def extend(env, variables, values):
if is_pair(variables):
if is_pair(values):
return cons(cons(variables.car, values.car),
extend(env, variables.cdr, values.cdr))
else:
raise ValueError("Too few values")
elif is_null(variables):
if is_null(values):
return env
else:
raise ValueError("Too many values")
elif is_symbol(variables):
return cons(cons(variables, values), env)
else:
raise RuntimeError("Branch should be unreachable")
def __init__(self, *exprs):
super().__init__()
if len(exprs) == 0:
self.exprs = Nil
elif len(exprs) == 1 and is_pair(exprs[0]):
self.exprs = exprs[0]
else:
self.exprs = Nil
for x in exprs[::-1]:
self.exprs = cons(x, self.exprs)
def main():
definitial('x')
defprimitive('+', lambda args: args.car + args.cadr, 2)
defprimitive('-', lambda args: args.car - args.cadr, 2)
defprimitive('<', lambda args: args.car < args.cadr, 2)
defprimitive('cons', lambda args: cons(args.car, args.cadr), 2)
definitial('list', lambda args: args)
definitial('fib', lambda args: args)
while True:
exprs = read() # our version of read returns a list of expressions
for expr in exprs:
value = evaluate(expr, GLOBAL_ENV)
print(value)
def resume(self, vs):
return self.k.resume(cons(self.v, vs))
def test_eval_apply_lambda():
func = LambdaExpr(cons(Symbol("a"), cons(Symbol("b"), Nil)),
cons(ApplyExpr(VariableExpr(Symbol("+")), cons(VariableExpr(Symbol("a")), cons(VariableExpr(Symbol("b")), Nil))), Nil))
expr = ApplyExpr(func, cons(QuoteExpr(5), cons(QuoteExpr(2), Nil)))
expr.evaluate(GLOBAL_ENV, AssertEqCont(7))
def test_eval_apply_primitive():
expr = ApplyExpr(VariableExpr(Symbol("+")), cons(QuoteExpr(1), cons(QuoteExpr(2), Nil)))
expr.evaluate(GLOBAL_ENV, AssertEqCont(3))
def test_eval_lambda():
expr = LambdaExpr(cons(Symbol("a"), cons(Symbol("b"), Nil)),
cons(QuoteExpr(42), Nil))
expr.evaluate(NullEnv(), AssertInstanceCont(Function))
def test_eval_begin():
expr = BeginExpr(QuoteExpr(1), QuoteExpr(2), QuoteExpr(3))
expr.evaluate(NullEnv(), AssertEqCont(3))
expr = BeginExpr(cons(QuoteExpr(1), cons(QuoteExpr(2), cons(QuoteExpr(3), Nil))))
expr.evaluate(NullEnv(), AssertEqCont(3))
def primitive(name, value, vs, arity, k):
if arity == length(vs):
return k.resume(value(vs))
else:
raise TypeError("incorrect arity {} {}".format(name, vs))
GLOBAL_ENV = NullEnv()
definitial('f')
definitial('foo')
definitial('bar')
definitial('x')
definitial('y')
definitial('z')
defprimitive('null?', lambda args: is_null(args.car), 1)
defprimitive('cons', lambda args: cons(args.car, args.cadr), 2)
defprimitive('car', lambda args: args.caar, 1)
defprimitive('cdr', lambda args: args.cdar, 1)
defprimitive('+', lambda args: args.car + args.cadr, 2)
defprimitive('-', lambda args: args.car - args.cadr, 2)
defprimitive('*', lambda args: args.car * args.cadr, 2)
defprimitive('/', lambda args: args.car / args.cadr, 2)
definitial('println', Primitive('println', lambda args, r, k: k.resume(
print() if is_null(args) else print(str(args)[1:-1]))))
definitial(
'call/cc',
Primitive(
'call/cc',
lambda vs, r, k: vs.car.invoke(cons(k, Nil), r, k) if length(
vs) == 1 else wrong(
def primitive(name, value, vs, arity, k):
if arity == length(vs):
return k.resume(value(vs))
else:
raise TypeError("incorrect arity {} {}".format(name, vs))
GLOBAL_ENV = NullEnv()
definitial('f')
definitial('foo')
definitial('bar')
definitial('x')
definitial('y')
definitial('z')
defprimitive('null?', lambda args: is_null(args.car), 1)
defprimitive('cons', lambda args: cons(args.car, args.cadr), 2)
defprimitive('car', lambda args: args.caar, 1)
defprimitive('cdr', lambda args: args.cdar, 1)
defprimitive('+', lambda args: args.car + args.cadr, 2)
defprimitive('-', lambda args: args.car - args.cadr, 2)
defprimitive('*', lambda args: args.car * args.cadr, 2)
defprimitive('/', lambda args: args.car / args.cadr, 2)
definitial(
'println',
Primitive(
'println', lambda args, r, k: k.resume(print()
if is_null(args) else print(
str(args)[1:-1]))))
definitial(
'call/cc',
def definitial(name, value=None):
global GLOBAL_ENV
GLOBAL_ENV = cons(cons(name, value), GLOBAL_ENV)
return name
def evlis(exps, env):
if is_pair(exps):
argument = evaluate(exps.car, env)
return cons(argument, evlis(exps.cdr, env))
else:
return Nil
def primitive(name, value, vs, arity, k):
if arity == length(vs):
return k.resume(value(vs))
else:
raise TypeError("incorrect arity {} {}".format(name, vs))
GLOBAL_ENV = NullEnv()
definitial('f')
definitial('foo')
definitial('bar')
definitial('x')
definitial('y')
definitial('z')
defprimitive('null?', lambda args: is_null(args.car), 1)
defprimitive('cons', lambda args: cons(args.car, args.cadr), 2)
defprimitive('car', lambda args: args.caar, 1)
defprimitive('cdr', lambda args: args.cdar, 1)
defprimitive('+', lambda args: args.car + args.cadr, 2)
defprimitive('-', lambda args: args.car - args.cadr, 2)
defprimitive('*', lambda args: args.car * args.cadr, 2)
defprimitive('/', lambda args: args.car / args.cadr, 2)
definitial(
'println',
Primitive(
'println', lambda args, r, k: k.resume(print()
if is_null(args) else print(
str(args)[1:-1]))))
# ========================================================================
# begin exercise-specific code
