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Overload Base.literal_pow for AbstractQ #54010

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Merged
merged 3 commits into from
Apr 13, 2024
Merged

Overload Base.literal_pow for AbstractQ #54010

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2c9694f
overload `Base.literal_pow` for `AbstractQ`
dkarrasch Apr 9, 2024
124c010
fix +/-1 exponent
dkarrasch Apr 9, 2024
55702be
follow the matrix case
dkarrasch Apr 9, 2024
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4 changes: 4 additions & 0 deletions stdlib/LinearAlgebra/src/abstractq.jl
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Expand Up @@ -18,6 +18,10 @@ transpose(Q::AbstractQ{<:Real}) = AdjointQ(Q)
transpose(Q::AbstractQ) = error("transpose not implemented for $(typeof(Q)). Consider using adjoint instead of transpose.")
adjoint(adjQ::AdjointQ) = adjQ.Q

(^)(Q::AbstractQ, p::Integer) = p < 0 ? power_by_squaring(inv(Q), -p) : power_by_squaring(Q, p)
@inline Base.literal_pow(::typeof(^), Q::AbstractQ, ::Val{1}) = Q
@inline Base.literal_pow(::typeof(^), Q::AbstractQ, ::Val{-1}) = inv(Q)
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Suggested change
@inline Base.literal_pow(::typeof(^), Q::AbstractQ, ::Val{1}) = Q
@inline Base.literal_pow(::typeof(^), Q::AbstractQ, ::Val{-1}) = inv(Q)

Is there a reason for these? The fallback should work just fine here, no?


# promotion with AbstractMatrix, at least for equal eltypes
promote_rule(::Type{<:AbstractMatrix{T}}, ::Type{<:AbstractQ{T}}) where {T} =
(@inline; Union{AbstractMatrix{T},AbstractQ{T}})
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6 changes: 6 additions & 0 deletions stdlib/LinearAlgebra/test/abstractq.jl
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Expand Up @@ -39,6 +39,12 @@ n = 5
@test Q'*I ≈ Q.Q'*I rtol=2eps(real(T))
@test I*Q ≈ Q.Q*I rtol=2eps(real(T))
@test I*Q' ≈ I*Q.Q' rtol=2eps(real(T))
@test Q^3 ≈ Q*Q*Q
@test Q^2 ≈ Q*Q
@test Q^1 == Q
@test Q^(-1) == Q'
@test (Q')^(-1) == Q
@test (Q')^2 ≈ Q'*Q'
@test abs(det(Q)) ≈ 1
@test logabsdet(Q)[1] ≈ 0 atol=2n*eps(real(T))
y = rand(T, n)
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