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Original file line number Diff line number Diff line change
@@ -0,0 +1,147 @@
<!--
@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.
-->

# glastIndexLessThan

> Return the index of the last element in a one-dimensional ndarray which is less than a corresponding element in another one-dimensional ndarray.
<section class="intro">

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var glastIndexLessThan = require( '@stdlib/blas/ext/base/ndarray/glast-index-less-than' );
```

#### glastIndexLessThan( arrays )

Returns the index of the last element in a one-dimensional ndarray which is less than a corresponding element in another one-dimensional ndarray.

```javascript
var vector = require( '@stdlib/ndarray/vector/ctor' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );

var x = vector( [ 0.0, 0.0, 0.0, 0.0 ], 'generic' );
var y = vector( [ 0.0, 0.0, 1.0, 0.0 ], 'generic' );

var fromIndex = scalar2ndarray( 3, {
'dtype': 'generic'
});

var idx = glastIndexLessThan( [ x, y, fromIndex ] );
// returns 2
```

The function has the following parameters:

- **arrays**: array-like object containing the following ndarrays:

- first one-dimensional input ndarray.
- second one-dimensional input ndarray.
- a zero-dimensional ndarray containing the index from which to begin searching.

If the function is unable to find an element in the first one-dimensional input ndarray which is less than a corresponding element in the second one-dimensional input ndarray, the function returns `-1`.

```javascript
var vector = require( '@stdlib/ndarray/vector/ctor' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );

var x = vector( [ 5.0, 6.0, 7.0, 8.0 ], 'generic' );
var y = vector( [ 1.0, 2.0, 3.0, 4.0 ], 'generic' );

var fromIndex = scalar2ndarray( 3, {
'dtype': 'generic'
});

var idx = glastIndexLessThan( [ x, y, fromIndex ] );
// returns -1
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

- If a specified starting search index is negative, the function resolves the starting search index by counting backward from the last element (where `-1` refers to the last element).
- When comparing elements, the function checks whether an element in the first one-dimensional input ndarray is less than a corresponding element in the second one-dimensional input ndarray using the less-than operator `<`. As a consequence, comparisons involving `NaN` always evaluate to `false`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random/discrete-uniform' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var ndarraylike2scalar = require( '@stdlib/ndarray/ndarraylike2scalar' );
var glastIndexLessThan = require( '@stdlib/blas/ext/base/ndarray/glast-index-less-than' );

var opts = {
'dtype': 'generic'
};
var x = discreteUniform( [ 10 ], 0, 10, opts );
console.log( ndarray2array( x ) );

var y = discreteUniform( [ 10 ], 0, 10, opts );
console.log( ndarray2array( y ) );

var fromIndex = scalar2ndarray( 9, {
'dtype': 'generic'
});
console.log( 'From Index:', ndarraylike2scalar( fromIndex ) );

var idx = glastIndexLessThan( [ x, y, fromIndex ] );
console.log( idx );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

</section>

<!-- /.links -->
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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 bench = require( '@stdlib/bench' );
var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
var pow = require( '@stdlib/math/base/special/pow' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
var ones = require( '@stdlib/ndarray/ones' );
var format = require( '@stdlib/string/format' );
var pkg = require( './../package.json' ).name;
var glastIndexLessThan = require( './../lib' );


// VARIABLES //

var options = {
'dtype': 'generic'
};


// FUNCTIONS //

/**
* Creates a benchmark function.
*
* @private
* @param {PositiveInteger} len - array length
* @returns {Function} benchmark function
*/
function createBenchmark( len ) {
var fromIndex;
var x;
var y;

x = ones( [ len ], options );
y = ones( [ len ], options );
fromIndex = scalar2ndarray( len - 1, {
'dtype': 'generic'
});
return benchmark;

/**
* Benchmark function.
*
* @private
* @param {Benchmark} b - benchmark instance
*/
function benchmark( b ) {
var out;
var i;

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
out = glastIndexLessThan( [ x, y, fromIndex ] );
if ( out !== out ) {
b.fail( 'should return an integer' );
}
}
b.toc();
if ( !isInteger( out ) ) {
b.fail( 'should return an integer' );
}
b.pass( 'benchmark finished' );
b.end();
}
}


// MAIN //

/**
* Main execution sequence.
*
* @private
*/
function main() {
var len;
var min;
var max;
var f;
var i;

min = 1; // 10^min
max = 6; // 10^max

for ( i = min; i <= max; i++ ) {
len = pow( 10, i );
f = createBenchmark( len );
bench( format( '%s:len=%d', pkg, len ), f );
}
}

main();
Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@

{{alias}}( arrays )
Returns the index of the last element in a one-dimensional ndarray which is
less than a corresponding element in another one-dimensional ndarray.

If a specified starting search index is negative, the function resolves the
starting search index by counting backward from the last element (where `-1`
refers to the last element).

When comparing elements, the function checks whether an element in the first
one-dimensional input ndarray is less than a corresponding element in the
second one-dimensional input ndarray using the less-than operator `<`. As a
consequence, comparisons involving `NaN` always evaluate to `false`.

Parameters
----------
arrays: ArrayLikeObject<ndarray>
Array-like object containing the following ndarrays:

- first one-dimensional input ndarray.
- second one-dimensional input ndarray.
- a zero-dimensional ndarray containing the index from which to begin
searching.

Returns
-------
out: integer
Index.

Examples
--------
> var x = {{alias:@stdlib/ndarray/vector/ctor}}( [ 0.0, 0.0, 0.0, 0.0 ], 'generic' );
> var y = {{alias:@stdlib/ndarray/vector/ctor}}( [ 0.0, 0.0, 1.0, 0.0 ], 'generic' );
> var i = {{alias:@stdlib/ndarray/from-scalar}}( 3, { 'dtype': 'generic' } );
> {{alias}}( [ x, y, i ] )
2

See Also
--------
Original file line number Diff line number Diff line change
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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.
*/

// TypeScript Version: 4.1

/// <reference types="@stdlib/types"/>

import { typedndarray } from '@stdlib/types/ndarray';

/**
* Returns the index of the last element in a one-dimensional ndarray which is less than a corresponding element in another one-dimensional ndarray.
*
* ## Notes
*
* - The function expects the following ndarrays:
*
* - first one-dimensional input ndarray.
* - second one-dimensional input ndarray.
* - a zero-dimensional ndarray containing the index from which to begin searching.
*
* - When comparing elements, the function checks whether an element in the first one-dimensional input ndarray is less than a corresponding element in the second one-dimensional input ndarray using the less-than operator `<`. As a consequence, comparisons involving `NaN` always evaluate to `false`.
*
* @param arrays - array-like object containing ndarrays
* @returns index
*
* @example
* var vector = require( '@stdlib/ndarray/vector/ctor' );
* var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
*
* var x = vector( [ 0.0, 0.0, 0.0, 0.0 ], 'generic' );
* var y = vector( [ 0.0, 0.0, 1.0, 0.0 ], 'generic' );
*
* var fromIndex = scalar2ndarray( 3, {
* 'dtype': 'generic'
* });
*
* var idx = glastIndexLessThan( [ x, y, fromIndex ] );
* // returns 2
*/
declare function glastIndexLessThan( arrays: [ typedndarray<unknown>, typedndarray<unknown>, typedndarray<number> ] ): number;


// EXPORTS //

export = glastIndexLessThan;
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