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

"""
Expression

"""
from ..core import Tree, compute, tree2txt, tree2tex



class Expression(object):

    """
    Expression class

    :example:

    >>> e = Expression.from_str("2+3*4")
    >>> e2 = e.simplify()
    >>> print(e2)
    14
    >>> e2.explain()
    '2 + 3 * 4'
    '2 + 12'
    '15'

    """

    RENDER = tree2txt

    def __init__(self, tree):
        """
        """
        self._tree = tree

    @classmethod
    def from_str(cls,  string):
        """ Initiate the expression from a string

        :param string: TODO
        :returns: TODO

        """
        t = Tree.from_str(string)
        return cls(t)

    @classmethod
    def random(self, template, conditions = [], shuffle = False):
        """ Initiate randomly the expression 

        :param template: the template of the expression
        :param conditions: conditions on randomly generate variable
        :param shuffle: allowing to shuffle the tree
        :returns: TODO

        """
        pass

    @classmethod
    def set_render(cls, render):
        """ Define default render function 

        :param render: render function Tree -> str

        :example:
        >>> e = Expression.from_str("2+3*4")
        >>> print(e)
        2 + 3 * 4
        >>> Expression.set_render(tree2tex)
        >>> print(e)
        2 + 3 \\times 4
        """
        cls.RENDER = render

    def __str__(self):
        return self.__class__.RENDER(self._tree)

    def __repr__(self):
        return f"<Tree {self.__class__.RENDER(self._tree)}>"

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