Subspaces.jl provides a Subspace type for representing linear subspaces of a finite dimensional vector space. Subspaces of matrices or tensors are also supported, as these are vectors in the mathematical sense of the word. Both real and complex base fields are supported.
julia> using Subspaces
julia> S = Subspace([ [1,0,0], [0,1,1] ])
Subspace{Float64} size (3,) dim 2
julia> [1,2,2] ∈ S
true
julia> [1,1,2] ∈ S
false
julia> S.basis
3×2 Array{Float64,2}:
0.0 1.0
-0.707107 0.0
-0.707107 0.0
julia> S | Subspace([ [0,0,1] ])
Subspace{Float64} size (3,) dim 3
julia> S & Subspace([ [1,1,1] ])
Subspace{Float64} size (3,) dim 1
julia> kron(S, S)
Subspace{Float64} size (9,) dim 4
julia> S * S'
Subspace{Float64} size (3, 3) dim 4
julia> Subspace([ ones(3,4,5) ])
Subspace{Float64} size (3, 4, 5) dim 1