7 #define FLOAT_EQUALS_MARGIN 1e-6
9 static bool equal_atoms(struct Atom *atom1, struct Atom *atom2)
14 if (atom1->type != atom2->type) {
18 switch (atom1->type) {
20 return strcmp(atom1->sym, atom2->sym) == 0;
23 return fabsf(atom1->num - atom2->num) <= FLOAT_EQUALS_MARGIN;
26 return strcmp(atom1->str, atom2->str) == 0;
32 static bool equal_cons(struct Cons *cons1, struct Cons *cons2)
36 return equal(cons1->car, cons2->car) && equal(cons1->cdr, cons2->cdr);
39 bool equal(struct Expr obj1, struct Expr obj2)
41 if (obj1.type != obj2.type) {
47 return equal_atoms(obj1.atom, obj2.atom);
50 return equal_cons(obj1.cons, obj2.cons);
59 bool nil_p(struct Expr obj)
61 return obj.type == EXPR_ATOM
62 && obj.atom->type == ATOM_SYMBOL
63 && strcmp(obj.atom->sym, "nil");
66 struct Expr assoc(struct Expr key, struct Expr alist)
68 /* TODO: assoc has a recursive implementation */
72 switch (alist.cons->car.type) {
74 if (equal(alist.cons->car.cons->car, key)) {
75 return alist.cons->car;
77 return assoc(key, alist.cons->cdr);
82 return assoc(key, alist.cons->cdr);