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ISBN13 check digit: Difference between revisions

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ISBN13 check digit (view source)

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{{draft task}}
 
;Task:
Validate the check digit of an ISBN-13 code. :
::*   Multiply every other digit by  '''3'''.
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.
::*   Add these numbers and the other digits.
::*   Take the remainder of this number after division by  '''10'''.
::*   If it is  '''0''',   the ISBN-13 check digit is correct.
 
 
You might use the following codes for testing:
::::*   978-0596528126       (good)
::::*   978-0596528120         (bad)
::::*   978-1788399081       (good)
::::*   978-1788399083         (bad)
 
 
Use the following codes for testing:
<pre>978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad</pre>
Show output here, on this page
;See also:
<p>See https://isbn-information.com/the-13-digit-isbn.html for details on the method of validation.
 
 
;See also:
:* &nbsp; for details: &nbsp; [https://isbn-information.com/the-13-digit-isbn.html 13-digit ISBN method of validation]. &nbsp; &nbsp; &nbsp; (installs cookies.)
<br><br>
 
=={{header|11l}}==
{{trans|Python}}
 
<syntaxhighlight lang="11l">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 = |‘978-0596528126
978-0596528120
978-1788399081
978-1788399083’.split("\n")
 
L(t) tests
print(‘ISBN13 ’t‘ validates ’is_isbn13(t))</syntaxhighlight>
 
{{out}}
<pre>
ISBN13 978-0596528126 validates 1B
ISBN13 978-0596528120 validates 0B
ISBN13 978-1788399081 validates 1B
ISBN13 978-1788399083 validates 0B
</pre>
 
=={{header|8080 Assembly}}==
 
<syntaxhighlight lang="8080asm"> 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$'
bad: db 'bad$'</syntaxhighlight>
 
{{out}}
 
<pre>A>isbn13 978-0596528126
good
A>isbn13 978-0596528120
bad
A>isbn13 978-1788399081
good
A>isbn13 978-1788399083
bad</pre>
 
=={{header|8086 Assembly}}==
 
<syntaxhighlight lang="asm"> 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$'
bad: db 'bad$'</syntaxhighlight>
 
{{out}}
 
<pre>C:\>isbn13 978-0596528126
good
C:\>isbn13 978-0596528120
bad
C:\>isbn13 978-1788399081
good
C:\>isbn13 978-1788399083
bad</pre>
 
=={{header|ABC}}==
<syntaxhighlight lang="abc">HOW TO REPORT valid.isbn13 str:
PUT {} IN digits
FOR d IN {0..9}: PUT d IN digits["`d`"]
IF #str <> 14 OR str item 4 <> '-': FAIL
PUT 1, 0 IN mul, sum
FOR c IN str|3 ^ str@5:
IF c not.in keys digits: FAIL
PUT sum + digits[c] * mul IN sum
PUT 4 - mul IN mul
REPORT sum mod 10 = 0
 
PUT {} IN tests
PUT "978-0596528126" IN tests[1]
PUT "978-0596528120" IN tests[2]
PUT "978-1788399081" IN tests[3]
PUT "978-1788399083" IN tests[4]
 
FOR test IN tests:
SELECT:
valid.isbn13 test: WRITE test^": good"/
ELSE: WRITE test^": bad"/</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
=={{header|Action!}}==
{{libheader|Action! Tool Kit}}
<syntaxhighlight lang="action!">INCLUDE "D2:CHARTEST.ACT" ;from the Action! Tool Kit
 
BYTE FUNC CheckISBN13(CHAR ARRAY t)
BYTE i,index,sum,v
 
sum=0 index=0
FOR i=1 TO t(0)
DO
v=t(i)
IF IsDigit(v) THEN
v==-'0
IF index MOD 2=1 THEN
v==*3
FI
sum==+v
index==+1
ELSEIF v#' AND v#'- THEN
RETURN (0)
FI
OD
IF index#13 OR sum MOD 10#0 THEN
RETURN (0)
FI
RETURN (1)
 
PROC Test(CHAR ARRAY t)
BYTE correct
 
correct=CheckISBN13(t)
Print(t) Print(" is ")
IF correct THEN
PrintE("correct")
ELSE
PrintE("incorrect")
FI
RETURN
 
PROC Main()
Put(125) PutE() ;clear screen
 
Test("978-0596528126")
Test("978-0596528120")
Test("978-1788399081")
Test("978-1788399083")
RETURN</syntaxhighlight>
{{out}}
[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/ISBN13_check_digit.png Screenshot from Atari 8-bit computer]
<pre>
978-0596528126 is correct
978-0596528120 is incorrect
978-1788399081 is correct
978-1788399083 is incorrect
</pre>
 
=={{header|Ada}}==
<syntaxhighlight lang="ada">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 ("978-0596528126");
Show ("978-0596528120");
Show ("978-1788399081");
Show ("978-1788399083");
end ISBN_Check;</syntaxhighlight>
{{out}}
<pre>978-0596528126 Good
978-0596528120 Bad
978-1788399081 Good
978-1788399083 Bad</pre>
 
=={{header|ALGOL 68}}==
{{works with|ALGOL 68G|Any - tested with release 2.8.3.win32}}
<syntaxhighlight lang="algol68">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 = ( "978-0596528126", "978-0596528120", "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</syntaxhighlight>
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|APL}}==
{{works with|Dyalog APL}}
<syntaxhighlight lang="apl">check_isbn13←{
13≠⍴n←(⍵∊⎕D)/⍵:0
0=10|(⍎¨n)+.×13⍴1 3
}</syntaxhighlight>
 
{{out}}
 
<pre> check_isbn13¨ '978-0596528126' '978-0596528120' '978-1788399081' '978-1788399083'
1 0 1 0</pre>
 
=={{header|AppleScript}}==
===Composition of pure functions===
 
<syntaxhighlight lang="applescript">-------------------- 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, {"978-0596528126", "978-0596528120", ¬
"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</syntaxhighlight>
{{Out}}
<pre>{{"978-0596528126", true}, {"978-0596528120", false}, {"978-1788399081", true}, {"978-1788399083", false}}</pre>
 
===Straightforward===
 
This task ''can'' be tackled very simply by working through the numeric text two characters at a time:
 
<syntaxhighlight lang="applescript">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 {"978-0596528126", "978-0596528120", "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</syntaxhighlight>
 
{{output}}
<pre>"978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad"</pre>
 
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 <tt>return</tt> line as simply: <tt>return (sum mod 10 = 0)</tt>.
 
