Python-symbolic/python_symb/TreeModification/basic_modif.py

from python_symb.Expressions.expr import Expr
from python_symb.MathTypes.symbols import Var
from python_symb.MathTypes.operator_file import Operator, BinOperator, Add, Mul, Exp
from typing import Union


Number = Union[int, float]


def expand(expr: Expr) -> Expr:

    """
    Expand an expression

    :param expr: expression to expand
    :return: expanded expression

    example :
    5*(a+b) -> 5*a + 5*b
    Expr(Mul, [5, Expr(Add, [Expr(a), Expr(b)])]) -> Expr(Add, [Expr(Mul, [5, Expr(a)]), Expr(Mul, [5, Expr(b)])])
    """

    if expr.is_leaf:
        return expr

    match expr:

        case Expr(BinOperator() as Op1, [Expr(BinOperator() as Op2, op2_children), right]) if Op2.name in Op1.properties.left_distributive:
            expanded_right = expand(right)
            return expand(Expr(Op2, [Expr(Op1, [op2_child, expanded_right]) for op2_child in op2_children]))

        case Expr(BinOperator() as Op1, [left, Expr(BinOperator() as Op2, op2_children)]) if Op2.name in Op1.properties.right_distributive:
            expanded_left = expand(left)
            return expand(Expr(Op2, [Expr(Op1, [expanded_left, op2_child]) for op2_child in op2_children]))

        case Expr(BinOperator() as Op, [left, right]):
            left_leaf, right_leaf = left.is_leaf, right.is_leaf
            if not left_leaf:
                left = expand(left)
            if not right_leaf:
                right = expand(right)
            return Expr(Op, [left, right])

    return expr


def _regroup(expr: Expr, focus_op: BinOperator) -> Expr:
    """
    regroup an expression, with the contraint that the value of expr is focus_op
    Will be used to regroup an expression

    :param expr: expression to regroup
    :param focus_op: operator to regroup
    :return
    x+x+x+x -> 4*x
    Expr(Add, [Expr(x), Expr(Add, [Expr(x), Expr(Add, [Expr(x), Expr(x)])])]) -> Expr(Mul, [4, Expr(x)])

    with Mul == Add.repeated_op
    """
    assert focus_op.repeated_op is not None, f'{focus_op} has no repeated_op'
    assert expr.value == focus_op, f'{expr.value} is not a {focus_op}'

    # Motifs : Key : (Expr) -> Value : int
    # represent number of times the expression appears in the expression,
    # custom expr hash make for instance x+y and y+x the same when counting in motifs
    motifs = {}

    def collect_motifs(expr: Expr):
        match expr:
            case Expr(BinOperator() as op, [left, right]) if op == focus_op:
                collect_motifs(left)
                collect_motifs(right)
            case Expr(BinOperator() as op, [left, right]) if op == focus_op.repeated_op and isinstance(right.value, Number):
                motifs[left] = motifs.get(expr, 0) + right.value
            case Expr(BinOperator() as op, [left, right]) if op == focus_op.repeated_op and op.properties.commutative and isinstance(left.value, Number):

                motifs[right] = 1 if right not in motifs else motifs[right] + left.value

            case _:
                motifs[expr] = 1 if expr not in motifs else motifs[expr] + 1

    collect_motifs(expr)
    tuple_motifs = list(motifs.items())

    def reconstruct(tuple_motifs):
        match tuple_motifs:
            case [(expr, int(a))]:
                if a == focus_op.repeated_op.properties.neutral_element:
                    return expr
                elif focus_op.repeated_op.properties.commutative:
                    return Expr(focus_op.repeated_op, [Expr(a), expr])
                return Expr(focus_op.repeated_op, [expr, Expr(a)])

            case [(expr, int(a)), *rest]:
                if a == focus_op.repeated_op.properties.neutral_element:
                    return Expr(focus_op, [expr, reconstruct(rest)])
                elif focus_op.repeated_op.properties.commutative:
                    return Expr(focus_op, [Expr(focus_op.repeated_op, [Expr(a), expr]), reconstruct(rest)])
                return Expr(focus_op, [Expr(focus_op.repeated_op, [expr, Expr(a)]), reconstruct(rest)])

    return reconstruct(tuple_motifs)

def regroup(expr: Expr, focus_op: BinOperator) -> Expr:
    """
    Regroup an expression

    :param expr: expression to regroup
    :param focus_op: operator to regroup
    :return: regrouped expression

    example :
    x+x+x+x -> 4*x
    Expr(Add, [Expr(x), Expr(Add, [Expr(x), Expr(Add, [Expr(x), Expr(x)])])]) -> Expr(Mul, [4, Expr(x)])
    """

    if expr.is_leaf:
        return expr

    match expr:
        case Expr(BinOperator() as op, [left, right]) if op == focus_op:
            return _regroup(expr, focus_op)

        case Expr(BinOperator() as op, [left, right]):
            return Expr(op, [regroup(left, focus_op), regroup(right, focus_op)])

    return expr


def ungroup(expr: Expr, focus_op: BinOperator) -> Expr:
    """
    Ungroup an expression

    :param expr: expression to ungroup
    :param focus_op: operator to ungroup

    exemple :
    with focus_op = Exp
    (x+y) ^ 2 -> (x+y)*(x+y)
    """

    def recreate(expr: Expr, nb_repeat: int) -> Expr:
        if nb_repeat == 1:
            return expr
        return Expr(focus_op.deconstruct_op, [expr, recreate(expr, nb_repeat-1)])

    if expr.is_leaf:
        return expr

    match expr:
        case Expr(BinOperator() as op, [left, leaf]) if op == focus_op and isinstance(leaf.value, int):
            return recreate(ungroup(left, focus_op), leaf.value)
        case Expr(BinOperator() as op, [leaf, right]) if op == focus_op and isinstance(leaf.value, int):
            return recreate(ungroup(right, focus_op), leaf.value)
        case Expr(BinOperator() as op, [left, right]):
            return Expr(op, [ungroup(left, focus_op), ungroup(right, focus_op)])

    return expr