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ISISBN.C
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C/C++ Source or Header
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1997-07-05
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840b
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46 lines
/* +++Date last modified: 05-Jul-1997 */
/*
** ISISBN.C - Validate International Standard Book Numbers (ISBNs)
**
** public domain by Maynard Hogg
*/
#include <ctype.h>
#include "isisbn.h"
int isbn2(char *str)
{
int i = 0;
int test = 0;
int c;
while ('\0' != (c = *str++))
{
if (isdigit(c))
c -= '0';
else if (i == 9 && 'X' == c)
c = 10;
else continue;
test += c * ++i;
}
return (i == 10 && test % 11 == 0);
}
#ifdef TEST
#include <stdio.h>
main(int argc, char *argv[])
{
while (--argc)
{
int r = isbn2(*++argv);
printf("%s is%s a valid ISBN number\n", *argv, r ? "" : " not");
}
return 0;
}
#endif /* TEST */