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

"""
Computing with MO
"""

from .exceptions import ComputeError
from .add import add
from .minus import minus
from .multiply import multiply

OPERATIONS = {
        "+": add, 
        "-": minus, 
        "*": multiply,
        }

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

    :example:

    >>> from ..MO.mo import MOnumber
    >>> compute("+", MOnumber(1), MOnumber(2))
    <MOnumber 3>
    >>> compute("-", None, MOnumber(2))
    <MOnumber - 2>
    >>> compute("*", MOnumber(1), MOnumber(2))
    <MOnumber 2>
    >>> compute("~", MOnumber(1), MOnumber(2))
    Traceback (most recent call last):
        ...
    mapytex.calculus.core.compute.exceptions.ComputeError: Unknown operation (~)
    """
    try:
        operation = OPERATIONS[node]
    except KeyError:
        raise ComputeError(f"Unknown operation ({node})")

    return operation(left_v, right_v)


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