Row and Column Iterator for Matrices

stdlib/LinearAlgebra/src/LinearAlgebra.jl

@@ -67,6 +67,7 @@ export
     copyto!,
     copy_transpose!,
     cross,
+    cols,
     adjoint,
     adjoint!,
     det,
@@ -123,6 +124,7 @@ export
     opnorm,
     rank,
     rdiv!,
+    rows,
     schur,
     schur!,
     svd,

stdlib/LinearAlgebra/src/generic.jl

@@ -1415,3 +1415,41 @@ function normalize(v::AbstractVector, p::Real = 2)
         return T[]
     end
 end
+
+# Iterator for the rows() and cols()
+struct MatrixDimIterator{T}
+    row::Bool
+    length::Int
+    M::Matrix{T}
+end
+
+function Base.iterate(it::MatrixDimIterator, state = 1)
+    if state > it.length
+        return nothing
+    elseif it.row == true
+        obj = @view it.M[state, :]
+        return (obj, state+1)
+    else
+        obj = @view it.M[:, state]
+        return (obj, state+1)
+    end
+end
+
+Base.eltype(it::MatrixDimIterator) = it.row == true ? typeof(@view it.M[1, :]) : typeof(@view it.M[:, 1])
+Base.length(it::MatrixDimIterator) = it.length
+"""
+    rows(M::Matrix{T})
+
+Get an iterator for the rows of M.
+See also [`cols`](@ref).
+"""
+rows(M::Matrix) = MatrixDimIterator(true, size(M, 1), M)
+
+
+"""
+    cols(M::Matrix{T})
+
+Get a iterator for the columns of M.
+See also [`rows`](@ref).
+"""
+cols(M::Matrix) = MatrixDimIterator(false, size(M, 2), M)

stdlib/LinearAlgebra/test/generic.jl

@@ -324,6 +324,13 @@ end
     @test_throws ErrorException transpose(rand(2,2,2,2))
 end
 
+
+@testset "rows and columns tests" begin
+    M = [1 2 3; 4 5 6; 7 8 9]
+    @test collect(rows(M)) == [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+    @test collect(cols(M)) == [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+end
+
 @testset "generic functions for checking whether matrices have banded structure" begin
     using LinearAlgebra: isbanded
     pentadiag = [1 2 3; 4 5 6; 7 8 9]