<syntaxhighlight lang="applescript">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</syntaxhighlight>
 
=={{header|Arturo}}==
 
<syntaxhighlight lang="rebol">validISBN?: function [isbn][
currentCheck: to :integer to :string last isbn
isbn: map split chop replace isbn "-" "" 'd -> to :integer d
 
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: [
"978-0596528126" "978-0596528120"
"978-1788399081" "978-1788399083"
]
 
loop tests 'test [
print [test "=>" validISBN? test]
]</syntaxhighlight>
 
{{out}}
 
<pre>978-0596528126 => true
978-0596528120 => false
978-1788399081 => true
978-1788399083 => false</pre>
 
=={{header|AutoHotkey}}==
<syntaxhighlight lang="autohotkey">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)")
}</syntaxhighlight>
Examples:<syntaxhighlight lang="autohotkey">output := ""
nums := ["978-0596528126","978-0596528120","978-1788399081","978-1788399083"]
for i, n in nums
output .= ISBN13_check_digit(n) "`n"
MsgBox % output
return</syntaxhighlight>
{{out}}
<pre>978-0596528126 (good)
978-0596528120 (bad)
978-1788399081 (good)
978-1788399083 (bad)</pre>
 
=={{header|AWK}}==
<syntaxhighlight lang="awk">
<lang AWK>
# syntax: GAWK -f ISBN13_CHECK_DIGIT.AWK
BEGIN {
arr[++n] = "978-17343145020596528126"
arr[++n] = "978-17343145090596528120"
arr[++n] = "978-1788399081"
arr[++n] = "978-1788399083"
Line 40 ⟶ 744:
return(substr(isbn,13,1) == check_digit ? "OK" : sprintf("NG check digit S/B %d",check_digit))
}
</syntaxhighlight>
</lang>
{{out}}
<pre>
978-17343145020596528126 OK
978-17343145090596528120 NG check digit S/B 2
978-1788399081 OK
978-1788399083 NG check digit S/B 1
Line 50 ⟶ 754:
0820424528 NG length
</pre>
 
=={{header|BASIC256}}==
{{trans|Ring}}
<syntaxhighlight lang="vb">arraybase 1
dim isbn = {"978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083", "978-2-74839-908-0", "978-2-74839-908-5", "978 1 86197 876 9"}
 
for n = 1 to isbn[?]
sum = 0
isbnStr = isbn[n]
isbnStr = replace(isbnStr, "-", "")
isbnStr = replace(isbnStr, " ", "")
for m = 1 to length(isbnStr)
if m mod 2 = 0 then
num = 3 * int(mid(isbnStr, m, 1))
else
num = int(mid(isbnStr, m, 1))
end if
sum += num
next m
if sum mod 10 = 0 then
print isbn[n]; ": good"
else
print isbn[n]; ": bad"
end if
next n</syntaxhighlight>
 
=={{header|BCPL}}==
<syntaxhighlight lang="bcpl">get "libhdr"
 
let checkISBN(s) = valof
$( let tally = 0
unless s%0 = 14 resultis false
unless s%4 = '-' resultis false
for i=1 to 3
$( let digit = s%i-'0'
test i rem 2 = 0
do tally := tally + 3 * digit
or tally := tally + digit
$)
for i=5 to 14
$( let digit = s%i-'0'
test i rem 2 = 0
do tally := tally + digit
or tally := tally + 3 * digit
$)
resultis tally rem 10 = 0
$)
 
let show(s) be
writef("%S: %S*N", s, checkISBN(s) -> "good", "bad")
 
let start() be
$( show("978-0596528126")
show("978-0596528120")
show("978-1788399081")
show("978-1788399083")
$)</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|C}}==
<langsyntaxhighlight lang="c">#include <stdio.h>
 
int check_isbn13(const char *isbn) {
Line 77 ⟶ 847:
int main() {
int i;
const char* isbns[] = {"978-17343145020596528126", "978-17343145090596528120", "978-1788399081", "978-1788399083"};
for (i = 0; i < 4; ++i) {
printf("%s: %s\n", isbns[i], check_isbn13(isbns[i]) ? "good" : "bad");
}
return 0;
}</langsyntaxhighlight>
 
{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|C++}}==
{{trans|C}}
<syntaxhighlight lang="cpp">#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 = { "978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083" };
for (auto isbn : isbns) {
std::cout << isbn << ": " << (check_isbn13(isbn) ? "good" : "bad") << '\n';
}
 
return 0;
}</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|C sharp}}==
<syntaxhighlight lang="csharp">using System;
using System.Linq;
 
public class Program
{
public static void Main() {
Console.WriteLine(CheckISBN13("978-0596528126"));
Console.WriteLine(CheckISBN13("978-0596528120"));
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;
}
}
}</syntaxhighlight>
{{out}}
<pre>
True
False
True
False</pre>
 
=={{header|CLU}}==
<syntaxhighlight lang="clu">isbn13_check = proc (s: string) returns (bool)
if string$size(s) ~= 14 then return(false) end
if s[4] ~= '-' then return(false) end
begin
check: int := 0
for i: int in int$from_to(1, 14) do
if i=4 then continue end
d: int := int$parse(string$c2s(s[i]))
if i=2 cor (i>4 cand i//2=1) then d := d*3 end
check := check + d
end
return(check//10 = 0)
end except when bad_format:
return(false)
end
end isbn13_check
 
start_up = proc ()
po: stream := stream$primary_output()
tests: array[string] := array[string]$
["978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"]
for test: string in array[string]$elements(tests) do
stream$puts(po, test)
stream$puts(po, ": ")
if isbn13_check(test)
then stream$putl(po, "good")
else stream$putl(po, "bad")
end
end
end start_up</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|COBOL}}==
{{works with|GnuCOBOL}}
<syntaxhighlight lang="cobol"> ******************************************************************
* 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 '978-0596528126'.
02 FILLER PIC X(14) VALUE '978-0596528120'.
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.
</syntaxhighlight>
 
{{out}}
 
<pre>978-0596528126 (good)
978-0596528120 (bad)
978-1788399081 (good)
978-1788399083 (bad)
</pre>
 
=={{header|Cowgol}}==
<syntaxhighlight lang="cowgol">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][] := {
"978-0596528126", "978-0596528120", "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;</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|D}}==
{{trans|Kotlin}}
<syntaxhighlight lang="d">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("978-0596528126"));
assert(!isValidISBN13("978-0596528120"));
assert(isValidISBN13("978-1788399081"));
assert(!isValidISBN13("978-1788399083"));
}</syntaxhighlight>
 
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
 
 
<syntaxhighlight lang="Delphi">
 
function ValidateISBN(ISBN: string): boolean;
{Validate an ISBN number}
var I,N,Sum: integer;
begin
Sum:=0;
{Go througha chars, ignoring non-digits}
for I:=1 to Length(ISBN) do
if ISBN[I] in ['0'..'9'] then
begin
N:=StrToInt(ISBN[I]);
{Every other digit multiplied by 3}
if (I and 1)=1 then N:=N*3;
{Sum digits}
Sum:=Sum+N;
end;
{The sum must be an even multiple of 10}
Result:=(Sum mod 10)=0;
end;
 
procedure ValidateAndShow(Memo: TMemo; ISBN: string);
{Validate ISBN number and show the result}
var S: string;
begin
S:=ISBN;
if ValidateISBN(ISBN) then S:=S+' (Good)'
else S:=S+' (Bad)';
Memo.Lines.Add(S);
end;
 
procedure TestISBNSet(Memo: TMemo);
{Test supplied set of ISBN numbers}
begin
ValidateAndShow(Memo,'978-0596528126'); //(good)
ValidateAndShow(Memo,'978-0596528120'); //(bad)
ValidateAndShow(Memo,'978-1788399081'); //(good)
ValidateAndShow(Memo,'978-1788399083'); //(bad)
end;
 
 
</syntaxhighlight>
{{out}}
<pre>
978-0596528126 (Good)
978-0596528120 (Bad)
978-1788399081 (Good)
978-1788399083 (Bad)
 
