Output:
("978-1734314502",True)
("978-1734314509",False)
("978-1788399081",True)
("978-1788399083",False)

IS-BASIC[edit]

100 PROGRAM "ISBN13.bas"
110 DO
120 PRINT :INPUT PROMPT "ISBN-13 code: ":IS$
130 IF IS$="" THEN EXIT DO
140 IF ISBN(IS$) THEN
150 PRINT "Ok."
160 ELSE
170 PRINT "CRC error."
180 END IF
190 LOOP
200 DEF TRIM$(S$)
210 LET T$=""
220 FOR I=1 TO LEN(S$)
230 IF S$(I)>CHR$(47) AND S$(I)<CHR$(58) THEN LET T$=T$&S$(I)
240 NEXT
250 LET TRIM$=T$
260 END DEF
270 DEF ISBN(S$)
280 LET SUM,ISBN=0:LET ISBN$=TRIM$(IS$)
290 IF LEN(ISBN$)<>13 THEN PRINT "Invalid length.":EXIT DEF
300 FOR I=1 TO 11 STEP 2
310 LET SUM=SUM+VAL(ISBN$(I))+VAL(ISBN$(I+1))*3
320 NEXT
330 LET SUM=SUM+VAL(ISBN$(13))
340 IF MOD(SUM,10)=0 THEN LET ISBN=-1
350 END DEF

J[edit]

   D            =:  '0123456789'
 
isbn13c =: D&([ [email protected]:i. clean)
check =: 0 = 10 | lc
lc =: [ +/@:* weight
weight =: 1 3 $~ #
clean =: ] -. a. -. [
Output:
   isbn13c;._1 ' 978-1734314502 978-1734314509 978-1788399081 978-1788399083'
1 0 1 0

Java[edit]

public static void main(){
System.out.println(isISBN13("978-1734314502"));
System.out.println(isISBN13("978-1734314509"));
System.out.println(isISBN13("978-1788399081"));
System.out.println(isISBN13("978-1788399083"));
}
public static boolean isISBN13(String in){
int pre = Integer.parseInt(in.substring(0,3));
if (pre!=978)return false;
String postStr = in.substring(4);
if (postStr.length()!=10)return false;
int post = Integer.parseInt(postStr);
int sum = 38;
for(int x = 0; x<10;x+=2)
sum += (postStr.charAt(x)-48)*3 + ((postStr.charAt(x+1)-48));
if(sum%10==0) return true;
return false;
}
 
Output:
true
false
true
false

Julia[edit]

function isbncheck(str)
return sum(iseven(i) ? 3 * parse(Int, ch) : parse(Int, ch)
for (i, ch) in enumerate(replace(str, r"\D" => ""))) % 10 == 0
end
 
const testingcodes = ["978-1734314502", "978-1734314509",
"978-1788399081", "978-1788399083"]
 
for code in testingcodes
println(code, ": ", isbncheck(code) ? "good" : "bad")
end
 
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Kotlin[edit]

 
fun isValidISBN13(text: String): Boolean {
val isbn = text.replace(Regex("[- ]"), "")
return isbn.length == 13 && isbn.map { it - '0' }
.mapIndexed { index, value -> when (index % 2) { 0 -> value else -> 3 * value } }
.sum() % 10 == 0
}
 

Tested using Spek

 
describe("ISBN Utilities") {
mapOf(
"978-1734314502" to true,
"978-1734314509" to false,
"978-1788399081" to true,
"978-1788399083" to false
).forEach { (input, expected) ->
it("returns $expected for $input") {
println("$input: ${when(isValidISBN13(input)) {
true -> "good"
else -> "bad"
}}")
assert(isValidISBN13(input) == expected)
}
}
}
 
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

langur[edit]

Works with: langur version 0.8.11

In this example, we map to multiple functions (actually 1 no-op).

val .isbn13checkdigit = f(var .s) {
.s = replace(.s, RE/[\- ]/)
matching(re/^[0-9]{13}$/, .s) and
fold(f{+}, map [_, f{x 3}], s2n .s) div 10
}
 
val .tests = h{
"978-1734314502": true,
"978-1734314509": false,
"978-1788399081": true,
"978-1788399083": false,
}
 
for .key of .tests {
val .pass = .isbn13checkdigit(.key)
write .key, ": ", if(.pass: "good"; "bad")
writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")
}
Works with: langur version 0.9.0

