def eval_bin_op(h, l, e):
if is_empty(l):
return None
result = eval_lisp(car(l), e)
l = cdr(l)
while not is_empty(l):
right_operand = eval_lisp(car(l), e)
result = realize_bin_op(get_value(h), result, right_operand)
l = cdr(l)
return result
def eval_cond(l, e):
while not is_empty(l):
cond = car(l)
pred = car(cond)
res = car(cdr(cond))
if pred == 'else':
return eval_lisp(res, e)
if eval_lisp(pred, e):
return eval_lisp(res, e)
l = cdr(l)
return None
def eval_macro(mcr, args, e):
sub_args = mcr.args
se = sub_env(e)
while not is_empty(sub_args):
if is_empty(args):
raise Exception('not enough args!')
arg = car(args)
k = get_value(car(sub_args))
def_env(se, k, arg)
sub_args = cdr(sub_args)
args = cdr(args)
body = macro_expand(mcr.body, se)
return eval_lisp(body, e)
def eval_lambda(lmbd, args, e):
se = sub_env(lmbd.env)
sub_args = lmbd.args
while not is_empty(sub_args):
if is_empty(args):
raise Exception('not enough args!')
arg = eval_lisp(car(args), e)
k = eval_lisp(car(sub_args), se)
def_env(se, k, arg)
sub_args = cdr(sub_args)
args = cdr(args)
body = lmbd.body
return eval_lisp(body, se)
def eval_pred_op(h, l, e):
if is_empty(l):
return None
left_operand = eval_lisp(car(l), e)
l = cdr(l)
result = True
while not is_empty(l):
right_operand = eval_lisp(car(l), e)
result = result and realize_pred_op(get_value(h), left_operand,
right_operand)
if not result:
return False
left_operand = right_operand
l = cdr(l)
return True
def show(l, start_of_list=True):
type = get_type(l)
new_list = True
if type == 'ConsList':
if is_empty(l):
return '()'
if get_type(car(l)) != 'ConsList':
new_list = False
if start_of_list:
return "({} {})".format(show(car(l)), show(cdr(l), new_list))
else:
return "{} {}".format(show(car(l)), show(cdr(l), False))
if type == "<class 'str'>":
return '"{}"'.format(l)
return get_value(l)
def macro_expand(body, e):
type = get_type(body)
if type == 'ConsList':
return cons(macro_expand(car(body), e), macro_expand(cdr(body), e))
if type == 'Symbol':
return eval_symbol(body, e)
return body
def eval_lisp(l, e):
type = get_type(l)
if type == 'ConsList':
if is_empty(l):
return l
head_form = eval_lisp(car(l), e)
tail = cdr(l)
if head_form == OK_symbol:
res = eval_lisp(tail, e)
return res
head_form_type = get_type(head_form)
if head_form_type == 'BinOp':
res = eval_bin_op(head_form, tail, e)
return res
if head_form_type == 'PredOp':
res = eval_pred_op(head_form, tail, e)
return res
if head_form_type == 'SpecialForm':
res = eval_special_form(head_form, tail, e)
return res
if head_form_type == 'Symbol':
res = eval_symbol(head_form, e)
return res
if head_form_type == 'Lambda':
res = eval_lambda(head_form, tail, e)
return res
if head_form_type == 'Macro':
res = eval_macro(head_form, tail, e)
return res
return head_form
if type == 'Symbol':
if get_value(l) == 'None':
return None
return eval_symbol(l, e)
return l
def eval_special_form(h, l, e):
if is_empty(l):
return None
val = get_value(h)
if val == 'def':
t = get_type(car(l))
if t != 'Symbol':
raise Exception('Cant assign to {}. Symbol required.'.format(t))
k = get_value(car(l))
v = eval_lisp(car(cdr(l)), e)
def_env(e, k, v)
elif val == 'defn':
name = car(l)
args = car(cdr(l))
body = car(cdr(cdr(l)))
k = get_value(name)
lmbd = Lambda(args, body, e)
def_env(e, k, lmbd)
elif val == 'lambda':
args = car(l)
body = cdr(l)
return Lambda(args, body, e)
elif val == 'macro':
args = car(l)
body = cdr(l)
return Macro(args, body)
elif val == 'if':
pred = eval_lisp(car(l), e)
t = car(cdr(l))
f = car(cdr(cdr(l)))
if pred:
return eval_lisp(t, e)
else:
return eval_lisp(f, e)
elif val == 'car':
h = car(l)
return eval_lisp(car(eval_lisp(h, e)), e)
elif val == 'cdr':
return cdr(eval_lisp(car(l), e))
elif val == 'cons':
h = eval_lisp(car(l), e)
t = eval_lisp(car(cdr(l)), e)
return cons(h, t)
elif val == '`':
return car(l)
elif val == 'cond':
return eval_cond(l, e)
elif val == 'print':
while not is_empty(l):
r = eval_lisp(car(l), e)
print(r)
l = cdr(l)
return OK_symbol
elif val == 'eval':
a = eval_lisp(car(l), e)
return eval_lisp(a, e)
elif val == 'typeof':
return get_type(car(l))
return OK_symbol
from core import cons, car, cdr
p = cons(3, 4)
r1 = car(p)
r2 = cdr(p)
print("First argument: " + str(r1))
print("Second argument: " + str(r2))
print("Done!")