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path: root/polymatrix/expression/mixins/blockdiagexprmixin.py
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import abc
import itertools
import dataclassabc
from polymatrix.polymatrix.mixins import PolyMatrixMixin

from polymatrix.expression.mixins.expressionbasemixin import ExpressionBaseMixin
from polymatrix.polymatrix.abc import PolyMatrix
from polymatrix.expressionstate.abc import ExpressionState


class BlockDiagExprMixin(ExpressionBaseMixin):
    @property
    @abc.abstractmethod
    def underlying(self) -> tuple[ExpressionBaseMixin, ...]:
        ...

    # overwrites the abstract method of `ExpressionBaseMixin`
    def apply(
        self, 
        state: ExpressionState,
    ) -> tuple[ExpressionState, PolyMatrix]:
    
        all_underlying = []
        for expr in self.underlying:
            state, polymat = expr.apply(state=state)
            all_underlying.append(polymat)

        @dataclassabc.dataclassabc(frozen=True)
        class BlockDiagPolyMatrix(PolyMatrixMixin):
            all_underlying: tuple[PolyMatrixMixin]
            underlying_row_col_range: tuple[tuple[int, int], ...]
            shape: tuple[int, int]

            def get_poly(self, row: int, col: int) -> dict[tuple[int, ...], float]:

                for polymatrix, ((row_start, col_start), (row_end, col_end)) in zip(self.all_underlying, self.underlying_row_col_range):
                    if row_start <= row < row_end:
                        if col_start <= col < col_end:
                            return polymatrix.get_poly(
                                row=row-row_start,
                                col=col-col_start,
                            )

                        else:
                            return None

                raise Exception(f'row {row} is out of bounds')

        underlying_row_col_range = tuple(itertools.pairwise(
            itertools.accumulate(
                (expr.shape for expr in all_underlying), 
                lambda acc, v: tuple(v1+v2 for v1, v2 in zip(acc, v)),
                initial=(0, 0))
        ))

        shape = underlying_row_col_range[-1][1]

        polymatrix = BlockDiagPolyMatrix(
            all_underlying=all_underlying,
            shape=shape,
            underlying_row_col_range=underlying_row_col_range,
        )

        return state, polymatrix