feat: add blas/ext/base/ndarray/dtril

lib/node_modules/@stdlib/blas/ext/base/ndarray/dtril/README.md

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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.
+
+-->
+
+# dtril
+
+> Copy the lower triangular part of a double-precision floating-point matrix `A` to another matrix `B`.
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var dtril = require( '@stdlib/blas/ext/base/ndarray/dtril' );
+```
+
+#### dtril( arrays )
+
+Copies the lower triangular part of a double-precision floating-point matrix `A` to another matrix `B`.
+
+```javascript
+var Float64Matrix = require( '@stdlib/ndarray/matrix/float64' );
+var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
+
+var A = new Float64Matrix( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
+var B = new Float64Matrix( [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] );
+
+var k = scalar2ndarray( 0, {
+    'dtype': 'generic'
+});
+
+var out = dtril( [ A, B, k ] );
+// returns <ndarray>[ [ 1.0, 0.0 ], [ 3.0, 4.0 ] ]
+
+var bool = ( out === B );
+// returns true
+```
+
+The function has the following parameters:
+
+-   **arrays**: array-like object containing the following ndarrays:
+
+    -   a two-dimensional input ndarray corresponding to `A`.
+    -   a two-dimensional output ndarray corresponding to `B`.
+    -   a zero-dimensional ndarray specifying the diagonal above which to ignore. A value equal to zero refers to the main diagonal, greater than zero refers to a diagonal above the main diagonal, and less than zero refers to a diagonal below the main diagonal.
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   Elements outside of the copied region are left unchanged.
+
+</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 dtril = require( '@stdlib/blas/ext/base/ndarray/dtril' );
+
+var opts = {
+    'dtype': 'float64'
+};
+
+var A = discreteUniform( [ 5, 5 ], -50, 50, opts );
+console.log( ndarray2array( A ) );
+
+var B = discreteUniform( [ 5, 5 ], -50, 50, opts );
+console.log( ndarray2array( B ) );
+
+var k = scalar2ndarray( 0, {
+    'dtype': 'generic'
+});
+
+var out = dtril( [ A, B, k ] );
+console.log( ndarray2array( out ) );
+```
+
+</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 -->

lib/node_modules/@stdlib/blas/ext/base/ndarray/dtril/benchmark/benchmark.js

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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 format = require( '@stdlib/string/format' );
+var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
+var pkg = require( './../package.json' ).name;
+var dtril = require( './../lib' );
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var A = uniform( [ len, len ], -100.0, 100.0, options );
+	var B = uniform( [ len, len ], -100.0, 100.0, options );
+
+	var k = scalar2ndarray( 0, {
+		'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 = dtril( [ A, B, k ] );
+			if ( typeof out !== 'object' ) {
+				b.fail( 'should return an ndarray' );
+			}
+		}
+		b.toc();
+		if ( isnan( out.get( i%len, i%len ) ) ) {
+			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 = 3; // 10^max
+
+	for ( i = min; i <= max; i++ ) {
+		len = pow( 10, i );
+		f = createBenchmark( len );
+		bench( format( '%s:len=%d', pkg, len ), f );
+	}
+}
+
+main();

lib/node_modules/@stdlib/blas/ext/base/ndarray/dtril/docs/repl.txt

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+
+{{alias}}( arrays )
+    Copies the lower triangular part of a double-precision floating-point matrix
+    `A` to another matrix `B`.
+
+    The diagonal parameter `k` specifies the diagonal above which to ignore. A
+    value of `k = 0` refers to the main diagonal, `k > 0` refers to a diagonal
+    above the main diagonal, and `k < 0` refers to a diagonal below the main
+    diagonal.
+
+    Parameters
+    ----------
+    arrays: ArrayLikeObject<ndarray>
+        Array-like object containing the following ndarrays:
+
+        - a two-dimensional input ndarray corresponding to `A`.
+        - a two-dimensional output ndarray corresponding to `B`.
+        - a zero-dimensional ndarray specifying the diagonal above which to
+        ignore.
+
+    Returns
+    -------
+    out: ndarray
+        Output ndarray.
+
+    Examples
+    --------
+    > var abuf = [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ];
+    > var A = new {{alias:@stdlib/ndarray/matrix/float64}}( abuf );
+
+    > var bbuf = [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ];
+    > var B = new {{alias:@stdlib/ndarray/matrix/float64}}( bbuf );
+
+    > var k = {{alias:@stdlib/ndarray/from-scalar}}( 0, { 'dtype': 'generic' } );
+
+    > {{alias}}( [ A, B, k ] );
+    > B
+    <ndarray>[ [ 1.0, 0.0 ], [ 3.0, 4.0 ] ]
+
+    See Also
+    --------
+

lib/node_modules/@stdlib/blas/ext/base/ndarray/dtril/docs/types/index.d.ts

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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 { float64ndarray, typedndarray } from '@stdlib/types/ndarray';
+
+/**
+* Copies the lower triangular part of a double-precision floating-point matrix `A` to another matrix `B`.
+*
+* ## Notes
+*
+* -   The function expects the following ndarrays:
+*
+*     -   a two-dimensional input ndarray corresponding to `A`.
+*     -   a two-dimensional output ndarray corresponding to `B`.
+*     -   a zero-dimensional ndarray specifying the diagonal above which to ignore.
+*
+* @param arrays - array-like object containing ndarrays
+* @returns output ndarray
+*
+* @example
+* var Float64Matrix = require( '@stdlib/ndarray/matrix/float64' );
+* var scalar2ndarray = require( '@stdlib/ndarray/from-scalar' );
+*
+* var A = new Float64Matrix( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
+* var B = new Float64Matrix( [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] );
+*
+* var k = scalar2ndarray( 0, {
+*     'dtype': 'generic'
+* });
+*
+* var out = dtril( [ A, B, k ] );
+* // returns <ndarray>[ [ 1.0, 0.0 ], [ 3.0, 4.0 ] ]
+*
+* var bool = ( out === B );
+* // returns true
+*/
+declare function dtril( arrays: [ float64ndarray, float64ndarray, typedndarray<number> ] ): float64ndarray;
+
+
+// EXPORTS //
+
+export = dtril;