feat: add number/int64/base/identity

lib/node_modules/@stdlib/number/int64/base/identity/README.md

@@ -0,0 +1,218 @@
+<!--
+
+@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.
+
+-->
+
+# Identity Function
+
+> Evaluate the [identity function][identity-function] for a 64-bit signed integer.
+
+<section class="intro">
+
+The [identity function][identity-function] is defined as
+
+<!-- <equation class="equation" label="eq:identity_function" align="center" raw="f(x) = x" alt="Identity function"> -->
+
+```math
+f(x) = x
+```
+
+<!-- </equation> -->
+
+for all `x`.
+
+</section>
+
+<!-- /.intro -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var identity = require( '@stdlib/number/int64/base/identity' );
+```
+
+#### identity( x )
+
+Evaluates the [identity function][identity-function] for a 64-bit signed integer.
+
+```javascript
+var Int64 = require( '@stdlib/number/int64/ctor' );
+
+var x = new Int64( 1 );
+var v = identity( x );
+// returns <Int64>[ 1n ]
+
+x = new Int64( 0 );
+v = identity( x );
+// returns <Int64>[ 0n ]
+
+x = new Int64( 4294967296 );
+v = identity( x );
+// returns <Int64>[ 4294967296n ]
+
+x = new Int64( -1000000000000 );
+v = identity( x );
+// returns <Int64>[ -1000000000000n ]
+```
+
+The function accepts the following arguments:
+
+-   **x**: `Int64` input value.
+
+</section>
+
+<!-- /.usage -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
+var logEachMap = require( '@stdlib/console/log-each-map' );
+var Int64 = require( '@stdlib/number/int64/ctor' );
+var identity = require( '@stdlib/number/int64/base/identity' );
+
+// Create an array of random 64-bit signed integers:
+var x = [];
+var i;
+for ( i = 0; i < 10; i++ ) {
+    x.push( new Int64( discreteUniform( -500, 500 ) ) );
+}
+
+// Perform element-wise operation:
+logEachMap( 'identity(%s) = %s', x, identity );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- C usage documentation. -->
+
+<section class="usage">
+
+### Usage
+
+```c
+#include "stdlib/number/int64/base/identity.h"
+```
+
+#### stdlib_base_int64_identity( x )
+
+Evaluates the identity function for a 64-bit signed integer.
+
+```c
+#include <stdint.h>
+
+int64_t y = stdlib_base_int64_identity( 2 );
+// returns 2
+```
+
+The function accepts the following arguments:
+
+-   **x**: `[in] int64_t` input value.
+
+```c
+int64_t stdlib_base_int64_identity( const int64_t x );
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- C API usage examples. -->
+
+<section class="examples">
+
+### Examples
+
+```c
+#include "stdlib/number/int64/base/identity.h"
+#include <stdio.h>
+#include <stdint.h>
+
+int main( void ) {
+    const int64_t x[] = { 3, 5, 10, 4294967296 };
+
+    int64_t y;
+    int i;
+    for ( i = 0; i < 4; i++ ) {
+        y = stdlib_base_int64_identity( x[ i ] );
+        printf( "f(%ld) = %ld\n", x[ i ], y );
+    }
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
+<!-- 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">
+
+[identity-function]: https://en.wikipedia.org/wiki/Identity_function
+
+<!-- <related-links> -->
+
+<!-- </related-links> -->
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/number/int64/base/identity/benchmark/benchmark.js

@@ -0,0 +1,57 @@
+/**
+* @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 discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var getHighWord = require( '@stdlib/number/int64/base/get-high-word' );
+var Int64 = require( '@stdlib/number/int64/ctor' );
+var pkg = require( './../package.json' ).name;
+var identity = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var x;
+	var y;
+	var i;
+
+	x = [];
+	for ( i = 0; i < 100; i++ ) {
+		x.push( new Int64( discreteUniform( -500, 500 ) ) );
+	}
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		y = identity( x[ i%x.length ] );
+		if ( typeof y !== 'object' ) {
+			b.fail( 'should return an Int64 instance' );
+		}
+	}
+	b.toc();
+	if ( isnan( getHighWord( y ) ) ) {
+		b.fail( 'should not return NaN' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});

lib/node_modules/@stdlib/number/int64/base/identity/benchmark/benchmark.native.js

@@ -0,0 +1,67 @@
+/**
+* @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 resolve = require( 'path' ).resolve;
+var bench = require( '@stdlib/bench' );
+var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var Int64 = require( '@stdlib/number/int64/ctor' );
+var getHighWord = require( '@stdlib/number/int64/base/get-high-word' );
+var tryRequire = require( '@stdlib/utils/try-require' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+
+
+// VARIABLES //
+
+var identity = tryRequire( resolve( __dirname, './../lib/native.js' ) );
+var opts = {
+	'skip': ( identity instanceof Error )
+};
+
+
+// MAIN //
+
+bench( format( '%s::native', pkg ), opts, function benchmark( b ) {
+	var x;
+	var y;
+	var i;
+
+	x = [];
+	for ( i = 0; i < 100; i++ ) {
+		x.push( new Int64( discreteUniform( -500, 500 ) ) );
+	}
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		y = identity( x[ i%x.length ] );
+		if ( typeof y !== 'object' ) {
+			b.fail( 'should return an Int64 instance' );
+		}
+	}
+	b.toc();
+	if ( isnan( getHighWord( y ) ) ) {
+		b.fail( 'should not return NaN' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});