A cute use of the preprocessor to have this C program:
#include <stdio.h>
#include "haiku.h"
now know summer comes
let us welcome fresh long days
too soon the sun sets
output this haiku:
soon let the sun rise
long nights be banished from us
know now winter ends
Originally inspired by Xavier Leroy's California Codin' and the UCSD CSE haiku craze of 2010.