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* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
var gany = require( '@stdlib/blas/ext/base/gany' ).ndarray;
var isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major' );
var accessors = require( './accessors.js' );
// MAIN //
/**
* Returns the index of the first column in an input matrix which contains at least one truthy element.
*
* ## Notes
*
* - If the function is provided an empty matrix or if the function is unable to find a column with at least one truthy element, the function returns `-1` (i.e., an invalid index).
*
* @param {PositiveInteger} M - number of rows in `A`
* @param {PositiveInteger} N - number of columns in `A`
* @param {Collection} A - input matrix
* @param {integer} strideA1 - stride length for the first dimension of `A`
* @param {integer} strideA2 - stride length for the second dimension of `A`
* @param {NonNegativeInteger} offsetA - starting index for `A`
* @returns {integer} column index
*
* @example
* var A = [ 0.0, 1.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 0.0 ]; // => [ [ 0.0, 1.0, 1.0, 0.0 ], [ 0.0, 0.0, 1.0, 0.0 ], [ 0.0, 1.0, 1.0, 0.0 ], [ 0.0, 1.0, 1.0, 0.0 ] ]
*
* var out = gindexOfTruthyColumn( 4, 4, A, 4, 1, 0 );
* // returns 1
*
* @example
* var A = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]; // => [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 0.0, 0.0 ] ]
*
* var out = gindexOfTruthyColumn( 2, 4, A, 4, 1, 0 );
* // returns -1
*
* @example
* var A = [ 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 0.0 ]; // => [ [ 0.0, 0.0, 1.0, 0.0 ], [ 0.0, 1.0, 1.0, 0.0 ] ]
*
* var out = gindexOfTruthyColumn( 2, 4, A, 4, 1, 0 );
* // returns 1
*/
function gindexOfTruthyColumn( M, N, A, strideA1, strideA2, offsetA ) {
var ia;
var j;
var i;
var k;
var o;
// Check whether the matrix is an empty matrix...
if ( M <= 0 || N <= 0 ) {
return -1;
}
// Column-major: iterate down columns
if ( isColumnMajor( [ strideA1, strideA2 ] ) ) {
ia = offsetA;
for ( j = 0; j < N; j++ ) {
if ( gany( M, A, strideA1, ia ) ) {
return j;
}
ia += strideA2;
}
return -1;
}
// Row-major: iterate across rows
o = arraylike2object( A );
if ( o.accessorProtocol ) {
return accessors( M, N, o, strideA1, strideA2, offsetA );
}
j = N;
for ( i = 0; i < M; i++ ) {
ia = offsetA + ( i*strideA1 );
for ( k = 0; k < j; k++ ) {
if ( A[ ia ] ) {
j = k;
break;
}
ia += strideA2;
}
if ( j === 0 ) {
return 0;
}
}
if ( j < N ) {
return j;
}
return -1;
}
// EXPORTS //
module.exports = gindexOfTruthyColumn;
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