feat: add blas/base/izamax

lib/node_modules/@stdlib/blas/base/izamax/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.
+
+-->
+
+# izamax
+
+> Find the index of the first element having maximum |Re(.)| + |Im(.)|.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var izamax = require( '@stdlib/blas/base/izamax' );
+```
+
+#### izamax( N, x, strideX )
+
+Finds the index of the first element having maximum |Re(.)| + |Im(.)|.
+
+```javascript
+var Complex128Array = require( '@stdlib/array/complex128' );
+
+var x = new Complex128Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+
+var idx = izamax( x.length, x, 1 );
+// returns 1
+```
+
+The function has the following parameters:
+
+-   **N**: number of indexed elements.
+-   **x**: input [`Complex128Array`][@stdlib/array/complex128].
+-   **strideX**: index increment for `x`.
+
+The `N` and `strideX` parameters determine which elements in `x` are accessed at runtime. For example, to traverse every other value,
+
+```javascript
+var Complex128Array = require( '@stdlib/array/complex128' );
+
+var x = new Complex128Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+
+var idx = izamax( 2, x, 2 );
+// returns 1
+```
+
+Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
+
+```javascript
+var Complex128Array = require( '@stdlib/array/complex128' );
+
+// Initial array:
+var x0 = new Complex128Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
+
+// Create an offset view:
+var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
+
+// Find index of element having maximum |Re(.)| + |Im(.)|:
+var idx = izamax( 2, x1, 1 );
+// returns 1
+```
+
+#### izamax.ndarray( N, x, strideX, offsetX )
+
+Finds the index of the first element having maximum |Re(.)| + |Im(.)| using alternative indexing semantics.
+
+```javascript
+var Complex128Array = require( '@stdlib/array/complex128' );
+
+var x = new Complex128Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
+
+var idx = izamax.ndarray( x.length, x, 1, 0 );
+// returns 1
+```
+
+The function has the following additional parameters:
+
+-   **offsetX**: starting index.
+
+While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the `offsetX` parameter supports indexing semantics based on a starting index. For example, to start from the second index,
+
+```javascript
+var Complex128Array = require( '@stdlib/array/complex128' );
+
+var x = new Complex128Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0, 7.0, -8.0 ] );
+
+var idx = izamax.ndarray( 3, x, 1, 1 );
+// returns 2
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   If `N < 1`, both functions return `-1`.
+-   `izamax()` corresponds to the [BLAS][blas] level 1 function [`izamax`][izamax].
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
+var filledarrayBy = require( '@stdlib/array/filled-by' );
+var Complex128 = require( '@stdlib/complex/float64/ctor' );
+var izamax = require( '@stdlib/blas/base/izamax' );
+
+function rand() {
+    return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
+}
+
+// Generate random input array:
+var x = filledarrayBy( 10, 'complex128', rand );
+console.log( x.toString() );
+
+var idx = izamax( x.length, x, 1 );
+console.log( idx );
+```
+
+</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/blas/base/izamax.h"
+```
+
+#### c_izamax( N, \*X, strideX )
+
+Finds the index of the first element having maximum |Re(.)| + |Im(.)|.
+
+```c
+const double x[] = { 4.0, 2.0, -3.0, 5.0, -1.0, 2.0 };
+
+CBLAS_INT idx = c_izamax( 3, (void *)x, 1 );
+// returns 1
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **X**: `[in] void*` input array.
+-   **strideX**: `[in] CBLAS_INT` index increment for `X`.
+
+```c
+CBLAS_INT c_izamax( const CBLAS_INT N, const void *X, const CBLAS_INT strideX );
+```
+
+#### c_izamax_ndarray( N, \*X, strideX, offsetX )
+
+Finds the index of the first element having maximum |Re(.)| + |Im(.)| using alternative indexing semantics.
+
+```c
+const double x[] = { 4.0, 2.0, -3.0, 5.0, -1.0, 2.0 };
+
+CBLAS_INT idx = c_izamax_ndarray( 3, (void *)x, 1, 0 );
+// returns 1
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] CBLAS_INT` number of indexed elements.
+-   **X**: `[in] void*` input array.
+-   **strideX**: `[in] CBLAS_INT` index increment for `X`.
+-   **offsetX**: `[in] CBLAS_INT` starting index for `X`.
+
+```c
+CBLAS_INT c_izamax_ndarray( const CBLAS_INT N, const void *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
+```
+
+</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/blas/base/izamax.h"
+#include <stdio.h>
+
+int main( void ) {
+    // Create a strided array:
+    const double x[] = { 1.0, -2.0, 3.0, -4.0, 5.0, -6.0, 7.0, -8.0 };
+
+    // Specify the number of elements:
+    const int N = 4;
+
+    // Specify stride:
+    const int strideX = 1;
+
+    // Compute the index of the maximum value:
+    CBLAS_INT idx = c_izamax( N, (void *)x, strideX );
+
+    // Print the result:
+    printf( "index value: %d\n", idx );
+
+    // Compute the index of the maximum value:
+    idx = c_izamax_ndarray( N, (void *)x, -strideX, N-1 );
+
+    // Print the result:
+    printf( "index value: %d\n", idx );
+}
+```
+
+</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">
+
+[blas]: http://www.netlib.org/blas
+
+[izamax]: https://netlib.org/lapack/explore-html/d0/da5/izamax_8f.html
+
+[@stdlib/array/complex128]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex128
+
+[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
+
+</section>
+
+<!-- /.links -->