In this example, we set a for loop value as it progresses.

val .isbn13checkdigit = f(var .s) {
.s = replace(.s, RE/[\- ]/)
var .alt = true
matching(re/^[0-9]{13}$/, .s) and
for[=0] .d in s2n(.s) { _for += if(not= .alt: .d x 3; .d) } div 10
}
 
val .tests = h{
"978-1734314502": true,
"978-1734314509": false,
"978-1788399081": true,
"978-1788399083": false,
}
 
for .key of .tests {
val .pass = .isbn13checkdigit(.key)
write .key, ": ", if(.pass: "good"; "bad")
writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")
}
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Lua[edit]

Translation of: C
function checkIsbn13(isbn)
local count = 0
local sum = 0
for c in isbn:gmatch"." do
if c == ' ' or c == '-' then
-- skip
elseif c < '0' or '9' < c then
return false
else
local digit = c - '0'
if (count % 2) > 0 then
sum = sum + 3 * digit
else
sum = sum + digit
end
count = count + 1
end
end
 
if count ~= 13 then
return false
end
return (sum % 10) == 0
end
 
function test(isbn)
if checkIsbn13(isbn) then
print(isbn .. ": good")
else
print(isbn .. ": bad")
end
end
 
function main()
test("978-1734314502")
test("978-1734314509")
test("978-1788399081")
test("978-1788399083")
end
 
main()
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad


Mathematica / Wolfram Language[edit]

ClearAll[ValidISBNQ]
ValidISBNQ[iban_String] := Module[{i},
i = StringReplace[iban, {" " -> "", "-" -> ""}];
If[StringMatchQ[i, Repeated[DigitCharacter]],
i = ToExpression /@ Characters[i];
i[[2 ;; ;; 2]] *= 3;
Mod[Total[i], 10] == 0
,
False
]
]
ValidISBNQ["978-1734314502"]
ValidISBNQ["978-1734314509"]
ValidISBNQ["978-1788399081"]
ValidISBNQ["978-1788399083"]
Output:
True
False
True
False


Nanoquery[edit]

Translation of: Go
def checkIsbn13(isbn)
// remove any hyphens or spaces
isbn = str(isbn).replace("-","").replace(" ","")
 
// check length = 13
if len(isbn) != 13
return false
end
 
// check only contains digits and calculate weighted sum
sum = 0
for i in range(0, len(isbn) - 1)
c = isbn[i]
if (ord(c) < ord("0")) or (ord(c) > ord("9"))
return false
end
 
if (i % 2) = 0
sum += ord(c) - ord("0")
else
sum += 3 * (ord(c) - ord("0"))
end
end
 
return (sum % 10) = 0
end
 
isbns = {"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"}
for isbn in isbns
res = "bad"
if checkIsbn13(isbn)
res = "good"
end
 
print format("%s: %s\n", isbn, res)
end
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Nim[edit]

import strutils, strformat
 
func is_isbn*(s: string): bool =
var sum, len: int
for c in s:
if is_digit(c):
sum += (ord(c) - ord('0')) * (if len mod 2 == 0: 1 else: 3)
len += 1
elif c != ' ' and c != '-':
return false
return (len == 13) and (sum mod 10 == 0)
 
when is_main_module:
let isbns = [ "978-1734314502", "978-1734314509",
"978-1788399081", "978-1788399083" ]
for isbn in isbns:
var quality: string = if is_isbn(isbn): "good" else: "bad"
echo &"{isbn}: {quality}"
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Perl[edit]

use strict;
use warnings;
use feature 'say';
 
sub check_digit {
my($isbn) = @_; my($sum);
$sum += (1,3)[$_%2] * (split '', join '', split /\D/, $isbn)[$_] for 0..11;
(10 - $sum % 10) % 10;
}
 
for (<978-1734314502 978-1734314509 978-1788399081 978-1788399083 978-2-74839-908-0 978-2-74839-908-5>) {
my($isbn,$check) = /(.*)(.)/;
my $check_d = check_digit($isbn);
say "$_ : " . ($check == $check_d ? 'Good' : "Bad check-digit $check; should be $check_d")
}
Output:
978-1734314502 : Good
978-1734314509 : Bad check-digit 9; should be 2
978-1788399081 : Good
978-1788399083 : Bad check-digit 3; should be 1
978-2-74839-908-0 : Good
978-2-74839-908-5 : Bad check-digit 5; should be 0