</pre>
 
 
=={{header|Draco}}==
<syntaxhighlight lang="draco">proc nonrec isbn13_check(*char isbn) bool:
byte n, check, d;
char cur;
bool ok;
n := 0;
check := 0;
ok := true;
while
cur := isbn*;
isbn := isbn + 1;
ok and cur ~= '\e'
do
if n=3 then
if cur ~= '-' then ok := false fi
elif cur<'0' or cur>'9' then
ok := false
else
d := cur - '0';
if n=1 or (n>3 and n&1 = 0) then
d := d * 3;
fi;
check := check + d
fi;
n := n + 1
od;
ok and n = 14 and check%10 = 0
corp
 
proc nonrec test(*char isbn) void:
writeln(isbn, ": ",
if isbn13_check(isbn) then "good" else "bad" fi)
corp
 
proc nonrec main() void:
test("978-0596528126");
test("978-0596528120");
test("978-1788399081");
test("978-1788399083")
corp</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|EasyLang}}==
<syntaxhighlight lang="text">
func ISBN13check isbn$ .
for c$ in strchars isbn$
if c$ <> "-"
ndigs += 1
.
dig = number c$
if ndigs mod 2 = 0
dig *= 3
.
sum += dig
.
if sum mod 10 <> 0
return 0
.
return 1
.
codes$[] = [ "978-0596528126" "978-0596528120" "978-1788399081" "978-1788399083" ]
for code$ in codes$[]
if ISBN13check code$ = 1
print code$ & " is a valid ISBN"
else
print code$ & " is not a valid ISBN"
.
.
</syntaxhighlight>
{{out}}
<pre>
978-0596528126 is a valid ISBN
978-0596528120 is not a valid ISBN
978-1788399081 is a valid ISBN
978-1788399083 is not a valid ISBN
</pre>
 
=={{header|Excel}}==
===LAMBDA===
 
Binding the name '''ISBN13Check''' to the following lambda expression in the Name Manager of the Excel WorkBook:
 
(See [https://www.microsoft.com/en-us/research/blog/lambda-the-ultimatae-excel-worksheet-function/ LAMBDA: The ultimate Excel worksheet function])
 
{{Works with|Office 365 betas 2021}}
<syntaxhighlight lang="lisp">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
)
)
)</syntaxhighlight>
 
and also assuming the following generic bindings in the Name Manager for the WorkBook:
 
<syntaxhighlight lang="lisp">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)
)
)</syntaxhighlight>
 
{{Out}}
{| class="wikitable"
|-
|||style="text-align:right; font-family:serif; font-style:italic; font-size:120%;"|fx
! colspan="2" style="text-align:left; vertical-align: bottom; font-family:Arial, Helvetica, sans-serif !important;"|=ISBN13Check(A2)
|- style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff;"
|
| A
| B
|-
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 1
| style="font-weight:bold" | Candidate string
| style="font-weight:bold" | ISBN13 checked
|-
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 2
| 978-0596528126
| style="background-color:#cbcefb" | TRUE
|-
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 3
| 978-0596528120
| FALSE
|-
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 4
| 978-1788399081
| TRUE
|-
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 5
| 978-1788399083
| FALSE
|}
 
=={{header|Factor}}==
<langsyntaxhighlight lang="factor">USING: combinators.short-circuit formatting kernel math
math.functions math.parser math.vectors qw sequences sequences.extras sets
sequences.extras sets unicode ;
 
: (isbn13?) ( str -- ? )
string>digits
[ <evens> sum ] [ <odds> 3 v*n sum + ] bi 10 mod zerodivisor? ;
 
: isbn13? ( str -- ? )
Line 105 ⟶ 1,446:
{ [ length 13 = ] [ [ digit? ] all? ] [ (isbn13?) ] } 1&& ;
 
qw{ 978-17343145020596528126 978-17343145090596528120 978-1788399081 978-1788399083 }
[ dup isbn13? "good" "bad" ? "%s: %s\n" printf ] each</langsyntaxhighlight>
{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|Forth}}==
The following word not only identifies correct 13 digit ISBN (and EAN) codes, but also 8 digit EAN and GTIN codes.
<syntaxhighlight lang="text">: is-digit [char] 0 - 10 u< ;
 
: isbn? ( a n -- f)
1- chars over + 2>r 0 1 2r> ?do
dup i c@ dup is-digit \ get length and factor, setup loop
if [char] 0 - * rot + swap 3 * 8 mod else drop drop then
-1 chars +loop drop 10 mod 0= \ now calculate checksum
;</syntaxhighlight>
{{out}}
In Forth, a "true" value is indicated by "-1".
<pre>
s" 978-0596528126" isbn? . -1 ok
s" 978-0596528120" isbn? . 0 ok
s" 978-1788399081" isbn? . -1 ok
s" 978-1788399083" isbn? . 0 ok
</pre>
 
=={{header|Fortran}}==
<syntaxhighlight lang="fortran">
program isbn13
implicit none
 
character(len=14), dimension(4), parameter :: isbns=["978-0596528126", "978-0596528120", "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
</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126 : good
978-0596528120 : bad
978-1788399081 : good
978-1788399083 : bad
</pre>
 
=={{header|FreeBASIC}}==
<syntaxhighlight lang="freebasic">#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) = { "978-0596528126", "978-0596528120", "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</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|F_Sharp|F#}}==
<syntaxhighlight lang="fsharp">// ISBN13 Check Digit
open System
 
let parseInput (input: string) =
Seq.map(fun c -> c |> string) input |> Seq.toList |> List.map(fun x -> Int32.Parse x)
 
[<EntryPoint>]
let main argv =
let isbnnum = parseInput (String.filter (fun x -> x <> '-') argv.[0])
// Multiply every other digit by 3
let everyOther = List.mapi (fun i x -> if i % 2 = 0 then x * 3 else x) isbnnum
// Sum the *3 list with the original list
let sum = List.sum everyOther + List.sum isbnnum
// If the remainder of sum / 10 is 0 then it's a valid ISBN13
if sum % 10 = 0 then
printfn "%s Valid ISBN13" argv.[0]
else
printfn "%s Invalid ISBN13" argv.[0]
0</syntaxhighlight>
 
{{out}}
<pre>978-0596528126 Valid ISBN13
978-0596528120 Inalid ISBN13
978-1788399081 Valid ISBN13
978-1788399083 Inalid ISBN13</pre>
 
=={{header|Fōrmulæ}}==
 
{{FormulaeEntry|page=https://formulae.org/?script=examples/ISBN13_check_digit}}
 
'''Solution'''
 
[[File:Fōrmulæ - ISBN13 check digit 01.png]]
 
'''Test cases'''
 
[[File:Fōrmulæ - ISBN13 check digit 02.png]]
 
[[File:Fōrmulæ - ISBN13 check digit 03.png]]
 
=={{header|Gambas}}==
{{trans|BASIC256}}
<syntaxhighlight lang="vbnet">Public Sub Main()
Dim isbn As String[] = ["978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083", "978-2-74839-908-0", "978-2-74839-908-5", "978 1 86197 876 9"]
For n As Integer = 1 To isbn.Count
Dim sum As Integer = 0, num As Integer
Dim isbnStr As String = isbn[n]
isbnStr = Replace(isbnStr, "-", "")
isbnStr = Replace(isbnStr, " ", "")
For m As Integer = 1 To Len(isbnStr)
If m Mod 2 = 0 Then
num = 3 * CInt(Mid(isbnStr, m, 1))
Else
num = CInt(Mid(isbnStr, m, 1))
End If
sum += num
Next
If sum Mod 10 = 0 Then
Print isbn[n]; ": good"
Else
Print isbn[n]; ": bad"
End If
Next
End</syntaxhighlight>
 
