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path: root/polymatrix/expression/mixins/divisionexprmixin.py
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from __future__ import annotations

import abc
import dataclasses
import typing

if typing.TYPE_CHECKING:
    from polymatrix.expressionstate.abc import ExpressionState

from polymatrix.expression.mixins.elemmultexprmixin import ElemMultExprMixin
from polymatrix.utils.getstacklines import FrameSummary
from polymatrix.utils.tooperatorexception import to_operator_exception
from polymatrix.polymatrix.init import init_poly_matrix
from polymatrix.expression.mixins.expressionbasemixin import ExpressionBaseMixin
from polymatrix.polymatrix.abc import PolyMatrix


class DivisionExprMixin(ExpressionBaseMixin):
    @property
    @abc.abstractmethod
    def left(self) -> ExpressionBaseMixin: ...

    @property
    @abc.abstractmethod
    def right(self) -> ExpressionBaseMixin: ...

    @property
    @abc.abstractmethod
    def stack(self) -> tuple[FrameSummary]: ...

    # overwrites the abstract method of `ExpressionBaseMixin`
    def apply(
        self,
        state: ExpressionState,
    ) -> tuple[ExpressionState, PolyMatrix]:
        state, left = self.left.apply(state=state)
        state, right = self.right.apply(state=state)

        # if left.shape == (1, 1):
        #     left, right = right, left

        # assert right.shape == (1, 1)

        if not (right.shape == (1, 1)):
            raise AssertionError(
                to_operator_exception(
                    message=f"{right.shape=} is not (1, 1)",
                    stack=self.stack,
                )
            )

        right_poly = right.get_poly(0, 0)

        if len(right_poly) == 1 and tuple() in right_poly:
            right_inv = {(0, 0): {tuple(): 1 / right_poly[tuple()]}}
            return ElemMultExprMixin.elem_mult(
                state=state,
                left=left,
                right=init_poly_matrix(
                    data=right_inv,
                    shape=(1, 1),
                ),
            )

        # add an auxillary equation and, therefore, needs to be cached
        if self in state.cache:
            return state, state.cache[self]

        poly_matrix_data = {}

        division_variable = state.n_param
        state = state.register(n_param=1)

        for row in range(left.shape[0]):
            for col in range(left.shape[1]):
                underlying_poly = left.get_poly(row, col)
                if underlying_poly is None:
                    continue

                def gen_polynomial():
                    for monomial, value in underlying_poly.items():
                        yield monomial + ((division_variable, 1),), value

                poly_matrix_data[row, col] = dict(gen_polynomial())

        def gen_auxillary_polynomials():
            for monomial, value in right_poly.items():
                yield monomial + ((division_variable, 1),), value

        auxillary_poly = dict(gen_auxillary_polynomials())

        if tuple() not in auxillary_poly:
            auxillary_poly[tuple()] = 0

        auxillary_poly[tuple()] -= 1

        poly_matrix = init_poly_matrix(
            data=poly_matrix_data,
            shape=left.shape,
        )

        state = dataclasses.replace(
            state,
            auxillary_equations=state.auxillary_equations
            | {division_variable: auxillary_poly},
            cache=state.cache | {self: poly_matrix},
        )

        return state, poly_matrix