ISBN13 check digit: Difference between revisions
Added XPL0 example.
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ISBN-13 code 9781788399081 is valid.
ISBN-13 code 9781788399083 isn't valid.
</pre>
=={{header|XPL0}}==
<lang XPL0>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");
]</lang>
{{out}}
<pre>
978-1734314502: good
978-1734314509: bad
978-1788399081: good
978-1788399083: bad
978-1-59327-220-3: good
978-178839918: bad
</pre>
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