#!/usr/bin/env python
# -*- encoding: utf-8 -*-
#
# Copyright (c) 2015 ASMlover. All rights reserved.
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# modification, are permitted provided that the following conditions
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from eLisp.model import Symbol, EmptyList
from eLisp.expr.util import (
        is_tagged_list, cons, cdr, cadr, cddr, caar, cadar)

def is_let_binding(expr):
    return is_tagged_list(expr, Symbol('set'))

def binding_variables(expr):
    def inner(expr):
        if expr is EmptyList:
            return EmptyList
        return cons(caar(expr), inner(cdr(expr)))

    return inner(cadr(expr))

def binding_values(expr):
    def inner(expr):
        if expr is EmptyList:
            return EmptyList
        return cons(cadar(expr), inner(cdr(expr)))

    return inner(cadr(expr))

def binding_body(expr):
    return cddr(expr)

add binding expression