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Original file line number Diff line number Diff line change
@@ -0,0 +1,134 @@
<!--

@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.

-->

# gleftPadEdge

> Prepend elements to a one-dimensional output ndarray by repeating the leading edge element of a one-dimensional input ndarray.

<section class="intro">

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var gleftPadEdge = require( '@stdlib/blas/ext/base/ndarray/gleft-pad-edge' );
```

#### gleftPadEdge( arrays )

Prepends elements to a one-dimensional output ndarray by repeating the leading edge element of a one-dimensional input ndarray.

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

var x = vector( [ 1.0, 2.0, 3.0, 4.0 ], 'generic' );
var y = zeros( [ 10 ], {
'dtype': 'generic'
});

var k = scalar2ndarray( 6, {
'dtype': 'generic'
});

var out = gleftPadEdge( [ x, y, k ] );
// returns <ndarray>[ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 2.0, 3.0, 4.0 ]

var bool = ( out === y );
// returns true
```

The function has the following parameters:

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

- a one-dimensional input ndarray.
- a one-dimensional output ndarray.
- a zero-dimensional ndarray specifying the number of elements to pad.

</section>

<!-- /.usage -->

<section class="notes">

## Notes

- If the input ndarray is empty, the function returns the output ndarray unchanged.
- If `k < 0`, the function clamps `k` to `0`, such that indexed elements in `x` are copied to `y` without padding.

</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 zeros = require( '@stdlib/ndarray/zeros' );
var gleftPadEdge = require( '@stdlib/blas/ext/base/ndarray/gleft-pad-edge' );

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

var x = discreteUniform( [ 10 ], -100, 100, opts );
console.log( ndarray2array( x ) );

var k = scalar2ndarray( 5, opts );

var y = zeros( [ 15 ], opts );
console.log( ndarray2array( y ) );

var v = gleftPadEdge( [ x, y, k ] );
console.log( ndarray2array( v ) );
```

</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 -->
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.
*/

'use strict';

// MODULES //

var bench = require( '@stdlib/bench' );
var uniform = require( '@stdlib/random/uniform' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var pow = require( '@stdlib/math/base/special/pow' );
var zeros = require( '@stdlib/ndarray/zeros' );
var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
var format = require( '@stdlib/string/format' );
var pkg = require( './../package.json' ).name;
var gleftPadEdge = 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 x;
var y;
var k;

x = uniform( [ len ], 0.0, 100.0, options );
y = zeros( [ len+5 ], options );
k = scalar2ndarray( 5, options );

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 = gleftPadEdge( [ x, y, k ] );
if ( typeof out !== 'object' ) {
b.fail( 'should return an ndarray' );
}
}
b.toc();
if ( isnan( out.get( i%( len+5 ) ) ) ) {
b.fail( 'should not return NaN' );
}
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 +1,37 @@

{{alias}}( arrays )
Prepends elements to a one-dimensional output ndarray by repeating the
leading edge element of a one-dimensional input ndarray.

If the input ndarray is empty, the function returns the output ndarray
unchanged.

If `k < 0`, the function clamps `k` to `0`, such that indexed elements in
`x` are copied to `y` without padding.

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

- a one-dimensional input ndarray.
- a one-dimensional output ndarray.
- a zero-dimensional ndarray specifying the number of elements to pad.

Returns
-------
out: ndarray
Output ndarray.

Examples
--------
> var opts = { 'dtype': 'generic' };
> var x = {{alias:@stdlib/ndarray/vector/ctor}}( [ 1.0, 2.0, 3.0, 4.0 ], opts.dtype );
> var y = {{alias:@stdlib/ndarray/zeros}}( [ 10 ], opts );
> var k = {{alias:@stdlib/ndarray/from-scalar}}( 6, opts );
> {{alias}}( [ x, y, k ] )
<ndarray>[ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 2.0, 3.0, 4.0 ]

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';

/**
* Prepends elements to a one-dimensional output ndarray by repeating the leading edge element of a one-dimensional input ndarray.

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Similar to #15422 (comment), I think we should change to

Suggested change
* Prepends elements to a one-dimensional output ndarray by repeating the leading edge element of a one-dimensional input ndarray.
* Prepends elements to a one-dimensional input ndarray by repeating the leading edge element and writes the results to a one-dimensional output ndarray.

*
* ## Notes
*
* - The function expects the following ndarrays:
*
* - a one-dimensional input ndarray.
* - a one-dimensional output ndarray.
* - a zero-dimensional ndarray specifying the number of elements to pad.
*
* @param arrays - array-like object containing ndarrays
* @returns output ndarray
*
* @example
* var vector = require( '@stdlib/ndarray/vector/ctor' );
* var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
* var zeros = require( '@stdlib/ndarray/zeros' );
*
* var x = vector( [ 1.0, 2.0, 3.0, 4.0 ], 'generic' );
* var y = zeros( [ 10 ], {
* 'dtype': 'generic'
* });
*
* var k = scalar2ndarray( 6, {
* 'dtype': 'generic'
* });
*
* var out = gleftPadEdge( [ x, y, k ] );
* // returns <ndarray>[ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 2.0, 3.0, 4.0 ]
*/
declare function gleftPadEdge<T extends typedndarray<number> = typedndarray<number>>( arrays: [ typedndarray<number>, T, typedndarray<number> ] ): T;

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// EXPORTS //

export = gleftPadEdge;
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