Phix[edit]

procedure check_isbn13(string isbn)
integer digits = 0, checksum = 0, w = 1
for i=1 to length(isbn) do
integer ch = isbn[i]
if ch!=' ' and ch!='-' then
ch -= '0'
if ch<0 or ch>9 then checksum = 9 exit end if
checksum += ch*w
digits += 1
w = 4-w
end if
end for
checksum = remainder(checksum,10)
string gb = iff(digits=13 and checksum=0 ? "good" : "bad")
printf(1,"%s: %s\n",{isbn,gb})
end procedure
 
constant isbns = {"978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083",
"978-2-74839-908-0","978-2-74839-908-5","978 1 86197 876 9"}
for i=1 to length(isbns) do check_isbn13(isbns[i]) end for
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad
978-2-74839-908-0: good
978-2-74839-908-5: bad
978 1 86197 876 9: good

PicoLisp[edit]

(de isbn13? (S)
(let L
(make
(for N (chop S)
(and (format N) (link @)) ) )
(and
(= 13 (length L))
(=0 (% (sum * L (circ 1 3)) 10)) ) ) )
(mapc
'((A)
(tab
(-19 1)
A
(if (isbn13? A) 'ok 'fail) ) )
(quote
"978-1734314502"
"978-1734314509"
"978-1-86197-876-9"
"978-2-74839-908-5"
"978 1 86197 876 9" ) )
Output:
978-1734314502     ok
978-1734314509     fail
978-1-86197-876-9  ok
978-2-74839-908-5  fail
978 1 86197 876 9  ok

PL/M[edit]

100H:
 
CHECK$ISBN13: PROCEDURE (PTR) BYTE;
DECLARE PTR ADDRESS, ISBN BASED PTR BYTE;
DECLARE (I, F, T) BYTE;
F = 1;
T = 0;
DO I = 0 TO 13;
IF I = 3 THEN DO;
/* THIRD CHAR SHOULD BE '-' */
IF ISBN(I) <> '-' THEN RETURN 0;
END;
ELSE DO;
/* DIGITS MUST BE VALID */
IF ISBN(I) < '0' OR ISBN(I) > '9' THEN RETURN 0;
T = T + (ISBN(I) - '0') * F;
F = 4 - F; /* MULTIPLY BY 1 AND 3 ALTERNATELY */
END;
END;
RETURN (T MOD 10) = 0;
END CHECK$ISBN13;
 
/* CP/M BDOS CALL */
BDOS: PROCEDURE (FUNC, ARG);
DECLARE FUNC BYTE, ARG ADDRESS;
GO TO 5;
END BDOS;
 
PRINT: PROCEDURE (STR);
DECLARE STR ADDRESS;
CALL BDOS(9, STR);
END PRINT;
 
/* TESTS */
DECLARE TEST (4) ADDRESS;
TEST(0) = .'978-1734314502$';
TEST(1) = .'978-1734314509$';
TEST(2) = .'978-1788399081$';
TEST(3) = .'978-1788399083$';
 
DECLARE I BYTE;
DO I = 0 TO LAST(TEST);
CALL PRINT(TEST(I));
CALL PRINT(.': $');
IF CHECK$ISBN13(TEST(I)) THEN
CALL PRINT(.'GOOD$');
ELSE
CALL PRINT(.'BAD$');
CALL PRINT(.(13,10,'$'));
END;
 
CALL BDOS(0,0);
EOF
Output:
978-1734314502: GOOD
978-1734314509: BAD
978-1788399081: GOOD
978-1788399083: BAD

PureBasic[edit]