=={{header|Go}}==
<langsyntaxhighlight lang="go">package main
 
import (
Line 148 ⟶ 1,672:
 
func main() {
isbns := []string{"978-17343145020596528126", "978-17343145090596528120", "978-1788399081", "978-1788399083"}
for _, isbn := range isbns {
res := "bad"
Line 156 ⟶ 1,680:
fmt.Printf("%s: %s\n", isbn, res)
}
}</langsyntaxhighlight>
 
{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|Haskell}}==
<syntaxhighlight lang="haskell">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))
[ "978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
]</syntaxhighlight>
{{out}}
<pre>978-0596528126: Valid: True
978-0596528120: Valid: False
978-1788399081: Valid: True
978-1788399083: Valid: False</pre>
 
Or, expressed in terms of ''cycle'':
 
<syntaxhighlight lang="haskell">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))
[ "978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
]</syntaxhighlight>
{{Out}}
<pre>("978-0596528126",True)
("978-0596528120",False)
("978-1788399081",True)
("978-1788399083",False)</pre>
 
=={{header|IS-BASIC}}==
<syntaxhighlight lang="is-basic">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</syntaxhighlight>
 
=={{header|J}}==
<syntaxhighlight lang="j"> D =: '0123456789'
isbn13c =: D&([ check@:i. clean)
check =: 0 = 10 | lc
lc =: [ +/@:* weight
weight =: 1 3 $~ #
clean =: ] -. a. -. [</syntaxhighlight>
{{out}}
 
<syntaxhighlight lang="j"> isbn13c;._1 ' 978-0596528126 978-0596528120 978-1788399081 978-1788399083'
1 0 1 0</syntaxhighlight>
 
=={{header|Java}}==
<syntaxhighlight lang="java">
public static void main(String[] args) {
String[] isbn13s = {
"978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
};
for (String isbn13 : isbn13s)
System.out.printf("%s %b%n", isbn13, validateISBN13(isbn13));
}
 
static boolean validateISBN13(String string) {
int[] digits = digits(string.strip().replace("-", ""));
return digits[12] == checksum(digits);
}
 
static int[] digits(String string) {
int[] digits = new int[13];
int index = 0;
for (char character : string.toCharArray()) {
if (character < '0' || character > '9')
throw new IllegalArgumentException("Invalid ISBN-13");
/* convert ascii to integer */
digits[index++] = Character.digit(character, 10);
}
return digits;
}
 
static int checksum(int[] digits) {
int total = 0;
int index = 0;
for (int digit : digits) {
if (index == 12) break;
if (index++ % 2 == 1) digit *= 3;
total += digit;
}
return 10 - (total % 10);
}
</syntaxhighlight>
<pre>
978-0596528126 true
978-0596528120 false
978-1788399081 true
978-1788399083 false
</pre>
<br />
An alternate demonstration
<syntaxhighlight lang="java">public static void main(){
System.out.println(isISBN13("978-0596528126"));
System.out.println(isISBN13("978-0596528120"));
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;
}
</syntaxhighlight>{{out}}
<pre>
true
false
true
false
</pre>
 
=={{header|jq}}==
{{works with|jq}}
'''Works with gojq, the Go implementation of jq'''
<syntaxhighlight lang="jq">
def isbn_check:
def digits: tostring | explode | map( select(. >= 48 and . <= 57) | [.] | implode | tonumber);
def sum(s): reduce s as $x (null; . + $x);
digits
| . as $digits
| sum(range(0;length;2) | $digits[.]) as $one
| (3 * sum(range(1;length;2) | $digits[.])) as $two
| (($one+$two) % 10) == 0;
 
def testingcodes:
["978-0596528126", "978-0596528120",
"978-1788399081", "978-1788399083"];
testingcodes[]
| "\(.): \(if isbn_check then "good" else "bad" end)"
</syntaxhighlight>
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
Line 167 ⟶ 1,898:
 
=={{header|Julia}}==
<langsyntaxhighlight lang="julia">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 = ["978-17343145020596528126", "978-17343145090596528120",
"978-1788399081", "978-1788399083"]
 
Line 178 ⟶ 1,909:
println(code, ": ", isbncheck(code) ? "good" : "bad")
end
</langsyntaxhighlight>{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|langurK}}==
{{works with|langur|0.7.1ngn/k}}
<syntaxhighlight lang=K>digits: {x[&(x>"/")&x<":"]-"0"}
In this example, we map to multiple functions (actually 1 no-op).
isbn13c: 0=10!+/{x*(#x)#1 3} digits@
<lang langur>val .isbn13checkdigit = f(var .s) {
 
.s = replace(.s, RE/[\- ]/)
isbn13c "978-0596528126"
matching(re/^[0-9]{13}$/, .s) and
1
fold(f{+}, map([_, f .d x 3], map(f .c-'0', s2cp .s))) rem 10 == 0
isbn13c "978-0596528120"
0
isbn13c " 978-1788399081"
1
isbn13c "978-1788399083"
0</syntaxhighlight>
 
=={{header|Kotlin}}==
<syntaxhighlight lang="kotlin">
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
}
</syntaxhighlight>
 
Tested using Spek
val .tests = h{
<syntaxhighlight lang="kotlin">
"978-1734314502": true,
describe("ISBN Utilities") {
"978-1734314509": false,
mapOf(
"978-1788399081": true,
"978-17883990830596528126": falseto true,
"978-0596528120" 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)
}
}
}
</syntaxhighlight>
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|langur}}==
for .key in sort(keys .tests) {
In this example, we map to multiple functions (actually 1 no-op).
val .pass = .isbn13checkdigit(.key)
<syntaxhighlight lang="langur">val .isbn13checkdigit = fn(var .s) {
write .key, ": ", if(.pass: "good"; "bad")
writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")
}</lang>
 
{{works with|langur|0.7.0}}
In this example, we set a for loop value as it progresses.
<lang langur>val .isbn13checkdigit = f(var .s) {
.s = replace(.s, RE/[\- ]/)
var .alts -> =re/^[0-9]{13}$/ trueand
matching fold(re/^fn{+}, map [0-9]_, fn{13*3}$/], s2n .s) anddiv 10
for[=0] .d in map(f .c-'0', s2cp .s) { _for += if(.alt=not .alt: .d x 3; .d) } rem 10 == 0
}
 
val .tests = h{
"978-17343145020596528126": true,
"978-17343145090596528120": false,
"978-1788399081": true,
"978-1788399083": false,
}
 
for .key in sort(keysof .tests) {
val .pass = .isbn13checkdigit(.key)
write .key, ": ", if(.pass: "good"; "bad")
writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")
}</langsyntaxhighlight>
 
{{out}}
{{works with|langur|0.6.13}}
<pre>978-0596528126: good
<lang langur>val .isbn13checkdigit = f(.n) {
978-0596528120: bad
val .s = replace .n, RE/[\- ]/
978-1788399081: good
if not matching(re/^[0-9]{13}$/, .s) {
978-1788399083: bad</pre>
 
