1function C = GB_spec_subassign (C, Mask, accum, A, I, J, descriptor, scalar)
2%GB_SPEC_SUBASSIGN a MATLAB mimic of GxB_subassign
3%
4% Usage:
5% C = GB_spec_subassign (C, Mask, accum, A, I, J, descriptor, scalar)
6%
7% Computes C(I,J)<Mask> = accum(C(I,J),A), in GraphBLAS notation.
8%
9% This function does the same thing as GxB_Matrix_subassign,
10% GxB_Vector_subassign, GxB_Matrix_subassign_TYPE, GxB_Vector_subassign_TYPE,
11% GxB_Row_subassign, and GxB_Col_subassign functions.  In all cases, the Mask
12% is the same size as A (after optionally being transpose) and the submatrix
13% C(I,J).  Entries outside the C(I,J) submatrix are never modified.
14
15% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2021, All Rights Reserved.
16% SPDX-License-Identifier: Apache-2.0
17
18%-------------------------------------------------------------------------------
19% get inputs
20%-------------------------------------------------------------------------------
21
22if (nargout > 1 || nargin ~= 8)
23    error ('usage: C = GB_spec_subassign (C, Mask, accum, A, I, J, descriptor, scalar)') ;
24end
25
26% Convert inputs to dense matrices with explicit patterns and types,
27% and with where X(~X.pattern)==identity for all matrices A, B, and C.
28C = GB_spec_matrix (C) ;
29A = GB_spec_matrix (A) ;
30[C_replace Mask_comp Atrans Btrans Mask_struct] = ...
31    GB_spec_descriptor (descriptor) ;
32Mask = GB_spec_getmask (Mask, Mask_struct) ;
33
34%-------------------------------------------------------------------------------
35
36% apply the descriptor to A
37if (Atrans)
38    A.matrix = A.matrix.' ;
39    A.pattern = A.pattern' ;
40end
41
42% expand I and J if empty
43if (ischar (I) & isempty (I))
44    % I = '' is treated as the empty list
45    I = [ ] ;
46elseif (isempty (I) || isequal (I, ':'))
47    % I = [ ] is treated as ":"
48    nrows = size (C.matrix, 1) ;
49    I = 1:nrows ;
50end
51if (ischar (J) & isempty (J))
52    % J = '' is treated as the empty list
53    J = [ ] ;
54elseif (isempty (J) || isequal (J, ':'))
55    % J = [ ] is treated as the ":"
56    ncols = size (C.matrix, 2) ;
57    J = 1:ncols ;
58end
59
60if (scalar)
61    % scalar expansion: expand A into a matrix
62    ni = length (I) ;
63    nj = length (J) ;
64    A.matrix  (1:ni, 1:nj) = A.matrix (1,1) ;
65    A.pattern (1:ni, 1:nj) = true ;
66end
67
68S.matrix  = C.matrix  (I,J)  ;
69S.pattern = C.pattern (I,J)  ;
70S.class   = C.class  ;
71
72% T = A
73T.matrix  = A.matrix ;
74T.pattern = A.pattern ;
75
76% S<Mask> = accum (S,T): apply the accum, then Mask, and return the result
77S = GB_spec_accum_mask (S, Mask, accum, T, C_replace, Mask_comp, 0) ;
78
79C.matrix  (I,J) = S.matrix  ;
80C.pattern (I,J) = S.pattern  ;
81C.class         = S.class  ;
82
83