Lisp in 99 Lines of C and How to Write One Yourself

The code is quite lispy, similar to how modern array languages are implemented in Arthur Whitney style C, resembling an array language:

#define L double

L cons(L x,L y) { cell[--sp] = x; cell[--sp] = y; if (hp > sp<<3) abort(); return box(CONS,sp); }
L car(L p) { return (T(p)&~(CONS^CLOS)) == CONS ? cell[ord(p)+1] : err; }
L cdr(L p) { return (T(p)&~(CONS^CLOS)) == CONS ? cell[ord(p)] : err; }

L bind(L v,L t,L e) { return not(v) ? e : T(v) == CONS ? bind(cdr(v),cdr(t),pair(car(v),car(t),e)) : pair(v,t,e);

L reduce(L f,L t,L e) { return eval(cdr(car(f)),bind(car(car(f)),evlis(t,e),not(cdr(f)) ? env : cdr(f))); }