=={{header|Lua}}==
{{trans|C}}
<syntaxhighlight lang="lua">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 multiply(sum every% other10) number== by 30
end
val .nums = map(
f(.i, .d) if(.i rem 2 == 0: .d x 3; .d),
1..13,
map f .c-'0', s2cp .s,
)
fold(f{+}, .nums) rem 10 == 0
}
 
function test(isbn)
val .tests = h{
if checkIsbn13(isbn) then
"978-1734314502": true,
"978-1734314509 print(isbn .. ": false,good")
else
"978-1788399081": true,
"978-1788399083 print(isbn .. ": false,bad")
end
}
end
 
function main()
for .key in sort(keys .tests) {
test("978-0596528126")
val .pass = .isbn13checkdigit(.key)
test("978-0596528120")
write .key, ": ", if(.pass: "good"; "bad")
test("978-1788399081")
writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")
test("978-1788399083")
}</lang>
end
 
main()</syntaxhighlight>
{{out}}
<pre>978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
 
=={{header|Mathematica}} / {{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">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["978-0596528126"]
ValidISBNQ["978-0596528120"]
ValidISBNQ["978-1788399081"]
ValidISBNQ["978-1788399083"]</syntaxhighlight>
{{out}}
<pre>True
False
True
False</pre>
 
=={{header|MiniScript}}==
This GUI implementation is for use with [http://miniscript.org/MiniMicro Mini Micro].
<syntaxhighlight lang="miniscript">
isISBN13 = function(n)
n = n.replace("-","").replace(" ","")
s = 0
for i in range(0, n.len-1,2)
s += n[i].val
end for
for i in range(1, n.len-1,2)
s += n[i].val * 3
end for
return not (s % 10)
end function
 
testValues = "978-0596528126 978-0596528120 978-1788399081 978-1788399083".split(" ")
for val in testValues
print val + " " + ["bad", "good"][isISBN13(val)]
end for
</syntaxhighlight>
{{out}}
<pre>
978-0596528126 good
978-0596528120 bad
978-1788399081 good
978-1788399083 bad</pre>
 
=={{header|Miranda}}==
<syntaxhighlight lang="miranda">main :: [sys_message]
main = [Stdout (lay (map test tests))]
 
test :: [char]->[char]
test isbn = isbn ++ ": good", if isbn13 isbn
= isbn ++ ": bad", otherwise
 
tests :: [[char]]
tests = ["978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"]
 
isbn13 :: [char]->bool
isbn13 str = False, if #isbn ~= 13 \/ ~and (map digit isbn)
= check mod 10 = 0, otherwise
where isbn = filter (~= '-') str
digits = map (numval.(:[])) isbn
check = sum (zipwith (*) digits (concat (repeat [1,3])))
 
uncurry :: (*->**->***)->(*,**)->***
uncurry f (a,b) = f a b
 
zipwith :: (*->**->***)->[*]->[**]->[***]
zipwith f a b = map (uncurry f) (zip2 a b)</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|Modula-2}}==
<syntaxhighlight lang="modula2">MODULE ISBN;
FROM InOut IMPORT WriteString, WriteLn;
FROM Strings IMPORT Length;
 
PROCEDURE validISBN(s: ARRAY OF CHAR): BOOLEAN;
VAR total, i, length: CARDINAL;
BEGIN
total := 0;
length := Length(s);
IF (length # 14) OR (s[3] # '-') THEN
RETURN FALSE;
END;
FOR i := 0 TO length-1 DO
IF i # 3 THEN
IF (s[i] < '0') OR (s[i] > '9') THEN
RETURN FALSE;
ELSIF (i < 3) AND (i MOD 2 = 1) OR (i > 3) AND (i MOD 2 = 0) THEN
total := total + 3 * (ORD(s[i]) - ORD('0'));
ELSE
total := total + ORD(s[i]) - ORD('0');
END;
END;
END;
RETURN total MOD 10 = 0;
END validISBN;
 
PROCEDURE check(s: ARRAY OF CHAR);
BEGIN
WriteString(s);
WriteString(': ');
IF validISBN(s) THEN
WriteString('good');
ELSE
WriteString('bad');
END;
WriteLn;
END check;
 
BEGIN
check('978-0596528126');
check('978-0596528120');
check('978-1788399081');
check('978-1788399083');
END ISBN.</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|Nanoquery}}==
{{trans|Go}}
<syntaxhighlight lang="nanoquery">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 = {"978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083"}
for isbn in isbns
res = "bad"
if checkIsbn13(isbn)
res = "good"
end
 
print format("%s: %s\n", isbn, res)
end</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|Nim}}==
<syntaxhighlight lang="nim">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 = [ "978-0596528126", "978-0596528120",
"978-1788399081", "978-1788399083" ]
for isbn in isbns:
var quality: string = if is_isbn(isbn): "good" else: "bad"
echo &"{isbn}: {quality}"</syntaxhighlight>
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|Pascal}}==
{{works with|Extended Pascal}}
<syntaxhighlight lang="pascal">program ISBNChecksum(output);
 
const
codeIndexMaximum = 17;
ISBNIndexMinimum = 1;
ISBNIndexMaximum = 13;
ISBNIndexRange = ISBNIndexMaximum - ISBNIndexMinimum + 1;
 
type
code = string(codeIndexMaximum);
codeIndex = 1..codeIndexMaximum value 1;
decimalDigit = '0'..'9';
decimalValue = 0..9;
ISBNIndex = ISBNIndexMinimum..ISBNIndexMaximum;
ISBN = array[ISBNIndex] of decimalDigit;
 
{ returns the integer value represented by a character }
function numericValue(protected c: decimalDigit): decimalValue;
begin
{ in Pascal result variable bears the same name as the function }
numericValue := ord(c) - ord('0')
end;
 
{ determines whether an ISBN is technically valid (checksum correct) }
function isValidISBN(protected n: ISBN): Boolean;
var
sum: 0..225 value 0;
i: ISBNIndex;
begin
{ NB: in Pascal for-loop-limits are _inclusive_ }
for i := ISBNIndexMinimum to ISBNIndexMaximum do
begin
{ alternating scale factor 3^0, 3^1 based on Boolean }
sum := sum + numericValue(n[i]) * 3 pow ord(not odd(i))
end;
isValidISBN := sum mod 10 = 0
end;
 
{ transform '978-0-387-97649-5' into '9780387976495' }
function digits(n: code): code;
var
sourceIndex, destinationIndex: codeIndex;
begin
for sourceIndex := 1 to length(n) do
begin
if n[sourceIndex] in ['0'..'9'] then
begin
n[destinationIndex] := n[sourceIndex];
destinationIndex := destinationIndex + 1
end
end;
{ to alter a string’s length you need overwrite it completely }
digits := subStr(n, 1, destinationIndex - 1)
end;
 
{ data type coercion }
function asISBN(protected n: code): ISBN;
var
result: ISBN;
begin
unpack(n[1..length(n)], result, 1);
asISBN := result
end;
 
{ tells whether a string value contains a proper ISBN representation }
function isValidISBNString(protected hyphenatedForm: code): Boolean;
var
digitOnlyForm: code;
begin
digitOnlyForm := digits(hyphenatedForm);
{ The Extended Pascal `and_then` Boolean operator allows us }
{ to first check the length before invoking `isValidISBN`. }
isValidISBNString := (length(digitOnlyForm) = ISBNIndexRange)
and_then isValidISBN(asISBN(digitOnlyForm))
end;
 
{ === MAIN ============================================================= }
begin
writeLn(isValidISBNString('978-0596528126'));
writeLn(isValidISBNString('978-0596528120'));
writeLn(isValidISBNString('978-1788399081'));
writeLn(isValidISBNString('978-1788399083'))
end.</syntaxhighlight>
{{out}}
<pre>True
False
True
False</pre>
 
=={{header|Perl}}==
<langsyntaxhighlight lang="perl">use strict;
use warnings;
use feature 'say';
Line 275 ⟶ 2,352:
}
 
for (<978-17343145020596528126 978-17343145090596528120 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")
}</langsyntaxhighlight>
{{out}}
<pre>978-17343145020596528126 : Good
978-17343145090596528120 : 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</pre>
 
=={{header|Perl 6}}==
{{works with|Rakudo|2019.11}}
Also test a value that has a zero check digit.
 
