ref: 5c7923fd0f305f45deb57c4d95e94cc1a8dc7cfa dir: /sys/src/ape/lib/ap/gen/abs.c/
#include <stdlib.h> int abs(int a) { if(a < 0) return -a; return a; } long labs(long a) { if(a < 0) return -a; return a; }