ref: 8d8b64cd2cd5141a3957d8fb24f7b5ea61db6eda 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; }