overload permutedims for OneElement matrices (#368)

* overload for OneElement matrices

* add unit test

* more general implementations and unit tests

* make adjustments

* add unit test and style

src/FillArrays.jl

@@ -7,7 +7,7 @@ import Base: size, getindex, setindex!, IndexStyle, checkbounds, convert,
     any, all, axes, isone, iszero, iterate, unique, allunique, permutedims, inv,
     copy, vec, setindex!, count, ==, reshape, map, zero,
     show, view, in, mapreduce, one, reverse, promote_op, promote_rule, repeat,
-    parent, similar, issorted, add_sum, accumulate, OneTo
+    parent, similar, issorted, add_sum, accumulate, OneTo, permutedims
 
 import LinearAlgebra: rank, svdvals!, tril, triu, tril!, triu!, diag, transpose, adjoint, fill!,
     dot, norm2, norm1, normInf, normMinusInf, normp, lmul!, rmul!, diagzero, AdjointAbsVec, TransposeAbsVec,

src/oneelement.jl

@@ -426,6 +426,12 @@ function Base.reshape(A::OneElement, shape::Tuple{Vararg{Int}})
     OneElement(A.val, Tuple(newcartind), shape)
 end
 
+#permute
+_permute(x, p) = ntuple(i -> x[p[i]], length(x))
+permutedims(o::OneElementMatrix) = OneElement(o.val, reverse(o.ind), reverse(o.axes))
+permutedims(o::OneElementVector) = reshape(o, (1, length(o)))
+permutedims(o::OneElement, dims) = OneElement(o.val, _permute(o.ind, dims), _permute(o.axes, dims))
+
 # show
 _maybesize(t::Tuple{Base.OneTo{Int}, Vararg{Base.OneTo{Int}}}) = size.(t,1)
 _maybesize(t) = t

test/runtests.jl

@@ -2667,6 +2667,17 @@ end
         end
     end
 
+    @testset "permutedims" begin
+        v = OneElement(1, (2, 3), (2, 5))
+        @test permutedims(v) === OneElement(1, (3, 2), (5, 2))
+        w = OneElement(1, 3, 5)
+        @test permutedims(w) === OneElement(1, (1, 3), (1, 5))
+        x = OneElement(1, (1, 2, 3), (4, 5, 6))
+        @test permutedims(x, (1, 2, 3)) === x
+        @test permutedims(x, (3, 2, 1)) === OneElement(1, (3, 2, 1), (6, 5, 4))
+        @test permutedims(x, [2, 3, 1]) === OneElement(1, (2, 3, 1), (5, 6, 4))
+        @test_throws BoundsError permutedims(x, (2, 1))
+    end
     @testset "show" begin
         B = OneElement(2, (1, 2), (3, 4))
         @test repr(B) == "OneElement(2, (1, 2), (3, 4))"