add intersect for CartesianIndices

fixes JuliaLang#33055
stev47 · Jul 14, 2020 · 90ee4a6 · 90ee4a6
1 parent 5f2bb1d
commit 90ee4a6
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diff --git a/base/multidimensional.jl b/base/multidimensional.jl
@@ -479,6 +479,10 @@ module IteratorsMD
 
     Base.LinearIndices(inds::CartesianIndices{N,R}) where {N,R} = LinearIndices{N,R}(inds.indices)
 
+    # array operations
+    Base.intersect(a::CartesianIndices{N}, b::CartesianIndices{N}) where N =
+        CartesianIndices(intersect.(a.indices, b.indices))
+
     # Views of reshaped CartesianIndices are used for partitions — ensure these are fast
     const CartesianPartition{T<:CartesianIndex, P<:CartesianIndices, R<:ReshapedArray{T,1,P}} = SubArray{T,1,R,Tuple{UnitRange{Int}},false}
     eltype(::Type{PartitionIterator{T}}) where {T<:ReshapedArrayLF} = SubArray{eltype(T), 1, T, Tuple{UnitRange{Int}}, true}

diff --git a/test/cartesian.jl b/test/cartesian.jl
@@ -67,4 +67,9 @@ end
     @test iterate(I, CartesianIndex(4, typemax(Int)))    === nothing
 end
 
+@testset "CartesianIndices operations" begin
+    I = CartesianIndices((1:3, 4:6))
+    J = CartesianIndices((2:4, 3:5))
 
+    @test @inferred(intersect(I, J)) == CartesianIndices((2:3, 4:5))
+end