English
PiToModule.fromMatrix maps a matrix A and a vector w to the linear combination ∑_i (A w)_i b_i in M.
Русский
PiToModule.fromMatrix переводит матрицу A и вектор w к линейной комбинации ∑_i (A w)_i b_i в M.
LaTeX
$$PiToModule.fromMatrix_R_b(A,w) = Fintype.linearCombination_R b (A *ᵥ w)$$
Lean4
/-- The composition of a matrix (as an endomorphism of `ι → R`) with the projection
`(ι → R) →ₗ[R] M`. -/
def fromMatrix [DecidableEq ι] : Matrix ι ι R →ₗ[R] (ι → R) →ₗ[R] M :=
(LinearMap.llcomp R _ _ _ (Fintype.linearCombination R b)).comp algEquivMatrix'.symm.toLinearMap