Sort ard promotion

Author: Will Tebbutt

src/transform/ardtransform.jl

@@ -37,8 +37,12 @@ dim(t::ARDTransform) = length(t.v)
 
 # Quite specific implementations required to pass correctness and performance tests.
 _map(t::ARDTransform, x::AbstractVector{<:Real}) = x * only(t.v)
-_map(t::ARDTransform, x::ColVecs) = ColVecs((t.v * ones(1, size(x.X, 2))) .* x.X)
-_map(t::ARDTransform, x::RowVecs) = RowVecs(x.X .* (ones(size(x.X, 1)) * collect(t.v')))
+function _map(t::ARDTransform, x::ColVecs)
+    return ColVecs((t.v * ones(eltype(t.v), 1, size(x.X, 2))) .* x.X)
+end
+function _map(t::ARDTransform, x::RowVecs)
+    return RowVecs(x.X .* (ones(eltype(t.v), size(x.X, 1)) * collect(t.v')))
+end
 
 Base.isequal(t::ARDTransform, t2::ARDTransform) = isequal(t.v, t2.v)