<lang perl6>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
>;</lang>
{{out}}
<pre>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
</pre>
 
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(phixonline)-->
<lang Phix>procedure check_isbn13(string isbn)
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
integer digits = 0, checksum = 0, w = 1
<span style="color: #008080;">procedure</span> <span style="color: #000000;">check_isbn13</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">isbn</span><span style="color: #0000FF;">)</span>
for i=1 to length(isbn) do
<span style="color: #004080;">integer</span> <span style="color: #000000;">digits</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">checksum</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">w</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">1</span>
integer ch = isbn[i]
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">isbn</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
if ch!=' ' and ch!='-' then
<span style="color: #004080;">integer</span> <span style="color: #000000;">ch</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">isbn</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span>
ch -= '0'
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">!=</span><span style="color: #008000;">' '</span> <span style="color: #008080;">and</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">!=</span><span style="color: #008000;">'-'</span> <span style="color: #008080;">then</span>
if ch<0 or ch>9 then checksum = 9 exit end if
<span style="color: #000000;">ch</span> <span style="color: #0000FF;">-=</span> <span style="color: #008000;">'0'</span>
checksum += ch*w
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span> <span style="color: #008080;">or</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">></span><span style="color: #000000;">9</span> <span style="color: #008080;">then</span> <span style="color: #000000;">checksum</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">9</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
digits += 1
<span style="color: #000000;">checksum</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">*</span><span style="color: #000000;">w</span>
w = 4-w
<span style="color: #000000;">digits</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
end if
<span style="color: #000000;">w</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">4</span><span style="color: #0000FF;">-</span><span style="color: #000000;">w</span>
end for
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
checksum = remainder(checksum,10)
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
string gb = iff(digits=13 and checksum=0 ? "good" : "bad")
<span style="color: #000000;">checksum</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">remainder</span><span style="color: #0000FF;">(</span><span style="color: #000000;">checksum</span><span style="color: #0000FF;">,</span><span style="color: #000000;">10</span><span style="color: #0000FF;">)</span>
printf(1,"%s: %s\n",{isbn,gb})
<span style="color: #004080;">string</span> <span style="color: #000000;">gb</span> <span style="color: #0000FF;">=</span> <span style="color: #008080;">iff</span><span style="color: #0000FF;">(</span><span style="color: #000000;">digits</span><span style="color: #0000FF;">=</span><span style="color: #000000;">13</span> <span style="color: #008080;">and</span> <span style="color: #000000;">checksum</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #0000FF;">?</span> <span style="color: #008000;">"good"</span> <span style="color: #0000FF;">:</span> <span style="color: #008000;">"bad"</span><span style="color: #0000FF;">)</span>
end procedure
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"%s: %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">isbn</span><span style="color: #0000FF;">,</span><span style="color: #000000;">gb</span><span style="color: #0000FF;">})</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
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"}
<span style="color: #008080;">constant</span> <span style="color: #000000;">isbns</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #008000;">"978-0596528126"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"978-0596528120"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"978-1788399081"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"978-1788399083"</span><span style="color: #0000FF;">,</span>
for i=1 to length(isbns) do check_isbn13(isbns[i]) end for</lang>
<span style="color: #008000;">"978-2-74839-908-0"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"978-2-74839-908-5"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"978 1 86197 876 9"</span><span style="color: #0000FF;">}</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">isbns</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span> <span style="color: #000000;">check_isbn13</span><span style="color: #0000FF;">(</span><span style="color: #000000;">isbns</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">])</span> <span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
Line 352 ⟶ 2,401:
 
=={{header|PicoLisp}}==
<langsyntaxhighlight PicoLisplang="picolisp">(de isbn13? (S)
(let L
(make
Line 367 ⟶ 2,416:
(if (isbn13? A) 'ok 'fail) ) )
(quote
"978-17343145020596528126"
"978-17343145090596528120"
"978-1-86197-876-9"
"978-2-74839-908-5"
"978 1 86197 876 9" ) )</langsyntaxhighlight>
{{out}}
<pre>
978-17343145020596528126 ok
978-17343145090596528120 fail
978-1-86197-876-9 ok
978-2-74839-908-5 fail
978 1 86197 876 9 ok
</pre>
 
=={{header|PL/M}}==
<syntaxhighlight lang="plm">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) = .'978-0596528126$';
TEST(1) = .'978-0596528120$';
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</syntaxhighlight>
{{out}}
<pre>978-0596528126: GOOD
978-0596528120: BAD
978-1788399081: GOOD
978-1788399083: BAD</pre>
 
=={{header|PowerShell}}==
<syntaxhighlight lang="powershell">
function Get-ISBN13 {
$codes = (
"978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
)
 
foreach ($line in $codes) {
 
$sum = $null
$codeNoDash = $line.Replace("-","")
 
for ($i = 0; $i -lt $codeNoDash.length; $i++) {
 
if (($i % 2) -eq 1) {
 
$sum += [decimal]$codeNoDash[$i] * 3
}else {
 
$sum += [decimal]$codeNoDash[$i]
 
}
}
if (($sum % 10) -eq 0) {
 
Write-Host "$line Good"
}else {
 
Write-Host "$line Bad"
 
}
}
}
Get-ISBN13
</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126 Good
978-0596528120 Bad
978-1788399081 Good
978-1788399083 Bad
</pre>
 
=={{header|PureBasic}}==
<syntaxhighlight lang="purebasic">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("978-0596528126")
TestISBN13("978-0596528120")
TestISBN13("978-1788399081")
TestISBN13("978-1788399083")
Input()
EndIf</syntaxhighlight>
{{out}}
<pre>978-0596528126 good
978-0596528120 bad
978-1788399081 good
978-1788399083 bad
</pre>
 
=={{header|Python}}==
<langsyntaxhighlight lang="python">def is_isbn13(n):
n = n.replace('-','').replace(' ', '')
if len(n) != 13:
Line 392 ⟶ 2,580:
if __name__ == '__main__':
tests = '''
978-17343145020596528126
978-17343145090596528120
978-1788399081
978-1788399083'''.strip().split()
for t in tests:
print(f"ISBN13 {t} validates {is_isbn13(t)}")</langsyntaxhighlight>
 
{{out}}
<pre>ISBN13 978-17343145020596528126 validates True
ISBN13 978-17343145090596528120 validates False
ISBN13 978-1788399081 validates True
ISBN13 978-1788399083 validates False</pre>
 