Macro TestISBN13(X)  
Print(X)
If IsISBN13(X) : PrintN(" good") : Else : PrintN(" bad") : EndIf
EndMacro
 
Procedure.b IsISBN13(ISBN13.s)
ISBN13=Left(ISBN13,3)+Mid(ISBN13,5)
If IsNAN(Val(ISBN13)) Or Len(ISBN13)<>13 : ProcedureReturn #False : EndIf
Dim ISBN.s{1}(12) : PokeS(@ISBN(),ISBN13)
For i=0 To 11 Step 2 : sum+Val(ISBN(i))+Val(ISBN(i+1))*3 : Next
sum+Val(ISBN(12))
ProcedureReturn Bool(sum%10=0)
EndProcedure
 
If OpenConsole()
TestISBN13("978-1734314502")
TestISBN13("978-1734314509")
TestISBN13("978-1788399081")
TestISBN13("978-1788399083")
Input()
EndIf
Output:
978-1734314502 good
978-1734314509 bad
978-1788399081 good
978-1788399083 bad

Python[edit]

def is_isbn13(n):
n = n.replace('-','').replace(' ', '')
if len(n) != 13:
return False
product = (sum(int(ch) for ch in n[::2])
+ sum(int(ch) * 3 for ch in n[1::2]))
return product % 10 == 0
 
if __name__ == '__main__':
tests = '''
978-1734314502
978-1734314509
978-1788399081
978-1788399083'''
.strip().split()
for t in tests:
print(f"ISBN13 {t} validates {is_isbn13(t)}")
Output:
ISBN13 978-1734314502 validates True
ISBN13 978-1734314509 validates False
ISBN13 978-1788399081 validates True
ISBN13 978-1788399083 validates False


Or, expressed in terms of itertools.cycle

'''ISBN13 check digit'''
 
 
from itertools import cycle
 
 
# isISBN13 :: String -> Bool
def isISBN13(s):
'''True if s is a valid ISBN13 string
'''

digits = [int(c) for c in s if c.isdigit()]
return 13 == len(digits) and (
0 == sum(map(
lambda f, x: f(x),
cycle([
lambda x: x,
lambda x: 3 * x
]),
digits
)) % 10
)
 
 
# ------------------------- TEST -------------------------
# main :: IO ()
def main():
'''Test strings for ISBN-13 validity.'''
 
print('\n'.join(
repr((s, isISBN13(s))) for s
in ["978-1734314502",
"978-1734314509",
"978-1788399081",
"978-1788399083"
]
))
 
 
# MAIN ---
if __name__ == '__main__':
main()
 
Output:
('978-1734314502', True)
('978-1734314509', False)
('978-1788399081', True)
('978-1788399083', False)

Quackery[edit]

[ char 0 char 9 1+ within ]  is digit?    ( c --> b )
 
[ 1 & ] is odd? ( n --> b )
 
[ [] swap ]'[ swap
witheach [
dup nested
unrot over do
iff [ dip join ]
else nip
] drop ] is filter ( [ --> [ )
 
[ 0 swap
witheach [
char->n i^ odd?
iff [ 3 * + ]
else +
] ] is checksum ( $ --> n )
 
[ filter digit?
dup size 13 = not
iff [ drop false ] done
checksum 10 mod 0 = ] is isbn ( $ --> b )
 
[ dup echo$ say ": " isbn
iff [ say "Good" ]
else [ say "Bad" ] cr ] is isbn-test ( $ --> )
 
$ '978-1734314502' isbn-test
$ '978-1734314509' isbn-test
$ '978-1788399081' isbn-test
$ '978-1788399083' isbn-test
Output:
978-1734314502: Good
978-1734314509: Bad
978-1788399081: Good
978-1788399083: Bad

Racket[edit]

#lang racket/base
 
(define (isbn13-check-digit-valid? s)
(zero? (modulo (for/sum ((i (in-naturals))
(d (regexp-replace* #px"[^[:digit:]]" s "")))
(* (- (char->integer d) (char->integer #\0))
(if (even? i) 1 3)))
10)))
 
