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Fix elementary Matrix construction bug #1372

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Fix elementary Matrix construction bug #1372

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13 changes: 7 additions & 6 deletions lib/Value/Matrix.pm
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Original file line number Diff line number Diff line change
Expand Up @@ -1081,7 +1081,7 @@ Usage:
generates the matrix

[ [ 1, 0, 0, 0 ],
[ 0, 4, 0, 0 ],
[ 0, 3, 0, 0 ],
[ 0, 0, 1, 0 ],
[ 0, 0, 0, 1 ] ]

Expand All @@ -1102,15 +1102,16 @@ Usage:
generates the matrix:

[ [ 1, 0, 0, 0 ],
[ 0, 1, 0, 0 ],
[ 0, -3, 1, 0 ],
[ 0, 1, -3, 0 ],
[ 0, 0, 1, 0 ],
[ 0, 0, 0, 1 ] ]

or if the matrix C<$A> exists then
or if the matrix C<$A> exists of size m by n then

$A->E([3, 4], -5);

will generate the elementary matrix of size number of rows of C<$A>, which multiplies row 3 by -5 and adds to row 4.
will generate the m by m elementary matrix which multiplies row 3 by -5 and adds to row 4.
If $A does not have at least 4 rows, an error is raised.

=back

Expand Down Expand Up @@ -1147,7 +1148,7 @@ sub E {
if (@ij == 1) {
$row[$i] = $k if ($i == $ij[0]);
} elsif (defined $k) {
$row[ $ij[1] ] = $k if ($i == $ij[0]);
$row[ $ij[0] ] = $k if ($i == $ij[1]);
} else {
($row[ $ij[0] ], $row[ $ij[1] ]) = ($row[ $ij[1] ], $row[ $ij[0] ]) if ($i == $ij[0] || $i == $ij[1]);
}
Expand Down
15 changes: 14 additions & 1 deletion t/math_objects/matrix.t
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Expand Up @@ -357,8 +357,21 @@ subtest 'Construct an elementary matrix' => sub {
'Elementary Matrix with row multiple';

my $E3 = Value::Matrix->E(4, [ 3, 2 ], -3);
is $E3->TeX, Matrix([ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, -3, 1, 0 ], [ 0, 0, 0, 1 ] ])->TeX,
is $E3->TeX, Matrix([ [ 1, 0, 0, 0 ], [ 0, 1, -3, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ])->TeX,
'Elementary Matrix with row multiple and add';

my $A = Matrix([ [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ], [ 9, 10, 11, 12 ], [ 13, 14, 15, 16 ] ]);
is $A->E([ 1, 4 ])->TeX,
Matrix([ [ 0, 0, 0, 1 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 1, 0, 0, 0 ] ])->TeX,
'Elementary Matrix from syntax $A->E an existing matrix with a row swap';

is $A->E([2], 5)->TeX,
Matrix([ [ 1, 0, 0, 0 ], [ 0, 5, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ])->TeX,
'Elementary Matrix from syntax $A->E an existing matrix with a row multiple';

is $A->E([ 2, 4 ], -4)->TeX,
Matrix([ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, -4, 0, 1 ] ])->TeX,
'Elementary Matrix from syntax $A->E an existing matrix with a row multiple and add';
};

subtest 'Extract a slice from a Matrix' => sub {
Expand Down