ref: 07c8c2c838256ea0b3b9dd6d5a70ba32ff3bafab 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; }