I think they are pretty much the same, but for clarity I usually use the has_index() function instead.
I made a small testprogram for you, so that you can benchmark it youself:
int main(int argc, array(string) argv) { int len = (int)argv[1];
array x = allocate(len, random); int rpt = (int)argv[2];
int elem = -1;
werror("Running %d iterations on array of size %d\n", rpt, len);
float t = gauge { for(int i=0; i < rpt; i++) { if (search(x, elem) == -1) { ; }; } };
werror("==-1 took %fs\n", t);
t = gauge { for(int i=0; i < rpt; i++) { if (search(x, elem) < 0) { ; }; } };
werror("<0 took %fs\n", t);
t = gauge { for(int i=0; i < rpt; i++) { if (has_index(x, elem)) { ; }; } };
werror("has_index() took %fs\n", t);
return 0; }
Sample output on my machine: chromaggus:tools agehall$ pike ~/fun/search_speed.pike 471111 1000000000 Running 1000000000 iterations on array of size 471111 ==-1 took 16.390s <0 took 16.490s has_index() took 16.290s
As you can see, there are no major difference between the three..