(module+ test
(require rackunit)
(check-true (isbn13-check-digit-valid? "978-1734314502"))
(check-false (isbn13-check-digit-valid? "978-1734314509"))
(check-true (isbn13-check-digit-valid? "978-1788399081"))
(check-false (isbn13-check-digit-valid? "978-1788399083")))
Output:

no output indicates tests pass

Raku[edit]

(formerly Perl 6)

Works with: Rakudo version 2019.11

Also test a value that has a zero check digit.

sub check-digit ($isbn) {
(10 - (sum (|$isbn.comb(/<[0..9]>/)) »*» (1,3)) % 10).substr: *-1
}
 
{
my $check = .substr(*-1);
my $check-digit = check-digit .chop;
say "$_ : ", $check == $check-digit ??
'Good' !!
"Bad check-digit $check; should be $check-digit"
} for words <
978-1734314502
978-1734314509
978-1788399081
978-1788399083
978-2-74839-908-0
978-2-74839-908-5
>;
Output:
978-1734314502 : Good
978-1734314509 : Bad check-digit 9; should be 2
978-1788399081 : Good
978-1788399083 : Bad check-digit 3; should be 1
978-2-74839-908-0 : Good
978-2-74839-908-5 : Bad check-digit 5; should be 0

REXX[edit]

A couple of additional checks were made to verify a correct length,   and also that the ISBN-13 code is all numerics   (with optional minus signs).

/*REXX pgm validates the check digit of an ISBN─13 code  (it may have embedded minuses).*/
parse arg $ /*obtain optional arguments from the CL*/
if $='' | if $="," then $= '978-1734314502 978-1734314509 978-1788399081 978-1788399083'
@ISBN= "ISBN─13 code isn't" /*a literal used when displaying msgs. */
/* [↓] remove all minuses from X code.*/
do j=1 for words($); y= word($,j) /*obtain an ISBN─13 code from $ list.*/
x= space( translate(y, , '-'), 0) /*remove all minus signs from the code.*/
L= length(x) /*obtain the length of the ISBN-13 code*/
if L \== 13 then do; say @ISBN '13 characters: ' x; exit 13; end
if verify(x, 9876543210)\==0 then do; say @ISBN 'numeric: ' x; exit 10; end
sum= 0
do k=1 for L; #= substr(x, k, 1) /*get a decimal digit from the X code. */
if \(k//2) then #= # * 3 /*multiply every other digit by three. */
sum= sum + # /*add the digit (or product) to the SUM*/
end /*k*/
 
if right(sum, 1)==0 then say ' ISBN-13 code ' x " is valid."
else say ' ISBN-13 code ' x " isn't valid."
end /*j*/ /*stick a fork in it, we're all done. */
output   when using the four default inputs:
     ISBN-13 code  9781734314502     is valid.
     ISBN-13 code  9781734314509  isn't valid.
     ISBN-13 code  9781788399081     is valid.
     ISBN-13 code  9781788399083  isn't valid.

Ring[edit]

 
load "stdlib.ring"
 
isbn = ["978-1734314502","978-1734314509", "978-1788399081", "978-1788399083","978-2-74839-908-0","978-2-74839-908-5","978 1 86197 876 9"]
 
for n = 1 to len(isbn)
sum = 0
isbnStr = isbn[n]
isbnStr = substr(isbnStr,"-","")
isbnStr = substr(isbnStr," ","")
for m = 1 to len(isbnStr)
if m%2 = 0
num = 3*number(substr(isbnStr,m,1))
sum = sum + num
else
num = number(substr(isbnStr,m,1))
sum = sum + num
ok
next
if sum%10 = 0
see "" + isbn[n] + ": true" + nl
else
see "" + isbn[n] + ": bad" + nl
ok
next
 

Output:

978-1734314502: true
978-1734314509: bad
978-1788399081: true
978-1788399083: bad
978-2-74839-908-0: true
978-2-74839-908-5: bad
978 1 86197 876 9: true

Ruby[edit]

def validISBN13?(str)
cleaned = str.delete("^0-9").chars
return false unless cleaned.size == 13
cleaned.each_slice(2).sum{|d1, d2| d1.to_i + 3*d2.to_i }.remainder(10) == 0
end
 
isbns = ["978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"]
isbns.each{|isbn| puts "#{isbn}: #{validISBN13?(isbn)}" }
 
