ISBN13 check digit: Difference between revisions

Content added Content deleted
(Added uBasic/4tH version)
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{{task}}
{{task}}


;Task:
;Task:
Validate the check digit of an ISBN-13 code:
Validate the check digit of an ISBN-13 code:
::*   Multiply every other digit by  '''3'''.
::*   Multiply every other digit by  '''3'''.
::*   Add these numbers and the other digits.
::*   Add these numbers and the other digits.
::*   Take the remainder of this number after division by  '''10'''.
::*   Take the remainder of this number after division by  '''10'''.
::*   If it is  '''0''',   the ISBN-13 check digit is correct.
::*   If it is  '''0''',   the ISBN-13 check digit is correct.


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978-1788399083 (bad)
978-1788399083 (bad)
</pre>
</pre>

=={{header|Cowgol}}==
=={{header|Cowgol}}==
<lang cowgol>include "cowgol.coh";
<lang cowgol>include "cowgol.coh";
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978-1788399083: bad
978-1788399083: bad
</pre>
</pre>

=={{header|Julia}}==
=={{header|Julia}}==
<lang julia>function isbncheck(str)
<lang julia>function isbncheck(str)
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978-1788399083: bad
978-1788399083: bad
</pre>
</pre>

=={{header|Pascal}}==
{{works with|Extended Pascal}}
<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('978-1734314502'));
writeLn(isValidISBNString('978-1734314509'));
writeLn(isValidISBNString('978-1788399081'));
writeLn(isValidISBNString('978-1788399083'))
end.</lang>
{{out}}
<pre>True
False
True
False</pre>


=={{header|Perl}}==
=={{header|Perl}}==
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0 OK, 0:339</pre>
0 OK, 0:339</pre>

=={{header|UNIX Shell}}==
=={{header|UNIX Shell}}==
{{works with|Bourne Again Shell}}
{{works with|Bourne Again Shell}}
Retrieved from "https://rosettacode.org/wiki/ISBN13_check_digit"