def eval(self, env):
new_env = Env(env)
# put object in heap
addr = heap.alloc()
heap[addr] = self
for decl in self.decls:
decl.exp.set_this(addr)
decl.eval(new_env)
for key in new_env:
if new_env.directly_defined(key):
self.env[key] = new_env[key]
return addr
