def op_RAP(self, state):
"""rap works like ap, only that it replaces an occurrence of a
dummy environment with the current one, thus making recursive
functions possible
"""
new_dump = state.D.push(state.S).push(state.E).push(state.C)
closure, new_stack = state.S.pop()
parameters, new_stack = new_stack.pop()
if not isinstance(parameters, Cons):
raise ValueError("top of stack expected to be a cons")
param_list = cons2list(parameters)
new_stack = state.S.reset()
new_env = closure.env.replace_level(param_list)
return SECDState(new_stack, new_env, closure.frame, new_dump)
def op_AP(self, state):
"""ap pops a closure and a list of parameter values from the stack.
The closure is applied to the parameters by installing its
environment as the current one, pushing the parameter list in
front of that, clearing the stack, and setting C to the
closure's function pointer. The previous values of S, E, and
the next value of C are saved on the dump.
"""
new_dump = state.D.push(state.S).push(state.E).push(state.C)
closure, tmp_stack = state.S.pop()
parameters, _ = tmp_stack.pop()
if not isinstance(parameters, Cons):
raise ValueError("top of stack expected to be a cons")
param_list = cons2list(parameters)
new_stack = state.S.reset()
new_env = closure.env.new_level(param_list)
return SECDState(new_stack, new_env, closure.frame, new_dump)