Output:
978-1734314502: true
978-1734314509: false
978-1788399081: true
978-1788399083: false

Rust[edit]

fn main() {
let isbns = ["978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"];
isbns.iter().for_each(|isbn| println!("{}: {}", isbn, check_isbn(isbn)));
}
 
fn check_isbn(isbn: &str) -> bool {
if isbn.chars().filter(|c| c.is_digit(10)).count() != 13 {
return false;
}
let checksum = isbn.chars().filter_map(|c| c.to_digit(10))
.zip([1, 3].iter().cycle())
.fold(0, |acc, (val, fac)| acc + val * fac);
checksum % 10 == 0
}
 
Output:
978-1734314502: true
978-1734314509: false
978-1788399081: true
978-1788399083: false

Seed7[edit]

$ include "seed7_05.s7i";
 
const func boolean: isISBN13 (in var string: input) is func
result
var boolean: isbn is FALSE;
local
var char: c is ' ';
var integer: digit is 0;
var integer: i is 1;
var integer: sum is 0;
begin
input := replace(input, " ", "");
input := replace(input, "-", "");
if length(input) = 13 then
for c range input do
digit := ord(c) - 48;
if not odd(i) then
digit *:= 3;
end if;
sum +:= digit;
incr(i);
end for;
isbn := sum rem 10 = 0;
end if;
end func;
 
const proc: main is func
local
var string: str is "";
begin
for str range [] ("978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083") do
writeln(str <& ": " <& isISBN13(str));
end for;
end func;
Output:
978-1734314502: TRUE
978-1734314509: FALSE
978-1788399081: TRUE
978-1788399083: FALSE

Standard ML[edit]

local
fun check (c, p as (m, n)) =
if Char.isDigit c then
(not m, (if m then 3 * (ord c - 48) else ord c - 48) + n)
else
p
in
fun checkISBN s =
Int.rem (#2 (CharVector.foldl check (false, 0) s), 10) = 0
end
 
val test = ["978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"]
val () = (print
o concat
o map (fn s => s ^ (if checkISBN s then ": good\n" else ": bad\n"))) test
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad

Swift[edit]

func checkISBN(isbn: String) -> Bool {
guard !isbn.isEmpty else {
return false
}
 
let sum = isbn
.compactMap({ $0.wholeNumberValue })
.enumerated()
.map({ $0.offset & 1 == 1 ? 3 * $0.element : $0.element })
.reduce(0, +)
 
return sum % 10 == 0
}
 
let cases = [
"978-1734314502",
"978-1734314509",
"978-1788399081",
"978-1788399083"
]
 
for isbn in cases {
print("\(isbn) => \(checkISBN(isbn: isbn) ? "good" : "bad")")
}


Output:
978-1734314502 => good
978-1734314509 => bad
978-1788399081 => good
978-1788399083 => bad

Tcl[edit]

 
proc validISBN13 code {
regsub -all {\D} $code "" code ;# remove non-digits
if {[string length $code] == 13} {
set sum 0
set fac 1
foreach digit [split $code ""] {
set sum [expr {$sum + $digit * $fac}]
set fac [expr {$fac == 1? 3: 1}]
}
if {$sum % 10 == 0} {return true}
}
return false
}
foreach test {
978-1734314502
978-1734314509
978-1788399081
978-1788399083
} {puts $test:[validISBN13 $test]}
 
Output:
978-1734314502:true
978-1734314509:false
978-1788399081:true
978-1788399083:false

Simpler variant, using two loop vars and constant factors; same output:

 
proc validISBN13 code {
regsub -all {\D} $code "" code ;# remove non-digits
if {[string length $code] == 13} {
set sum 0
foreach {d1 d2} [split $code ""] {
if {$d2 eq ""} {set d2 0} ;# last round
set sum [expr {$sum + $d1 + $d2 * 3}]
}
if {$sum % 10 == 0} {return true}
}
return false
}
 

UNIX Shell[edit]