 
Or, expressed in terms of ''itertools.cycle''
<syntaxhighlight lang="python">'''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 ["978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
]
))
 
 
# MAIN ---
if __name__ == '__main__':
main()
</syntaxhighlight>
{{Out}}
<pre>('978-0596528126', True)
('978-0596528120', False)
('978-1788399081', True)
('978-1788399083', False)</pre>
 
=={{header|Quackery}}==
<syntaxhighlight lang="quackery">[ 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 ( $ --> )
 
$ '978-0596528126' isbn-test
$ '978-0596528120' isbn-test
$ '978-1788399081' isbn-test
$ '978-1788399083' isbn-test</syntaxhighlight>
{{out}}
<pre>
978-0596528126: Good
978-0596528120: Bad
978-1788399081: Good
978-1788399083: Bad
</pre>
 
=={{header|Racket}}==
 
<syntaxhighlight lang="racket">#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? "978-0596528126"))
(check-false (isbn13-check-digit-valid? "978-0596528120"))
(check-true (isbn13-check-digit-valid? "978-1788399081"))
(check-false (isbn13-check-digit-valid? "978-1788399083")))</syntaxhighlight>
 
{{out}}
no output indicates tests pass
 
=={{header|Raku}}==
(formerly Perl 6)
{{works with|Rakudo|2019.11}}
Also test a value that has a zero check digit.
 
<syntaxhighlight lang="raku" line>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 <
978-0596528126
978-0596528120
978-1788399081
978-1788399083
978-2-74839-908-0
978-2-74839-908-5
>;</syntaxhighlight>
{{out}}
<pre>978-0596528126 : Good
978-0596528120 : 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
</pre>
 
=={{header|Red}}==
 
<syntaxhighlight lang="red">check_valid_isbn13: function [str] [
is_digit: charset [#"0" - #"9"]
remove-each i str [not pick is_digit i] ; remove non-digits
 
either 13 = length? str [ ; reject strings of incorrect length
sum: 0
repeat i 13 [
mul: either even? i [3] [1] ; multiplier for odd/even digits
sum: sum + (mul * to integer! to string! pick str i)
]
zero? (sum % 10) ; check if remainder mod 10 is zero
] [
false
]
]
 
; check given examples
foreach [str] ["978-0596528126" "978-0596528120" "978-1788399081" "978-1788399083"] [
prin str
prin " - "
print check_valid_isbn13 str
]
</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126 - true
978-0596528120 - false
978-1788399081 - true
978-1788399083 - false
</pre>
 
=={{header|Refal}}==
<syntaxhighlight lang="refal">$ENTRY Go {
= <Test '978-0596528126'>
<Test '978-0596528120'>
<Test '978-1788399081'>
<Test '978-1788399083'>
};
 
Test {
e.X = <Prout e.X ': ' <ISBN e.X>>;
};
 
ISBN {
e.X, <Remove '-' e.X>: e.DS,
<CheckDigits e.DS>: {
False = Bad;
True = <ISBN1 e.DS>;
};
};
 
ISBN1 {
(13 s.Sum), <Mod s.Sum 10>: 0 = Good;
(13 s.Sum) e.X = Bad;
(s.N s.Sum) = Bad;
 
(s.N s.Sum) s.D e.X,
<+ s.N 1>: s.N1,
<Numb s.D>: s.V,
<Mod s.N 2>: {
0 = <ISBN1 (s.N1 <+ s.Sum s.V>) e.X>;
1 = <ISBN1 (s.N1 <+ s.Sum <* 3 s.V>>) e.X>;
};
 
e.X = <ISBN1 (0 0) e.X>;
};
 
Remove {
s.1 = ;
s.1 s.1 e.X = <Remove s.1 e.X>;
s.1 s.2 e.X = s.2 <Remove s.1 e.X>;
};
 
CheckDigits {
= True;
s.D e.X, '0123456789': e.A s.D e.B = <CheckDigits e.X>;
e.X = False;
};</syntaxhighlight>
{{out}}
<pre>978-0596528126: Good
978-0596528120: Bad
978-1788399081: Good
978-1788399083: Bad</pre>
 
=={{header|REXX}}==
A couple of additional checks were made to verify a correct length, &nbsp; and also that the ISBN-13 code is all numerics &nbsp; (with optional minus signs).
<langsyntaxhighlight lang="rexx">/*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 $= '978-17343145020596528126 978-17343145090596528120 978-1788399081 978-1788399083'
@ISBN= "ISBN─13 code isn't" /*a literal used when displaying msgs. */
/* [↓] remove all minuses from X code.*/
Line 425 ⟶ 2,845:
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. */</langsyntaxhighlight>
{{out|output|text=&nbsp; when using the four default inputs:}}
<pre>
Line 432 ⟶ 2,852:
ISBN-13 code 9781788399081 is valid.
ISBN-13 code 9781788399083 isn't valid.
</pre>
 
=={{header|Ring}}==
<syntaxhighlight lang="ring">
load "stdlib.ring"
 
isbn = ["978-0596528126","978-0596528120", "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
</syntaxhighlight>
Output:
<pre>
978-0596528126: true
978-0596528120: 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
</pre>
 
=={{header|RPL}}==
{{works with|Halcyon Calc|4.2.7}}
≪ → isbn
≪ 0 1 CF
1 isbn SIZE FOR j
IF "0123456789" isbn j DUP SUB POS THEN
LAST 1 -
IF 1 FS?C THEN 3 * ELSE 1 SF END
+
END
NEXT
≫
10 MOD NOT
≫
'ISBN?' STO
 
≪ { "978-0596528126" "978-0596528120" "978-1788399081" "978-1788399083" } → tests
≪ 1 tests SIZE FOR j tests GET ISBN? NEXT ≫
≫ EVAL
{{out}}
<pre>
4: 1
3: 0
2: 1
1: 0
</pre>
=={{header|Ruby}}==
<syntaxhighlight lang="ruby">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 = ["978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083"]
isbns.each{|isbn| puts "#{isbn}: #{validISBN13?(isbn)}" }
</syntaxhighlight>{{out}}
<pre>978-0596528126: true
978-0596528120: false
978-1788399081: true
978-1788399083: false
</pre>
 
=={{header|Rust}}==
<syntaxhighlight lang="rust">fn main() {
let isbns = ["978-0596528126", "978-0596528120", "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
}
</syntaxhighlight>
{{out}}
<pre>
978-0596528126: true
978-0596528120: false
978-1788399081: true
978-1788399083: false
</pre>
 
