8 #define FLOAT_EQUALS_MARGIN 1e-6
10 static bool equal_atoms(struct Atom *atom1, struct Atom *atom2)
15 if (atom1->type != atom2->type) {
19 switch (atom1->type) {
21 return strcmp(atom1->sym, atom2->sym) == 0;
24 return fabsf(atom1->num - atom2->num) <= FLOAT_EQUALS_MARGIN;
27 return strcmp(atom1->str, atom2->str) == 0;
33 static bool equal_cons(struct Cons *cons1, struct Cons *cons2)
37 return equal(cons1->car, cons2->car) && equal(cons1->cdr, cons2->cdr);
40 bool equal(struct Expr obj1, struct Expr obj2)
42 if (obj1.type != obj2.type) {
48 return equal_atoms(obj1.atom, obj2.atom);
51 return equal_cons(obj1.cons, obj2.cons);
60 bool nil_p(struct Expr obj)
63 && strcmp(obj.atom->sym, "nil") == 0;
66 bool symbol_p(struct Expr obj)
68 return obj.type == EXPR_ATOM
69 && obj.atom->type == ATOM_SYMBOL;
72 bool cons_p(struct Expr obj)
74 return obj.type == EXPR_CONS;
77 struct Expr assoc(struct Expr key, struct Expr alist)
79 while (cons_p(alist)) {
80 if (cons_p(alist.cons->car) && equal(alist.cons->car.cons->car, key)) {
81 return alist.cons->car;
84 alist = alist.cons->cdr;
90 struct Expr push(struct Expr newelt, struct Expr place)
93 place.cons->cdr = CONS(place.cons->car, place.cons->cdr);
94 place.cons->car = newelt;