#! /usr/bin/env python
# -*- coding: utf-8 -*-
# vim:fenc=utf-8
#
# Copyright © 2017 lafrite <lafrite@Poivre>
#
# Distributed under terms of the MIT license.

"""
Evaluating a binary tree
"""

from .operator import OPERATORS

def compute(node, left_v, right_v):
    """ 
    Computing a node 

    :example:

    >>> compute("+", 1, 2)
    3
    >>> compute("-", 1, 2)
    -1
    >>> compute("-", None, 2)
    -2

    """
    op = OPERATORS[node]
    lv = left_v
    rv = right_v
    if lv is None:
        return op["_operate"](rv)()
    
    try:
        return op["operate"](lv)(rv)
    except NotImplemented:
        return op["roperate"](rv)(lv)




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