=={{header|Seed7}}==
<syntaxhighlight lang="seed7">$ 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 [] ("978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083") do
writeln(str <& ": " <& isISBN13(str));
end for;
end func;</syntaxhighlight>
{{out}}
<pre>
978-0596528126: TRUE
978-0596528120: FALSE
978-1788399081: TRUE
978-1788399083: FALSE
</pre>
=={{header|SETL}}==
<syntaxhighlight lang="setl">program isbn13;
loop for test in [
"978-0596528126", "978-0596528120",
"978-1788399081", "978-1788399083"
] do
print(test + if valid_isbn13 test then ": good" else ": bad" end);
end loop;
 
op valid_isbn13(isbn);
if #isbn /= 14
or isbn(4) /= '-'
or exists c in isbn | not c in "0123456789-" then
return false;
end if;
 
m := 3;
loop for ch in isbn | ch in "0123456789" do
s +:= val ch * (m := 4 - m);
end loop;
return s mod 10 = 0;
end op;
end program;</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|Standard ML}}==
===Easy to read version===
<syntaxhighlight lang="sml">(* these type decorations are optional, you could just as well put:
fun isValidISBN s =
*)
fun isValidISBN (s : string) : bool =
let
val digits = List.filter Char.isDigit (explode s)
val nums = map (fn x => ord x - ord #"0") digits
val len = length nums
fun sumISBN [] = raise Domain
| sumISBN [x] = x
| sumISBN (x1::x2::xs) = x1 + 3*x2 + sumISBN xs
in
len = 13 andalso sumISBN nums mod 10 = 0
end
 
val test = ["978-1734314502", "978-1734314509",
"978-1788399081", "978-1788399083"]
 
fun printTest (s : string) : unit =
(print s; print (if isValidISBN s then ": good\n" else ": bad\n"))
 
fun main () = app printTest test</syntaxhighlight>
 
===Original version===
<syntaxhighlight lang="sml">let
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 = ["978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083"]
val () = (print
o concat
o map (fn s => s ^ (if checkISBN s then ": good\n" else ": bad\n"))) test</syntaxhighlight>
{{out}}
<pre>978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad</pre>
 
=={{header|Swift}}==
 
<syntaxhighlight lang="swift">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 = [
"978-0596528126",
"978-0596528120",
"978-1788399081",
"978-1788399083"
]
 
for isbn in cases {
print("\(isbn) => \(checkISBN(isbn: isbn) ? "good" : "bad")")
}</syntaxhighlight>
 
 
{{out}}
 
<pre>978-0596528126 => good
978-0596528120 => bad
978-1788399081 => good
978-1788399083 => bad</pre>
 
=={{header|Tcl}}==
 
<syntaxhighlight lang="tcl">
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 {
978-0596528126
978-0596528120
978-1788399081
978-1788399083
} {puts $test:[validISBN13 $test]}
</syntaxhighlight>
{{out}}
<pre>978-0596528126:true
978-0596528120:false
978-1788399081:true
978-1788399083:false</pre>
Simpler variant, using two loop vars and constant factors; same output:
<syntaxhighlight lang="tcl">
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
}
</syntaxhighlight>
 
=={{header|uBasic/4tH}}==
{{works with|version 3.64.0}}
<syntaxhighlight lang="text">a := "978-0596528126"
Print Show(a), Show (Iif (Func(_IsISBN (a)), "good", "bad"))
 
a := "978-0596528120"
Print Show(a), Show (Iif (Func(_IsISBN (a)), "good", "bad"))
 
a := "978-1788399081"
Print Show(a), Show (Iif (Func(_IsISBN (a)), "good", "bad"))
 
a := "978-1788399083"
Print Show(a), Show (Iif (Func(_IsISBN (a)), "good", "bad"))
 
End
 
_IsISBN
Param (1)
Local (4)
 
c@ = 0 : e@ = 1 ' set sum and multiplier
 
For b@ = Len (a@) - 1 To 0 Step -1 ' scan string in reverse
d@ = Peek(a@, b@) - Ord ("0") ' get character
If ((d@ < 0) + (d@ > 9)) = 0 Then c@ = c@ + (d@ * e@)
e@ = (e@ * 3) % 8 ' evaluate character, change multiplier
Next
 
Return ((c@ % 10) = 0) ' modulus 10 must be zero</syntaxhighlight>
{{out}}
<pre>978-0596528126 good
978-0596528120 bad
978-1788399081 good
978-1788399083 bad
 
0 OK, 0:339</pre>
 
=={{header|UNIX Shell}}==
{{works with|Bourne Again Shell}}
<syntaxhighlight lang="sh">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 978-0596528126 978-0596528120 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</syntaxhighlight>
{{Out}}
<pre>978-0596528126: OK
978-0596528120: NOT OK
978-1788399081: OK
978-1788399083: NOT OK</pre>
 
=={{header|Visual Basic .NET}}==
{{trans|C#}}
<syntaxhighlight lang="vbnet">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("978-0596528126"))
Console.WriteLine(CheckISBN13("978-0596528120"))
Console.WriteLine(CheckISBN13("978-1788399081"))
Console.WriteLine(CheckISBN13("978-1788399083"))
End Sub
 
End Module</syntaxhighlight>
{{out}}
<pre>True
False
True
False</pre>
 
=={{header|V (Vlang)}}==
{{trans|Go}}
<syntaxhighlight lang="v (vlang)">
fn check_isbn13(isbn13 string) bool {
// remove any hyphens or spaces
isbn := isbn13.replace('-','').replace(' ','')
// check length == 13
le := isbn.len
if le != 13 {
return false
}
// check only contains digits and calculate weighted sum
mut sum := 0
for i, c in isbn.split('') {
if c.int() < '0'.int() || c.int() > '9'.int() {
return false
}
if i%2 == 0 {
sum += c.int() - '0'.int()
} else {
sum += 3 * (c.int() - '0'.int())
}
}
return sum%10 == 0
}
fn main() {
isbns := ["978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083"]
for isbn in isbns {
mut res := "bad"
if check_isbn13(isbn) {
res = "good"
}
println("$isbn: $res")
}
}</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126: good
978-0596528120: bad
978-1788399081: good
978-1788399083: bad
</pre>
 
=={{header|Wren}}==
<syntaxhighlight lang="wren">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 = ["978-0596528126", "978-0596528120", "978-1788399081", "978-1788399083"]
for (test in tests) {
System.print("%(test) -> %(isbn13.call(test) ? "good" : "bad")")
}</syntaxhighlight>
 
{{out}}
<pre>
978-0596528126 -> good
978-0596528120 -> bad
978-1788399081 -> good
978-1788399083 -> bad
</pre>
 
=={{header|XPL0}}==
<langsyntaxhighlight XPL0lang="xpl0">include xpllib; \contains StrLen function
 
proc ISBN13(Str); \Show if International Standard Book Number is good
Line 455 ⟶ 3,351:
];
 
[ISBN13("978-17343145020596528126");
ISBN13("978-17343145090596528120");
ISBN13("978-1788399081");
ISBN13("978-1788399083");
ISBN13("978-1-59327-220-3");
ISBN13("978-178839918");
]</langsyntaxhighlight>
 
{{out}}
<pre>
978-17343145020596528126: good
978-17343145090596528120: bad
978-1788399081: good
978-1788399083: bad
Line 474 ⟶ 3,370:
 
=={{header|zkl}}==
<langsyntaxhighlight lang="zkl">fcn ISBN13_check(isbn){ // "978-17343145020596528126", 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
}</langsyntaxhighlight>
<langsyntaxhighlight lang="zkl">isbns:=
#<<<"
978-17343145020596528126
978-17343145090596528120
978-1788399081
978-1788399083
Line 489 ⟶ 3,385:
#<<<
foreach isbn in (isbns)
{ println(isbn.strip()," ",ISBN13_check(isbn) and " Good" or " Bad") }</langsyntaxhighlight>
{{out}}
<pre>
978-17343145020596528126 Good
978-17343145090596528120 Bad
978-1788399081 Good
978-1788399083 Bad
Langurmonkey
990

edits

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