add LowerTriangular, UpperTriangular and Diagonal functions to interface

Author: abhinavmehndiratta

src/Interface/Interface.jl

@@ -12,6 +12,6 @@ import SuiteSparseGraphBLAS:
 include("./Object_Methods/Matrix_Methods.jl")
 include("./Object_Methods/Vector_Methods.jl")
 include("./Object_Methods/Descriptor_Methods.jl")
-export findnz, nnz
+export findnz, nnz, LowerTriangular, UpperTriangular, Diagonal
 
 end # end of module

src/Interface/Object_Methods/Matrix_Methods.jl

@@ -303,3 +303,45 @@ function copy(A::GrB_Matrix{T}) where T <: valid_types
     end
     return C
 end
+
+"""
+    LowerTriangular(A)
+
+Return lower triangle of a GraphBLAS matrix.
+"""
+function LowerTriangular(A::GrB_Matrix{T}) where T <: valid_types 
+    nrows, ncols = size(A)
+    if nrows != ncols
+        error("Matrix is not square")
+    end
+    L = GrB_Matrix(T, nrows, ncols)
+    GxB_select(L, GrB_NULL, GrB_NULL, GxB_TRIL, A, 0, GrB_NULL)
+    return L
+end
+
+"""
+    UpperTriangular(A)
+
+Return upper triangle of a GraphBLAS matrix.
+"""
+function UpperTriangular(A::GrB_Matrix{T}) where T <: valid_types 
+    nrows, ncols = size(A)
+    if nrows != ncols
+        error("Matrix is not square")
+    end
+    U = GrB_Matrix(T, nrows, ncols)
+    GxB_select(U, GrB_NULL, GrB_NULL, GxB_TRIU, A, 0, GrB_NULL)
+    return U
+end
+
+"""
+    Diagonal(A)
+
+Return diagonal of a GraphBLAS matrix.
+"""
+function Diagonal(A::GrB_Matrix{T}) where T <: valid_types 
+    nrows, ncols = size(A)
+    D = GrB_Matrix(T, nrows, ncols)
+    GxB_select(D, GrB_NULL, GrB_NULL, GxB_DIAG, A, 0, GrB_NULL)
+    return D
+end

src/Operations/Select.jl

@@ -44,4 +44,4 @@ function GxB_Matrix_select(             # C<Mask> = accum (C, op(A,k)) or op(A',
                         C.p, Mask.p, accum.p, op.p, A.p, Ref(thunk), desc.p
                     )
                 )
-end
+end

src/SuiteSparseGraphBLAS.jl

@@ -170,7 +170,7 @@ include("Interface/Interface.jl")
 
 using .Interface
 
-export findnz, nnz
+export findnz, nnz, LowerTriangular, UpperTriangular, Diagonal
 
 export
 # Context Methods