Add back support for null space

Author: mtfishman

src/fillarrays/matrixalgebrakit.jl

@@ -148,3 +148,19 @@ for f in [:left_orth!, :right_orth!]
     end
   end
 end
+
+for f in [:left_null!, :right_null!]
+  _f = Symbol(:_, f)
+  @eval begin
+    function _initialize_output(::typeof($f), a::Eye)
+      return a
+    end
+    function $_f(a::Eye, F)
+      return F
+    end
+
+    function MatrixAlgebraKit.$f(a::EyeEye, F; kwargs...)
+      return throw(MethodError($f, (a, F)))
+    end
+  end
+end

src/matrixalgebrakit.jl

@@ -180,13 +180,17 @@ for f in [:left_orth!, :right_orth!]
 end
 
 for f in [:left_null!, :right_null!]
+  _f = Symbol(:_, f)
   @eval begin
     function MatrixAlgebraKit.initialize_output(::typeof($f), a::KroneckerMatrix)
       return _initialize_output($f, a.a) ⊗ _initialize_output($f, a.b)
     end
+    function $_f(a::AbstractMatrix, F; kwargs...)
+      return $f(a, F; kwargs...)
+    end
     function MatrixAlgebraKit.$f(a::KroneckerMatrix, F; kwargs1=(;), kwargs2=(;), kwargs...)
-      $f(a.a, F.a; kwargs..., kwargs1...)
-      $f(a.b, F.b; kwargs..., kwargs2...)
+      $_f(a.a, F.a; kwargs..., kwargs1...)
+      $_f(a.b, F.b; kwargs..., kwargs2...)
       return F
     end
   end

test/test_fillarrays_matrixalgebrakit.jl

@@ -245,31 +245,31 @@ herm(a) = parent(hermitianpart(a))
     @test arguments(d, 2) isa Ones{real(elt)}
   end
 
-  ## # left_null
-  ## a = Eye(3, 3) ⊗ randn(3, 3)
-  ## n = @constinferred left_null(a)
-  ## @test norm(n' * a) ≈ 0
-  ## @test arguments(n, 1) isa Eye
+  # left_null
+  a = Eye(3, 3) ⊗ randn(3, 3)
+  n = @constinferred left_null(a)
+  @test norm(n' * a) ≈ 0
+  @test arguments(n, 1) isa Eye
 
-  ## a = randn(3, 3) ⊗ Eye(3, 3)
-  ## n = @constinferred left_null(a)
-  ## @test norm(n' * a) ≈ 0
-  ## @test arguments(n, 2) isa Eye
+  a = randn(3, 3) ⊗ Eye(3, 3)
+  n = @constinferred left_null(a)
+  @test norm(n' * a) ≈ 0
+  @test arguments(n, 2) isa Eye
 
-  ## a = Eye(3) ⊗ Eye(3)
-  ## @test_throws MethodError left_null(a)
+  a = Eye(3) ⊗ Eye(3)
+  @test_throws MethodError left_null(a)
 
-  ## # right_null
-  ## a = Eye(3) ⊗ randn(3, 3)
-  ## n = @constinferred right_null(a)
-  ## @test norm(a * n') ≈ 0
-  ## @test arguments(n, 1) isa Eye
+  # right_null
+  a = Eye(3) ⊗ randn(3, 3)
+  n = @constinferred right_null(a)
+  @test norm(a * n') ≈ 0
+  @test arguments(n, 1) isa Eye
 
-  ## a = randn(3, 3) ⊗ Eye(3)
-  ## n = @constinferred right_null(a)
-  ## @test norm(a * n') ≈ 0
-  ## @test arguments(n, 2) isa Eye
+  a = randn(3, 3) ⊗ Eye(3)
+  n = @constinferred right_null(a)
+  @test norm(a * n') ≈ 0
+  @test arguments(n, 2) isa Eye
 
-  ## a = Eye(3) ⊗ Eye(3)
-  ## @test_throws MethodError right_null(a)
+  a = Eye(3) ⊗ Eye(3)
+  @test_throws MethodError right_null(a)
 end