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function C = lt (A, B)
%A < B less than.
% C = (A < B) compares A and B element-by-element. One or
% both may be scalars. Otherwise, A and B must have the same size.
%
% See also GrB/le, GrB/gt, GrB/ge, GrB/ne, GrB/eq.
% The pattern of C depends on the type of inputs:
% A scalar, B scalar: C is scalar.
% A scalar, B matrix: C is full if A<0, otherwise C is a subset of B.
% B scalar, A matrix: C is full if B>0, otherwise C is a subset of A.
% A matrix, B matrix: C has the pattern of the set union, A+B.
% SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
% SPDX-License-Identifier: Apache-2.0
if (isobject (A))
A = A.opaque ;
end
if (isobject (B))
B = B.opaque ;
end
[am, an, atype] = gbsize (A) ;
[bm, bn, btype] = gbsize (B) ;
a_is_scalar = (am == 1) && (an == 1) ;
b_is_scalar = (bm == 1) && (bn == 1) ;
ctype = gboptype (atype, btype) ;
if (a_is_scalar)
if (b_is_scalar)
% both A and B are scalars
C = GrB (gbeunion (A, 0, '<', B, 0)) ;
else
% A is a scalar, B is a matrix
if (gb_scalar (A) < 0)
if (~gb_issigned (btype))
% a < 0, and B has an unsigned type. C is all true.
C = GrB (gb_scalar_to_full (bm, bn, 'logical', ...
gb_fmt (B), true)) ;
else
% since a < 0, entries not present in B result in a true
% value, so the result is full. Expand A to full.
A = gb_scalar_to_full (bm, bn, ctype, gb_fmt (B), A) ;
C = GrB (gbemult (A, '<', gbfull (B, ctype))) ;
end
else
% since a >= 0, entries not present in B result in a false
% value, so the result is a sparse subset of B. select all
% entries in B > a, then convert to true.
C = GrB (gbapply ('1.logical', gbselect (B, '>', A))) ;
end
end
else
if (b_is_scalar)
% A is a matrix, B is a scalar
b = gb_scalar (B) ;
if (b < 0 && ~gb_issigned (atype))
% b is negative, and A has an unsigned type. C is all false.
C = GrB (gbnew (am, an, 'logical')) ;
elseif (b > 0)
% since b > 0, entries not present in A result in a true
% value, so the result is full. Expand B to a full matrix.
B = gb_scalar_to_full (am, an, ctype, gb_fmt (A), B) ;
C = GrB (gbemult (gbfull (A, ctype), '<', B)) ;
else
% since b <= 0, entries not present in A result in a false
% value, so the result is a sparse subset of A. Select all
% entries in A < b, then convert to true.
C = GrB (gbapply ('1.logical', gbselect (A, '<', B))) ;
end
else
% both A and B are matrices. C is the set union of A and B.
C = GrB (gbeunion (A, 0, '<', B, 0)) ;
end
end
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