feat: add ndarray/base/ternary

lib/node_modules/@stdlib/ndarray/base/ternary/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.
+
+-->
+
+# Ternary
+
+> Apply a ternary callback to elements in input ndarrays and assign results to elements in an output ndarray.
+
+<!-- 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 -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var ternary = require( '@stdlib/ndarray/base/ternary' );
+```
+
+#### ternary( arrays, fcn )
+
+Applies a ternary callback to elements in input ndarrays and assigns results to elements in an output ndarray.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var add3 = require( '@stdlib/number/float64/base/add3' );
+
+// Create data buffers:
+var xbuf = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
+var ybuf = new Float64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
+var zbuf = new Float64Array( [ 0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ] );
+var wbuf = new Float64Array( 6 );
+
+// Define the shape of the input and output arrays:
+var shape = [ 3, 1, 2 ];
+
+// Define the array strides:
+var sx = [ 2, 2, 1 ];
+var sy = [ 2, 2, 1 ];
+var sz = [ 2, 2, 1 ];
+var sw = [ 2, 2, 1 ];
+
+// Define the index offsets:
+var ox = 0;
+var oy = 0;
+var oz = 0;
+var ow = 0;
+
+// Create the input and output ndarray-like objects:
+var x = {
+    'dtype': 'float64',
+    'data': xbuf,
+    'shape': shape,
+    'strides': sx,
+    'offset': ox,
+    'order': 'row-major'
+};
+var y = {
+    'dtype': 'float64',
+    'data': ybuf,
+    'shape': shape,
+    'strides': sy,
+    'offset': oy,
+    'order': 'row-major'
+};
+var z = {
+    'dtype': 'float64',
+    'data': zbuf,
+    'shape': shape,
+    'strides': sz,
+    'offset': oz,
+    'order': 'row-major'
+};
+var w = {
+    'dtype': 'float64',
+    'data': wbuf,
+    'shape': shape,
+    'strides': sw,
+    'offset': ow,
+    'order': 'row-major'
+};
+
+// Apply the ternary function:
+ternary( [ x, y, z, w ], add3 );
+
+console.log( w.data );
+// => <Float64Array>[ 2.5, 3.5, 4.5, 5.5, 6.5, 7.5 ]
+```
+
+The function accepts the following arguments:
+
+-   **arrays**: array-like object containing three input ndarrays and one output ndarray.
+-   **fcn**: ternary function to apply.
+
+</section>
+
+<!-- /.usage -->
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+## Notes
+
+
+-   Each provided ndarray should be an object with the following properties:
+
+    -   **dtype**: data type.
+    -   **data**: data buffer.
+    -   **shape**: dimensions.
+    -   **strides**: stride lengths.
+    -   **offset**: index offset.
+    -   **order**: specifies whether an ndarray is row-major (C-style) or column major (Fortran-style).
+
+-   For very high-dimensional ndarrays which are non-contiguous, one should consider copying the underlying data to contiguous memory before applying a ternary function in order to achieve better performance.
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
+var filledarray = require( '@stdlib/array/filled' );
+var filledarrayBy = require( '@stdlib/array/filled-by' );
+var add3 = require( '@stdlib/number/float64/base/add3' );
+var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
+var ndarray2array = require( '@stdlib/ndarray/base/to-array' );
+var ternary = require( '@stdlib/ndarray/base/ternary' );
+
+var N = 10;
+var x = {
+    'dtype': 'generic',
+    'data': filledarrayBy( N, 'generic', discreteUniform( -100, 100 ) ),
+    'shape': [ 5, 2 ],
+    'strides': [ 2, 1 ],
+    'offset': 0,
+    'order': 'row-major'
+};
+console.log( ndarray2array( x.data, x.shape, x.strides, x.offset, x.order ) );
+
+var y = {
+    'dtype': 'generic',
+    'data': filledarrayBy( N, 'generic', discreteUniform( -100, 100 ) ),
+    'shape': x.shape.slice(),
+    'strides': shape2strides( x.shape, 'column-major' ),
+    'offset': 0,
+    'order': 'column-major'
+};
+console.log( ndarray2array( y.data, y.shape, y.strides, y.offset, y.order ) );
+
+var z = {
+    'dtype': 'generic',
+    'data': filledarrayBy( N, 'generic', discreteUniform( -100, 100 ) ),
+    'shape': x.shape.slice(),
+    'strides': shape2strides( x.shape, 'row-major' ),
+    'offset': 0,
+    'order': 'row-major'
+};
+console.log( ndarray2array( z.data, z.shape, z.strides, z.offset, z.order ) );
+
+var w = {
+    'dtype': 'generic',
+    'data': filledarray( 0, N, 'generic' ),
+    'shape': x.shape.slice(),
+    'strides': shape2strides( x.shape, 'column-major' ),
+    'offset': 0,
+    'order': 'column-major'
+};
+
+ternary( [ x, y, z, w ], add3 );
+console.log( ndarray2array( w.data, w.shape, w.strides, w.offset, w.order ) );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- 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 -->