ref: 41fb60c4bc05b9e85c2e4495e15a9b17ba3e8ada 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; }