K&R2 , section 5.4

[arnuld]

PURPOSE: see comments.
OUTPUT: negative integer as output even for equal strings
/* A string comparison function from K&R2
* example code from section 5.4,page 106
*
* returns +ve number , if 1st string is greater than 2nd
* return -ve number, if 2nd string is greater than 1st
* returns 0, if both are equal
*
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum MAXSIZE { ARR_SIZE = 1000 };
int my_strcmp( char*, char* );

int main( )
{
char s1[ARR_SIZE], s2[ARR_SIZE];

strcpy( s1, "s" );
strcpy( s2, "s" );

printf( "%s\t%s\t --%d\n", s1, s2, my_strcmp( s1, s2 ));
return EXIT_SUCCESS;
}

int my_strcmp( char* s1, char* s2 )
{
for( ; *s1 == *s2; s1++, s2++ )
{
if( s1 == '\0' )
{
return 0;
}
}

return *s1 - *s2;
}

/*

if( *s1 *s2 )
{
return 1;
}
else if( *s1 < *s2 )
{
return -1;
}
else
{
return 0;
}
*/
==================== OUTPUT ======================
Welcome to the Emacs shell

/home/arnuld/programs/C $ gcc -ansi -pedantic -Wall -Wextra section_5-5.c
/home/arnuld/programs/C $ ./a.out
s s ---151
/home/arnuld/programs/C $ ./a.out
s s ---66
/home/arnuld/programs/C $ ./a.out
s s ---122
/home/arnuld/programs/C $ ./a.out
s s ---193
/home/arnuld/programs/C $


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[Irrwahn Grausewitz]

arnuld schrieb:

PURPOSE: see comments.
OUTPUT: negative integer as output even for equal strings
/* A string comparison function from K&R2
* example code from section 5.4,page 106
*
* returns +ve number , if 1st string is greater than 2nd
* return -ve number, if 2nd string is greater than 1st
* returns 0, if both are equal
*
*/

[SNIP]

int my_strcmp( char* s1, char* s2 )
{
for( ; *s1 == *s2; s1++, s2++ )
{
if( s1 == '\0' )

Oops. I think you want:

if ( *s1 == '\0' )

{
return 0;
}
}

return *s1 - *s2;
}

--
Irrwahn Grausewitz [ir*******@freenet.de]