The hash set implementation in C.
#include "hashset.h"
char *foo = "foo";
char *missing = "missing";
hashset_t set = hashset_create();
if (set == NULL) {
fprintf(stderr, "failed to create hashset instance\n");
abort();
}
hashset_add(set, foo);
assert(hashset_is_member(set, foo) == 1);
assert(hashset_is_member(set, missing) == 0);