def visit_App(self, node):
m1 = self.visit(node.left_exp)
if not isinstance(m1, Lambda):
raise TypeError
m2 = self.visit(node.right_exp)
sub = Substitution(m2, m1.var)
return self.visit(sub.subst(m1.exp))
def visit_App(self, node):
m1 = node.left_exp
m2 = node.right_exp
try:
return App(self.visit(m1), m2)
except Stuck:
if not isinstance(m1, Lambda):
raise TypeError
try:
return App(m1, self.visit(m2))
except Stuck:
sub = Substitution(m2, m1.var)
return sub.subst(m1.exp)
def visit_LetIn(self, node):
sub = Substitution(self.visit(node.exp), node.var)
return self.visit(sub.subst(node.body))
def visit_LetIn(self, node):
try:
return LetIn(node.var, self.visit(node.exp), node.body)
except Stuck:
sub = Substitution(node.exp, node.var)
return sub.subst(node.body)
