ref: b2e29cf3158d6e8c6a0263cb1bbb06e72a21f7fb 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; }