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sign.c
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sign.c
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/*@ assigns \nothing;
ensures \result == 0 || \result == 1 || \result == -1;
behavior positive:
assumes x > 0;
ensures \result == 1;
behavior zero:
assumes x == 0;
ensures \result == 0;
behavior negative:
assumes x < 0;
ensures \result == -1;
complete behaviors;
disjoint behaviors;
*/
int spec_sign(int x)
{
return (x > 0) - (x < 0);
}
/* assigns \nothing;
ensures \result == 0 || \result == 1 || \result == -1;
behavior positive:
assumes x > 0;
ensures \result == 1;
behavior zero:
assumes x == 0;
ensures \result == 0;
behavior negative:
assumes x < 0;
ensures \result == -1;
complete behaviors;
disjoint behaviors;
*/
/*int sign2(int x)
{
// assumes 32-bit int and 2s complement signed shifts work (implementation defined by C spec)
return (x>>31) | ((unsigned)-x >> 31);
}*/
#ifdef OUT_OF_TASK
#include <stdio.h>
int main(void)
{
printf("res: %d\n", spec_sign(-10));
return 0;
}
#endif