#include "Boolean.h" Boolean *trueConstant; Boolean *falseConstant; @implementation Boolean + (void) initialize { trueConstant = [Boolean new]; [trueConstant retain]; falseConstant = [Boolean new]; [falseConstant retain]; } + (id) trueConstant { return trueConstant; } + (id) falseConstant { return falseConstant; } - (string) printForm { return self == trueConstant ? "#t" : "#f"; } @end