ref: b4dc52ebf70ffa18e9a7a2b3cee5ff143d8bd5ce 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; }