Works with: Bourne Again Shell
check_isbn13 () {
local i n t
n=${1//[^0-9]/}
t=0
for ((i=0; i<${#n}; ++i )); do
(( t += ${n:i:1}*(1 + ((i&1)<<1)) ))
done
(( 0 == t % 10 ))
}
 
for isbn in 978-1734314502 978-1734314509 978-1788399081 978-1788399083; do
printf '%s: ' "$isbn"
if check_isbn13 "$isbn"; then
printf '%s\n' OK
else
printf '%s\n' 'NOT OK'
fi
done
Output:
978-1734314502: OK
978-1734314509: NOT OK
978-1788399081: OK
978-1788399083: NOT OK

Visual Basic .NET[edit]

Translation of: C#
Module Module1
 
Function CheckISBN13(code As String) As Boolean
code = code.Replace("-", "").Replace(" ", "")
If code.Length <> 13 Then
Return False
End If
Dim sum = 0
For Each i_d In code.Select(Function(digit, index) (index, digit))
Dim index = i_d.index
Dim digit = i_d.digit
If Char.IsDigit(digit) Then
sum += (Asc(digit) - Asc("0")) * If(index Mod 2 = 0, 1, 3)
Else
Return False
End If
Next
Return sum Mod 10 = 0
End Function
 
Sub Main()
Console.WriteLine(CheckISBN13("978-1734314502"))
Console.WriteLine(CheckISBN13("978-1734314509"))
Console.WriteLine(CheckISBN13("978-1788399081"))
Console.WriteLine(CheckISBN13("978-1788399083"))
End Sub
 
End Module
Output:
True
False
True
False

Wren[edit]

var isbn13 = Fn.new { |s|
var cps = s.codePoints
var digits = []
// extract digits
for (i in 0...cps.count) {
var c = cps[i]
if (c >= 48 && c <= 57) digits.add(c)
}
// do calcs
var sum = 0
for (i in 0...digits.count) {
var d = digits[i] - 48
sum = sum + ((i%2 == 0) ? d : 3 * d)
}
return sum % 10 == 0
}
 
var tests = ["978-1734314502", "978-1734314509", "978-1788399081", "978-1788399083"]
for (test in tests) {
System.print("%(test) -> %(isbn13.call(test) ? "good" : "bad")")
}
Output:
978-1734314502 -> good
978-1734314509 -> bad
978-1788399081 -> good
978-1788399083 -> bad

XPL0[edit]

include xpllib;         \contains StrLen function
 
proc ISBN13(Str); \Show if International Standard Book Number is good
char Str;
int Sum, Cnt, Dig, I;
[Sum:= 0; Cnt:= 0;
for I:= 0 to StrLen(Str)-1 do
[Dig:= Str(I) - ^0;
if Dig>=0 & Dig<=9 then
[Sum:= Sum + Dig;
Cnt:= Cnt + 1;
if (Cnt&1) = 0 then
Sum:= Sum + Dig + Dig;
];
];
Text(0, Str);
Text(0, if rem(Sum/10)=0 & Cnt=13 then ": good" else ": bad");
CrLf(0);
];
 
[ISBN13("978-1734314502");
ISBN13("978-1734314509");
ISBN13("978-1788399081");
ISBN13("978-1788399083");
ISBN13("978-1-59327-220-3");
ISBN13("978-178839918");
]
Output:
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad
978-1-59327-220-3: good
978-178839918: bad

zkl[edit]

fcn ISBN13_check(isbn){  // "978-1734314502", throws on invalid digits
var [const] one3=("13"*6 + 1).split("").apply("toInt"); // examine 13 digits
// one3=("13"*6) if you want to calculate what the check digit should be
one3.zipWith('*,isbn - " -").sum(0) % 10 == 0
}
isbns:=
#<<<"
978-1734314502
978-1734314509
978-1788399081
978-1788399083
978-2-74839-908-0
978-2-74839-908-5".split("\n");
#<<<
foreach isbn in (isbns)
{ println(isbn.strip()," ",ISBN13_check(isbn) and " Good" or " Bad") }
Output:
978-1734314502   Good
978-1734314509   Bad
978-1788399081   Good
978-1788399083   Bad
978-2-74839-908-0   Good
978-2-74839-908-5   Bad