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# cindexOf

> Return the first index of a specified search element in a single-precision complex floating-point strided array.

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</section>

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<section class="usage">

## Usage

```javascript
var cindexOf = require( '@stdlib/blas/ext/base/cindex-of' );
```

#### cindexOf( N, searchElement, x, strideX )

Returns the first index of a specified search element in a single-precision complex floating-point strided array.

```javascript
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var idx = cindexOf( x.length, new Complex64( 3.0, 4.0 ), x, 1 );
// returns 1
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **searchElement**: search element ([`Complex64`][@stdlib/complex/float32/ctor]).
-   **x**: input [`Complex64Array`][@stdlib/array/complex64].
-   **strideX**: stride length.

If the function is unable to find a search element, the function returns `-1`.

```javascript
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var idx = cindexOf( x.length, new Complex64( 7.0, 8.0 ), x, 1 );
// returns -1
```

The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to search every other element:

```javascript
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

var idx = cindexOf( 2, new Complex64( 5.0, 6.0 ), 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 Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

// Initial array...
var x0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

// Create an offset view...
var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Find index...
var idx = cindexOf( 3, new Complex64( 7.0, 8.0 ), x1, 1 );
// returns 2
```

#### cindexOf.ndarray( N, searchElement, x, strideX, offsetX )

Returns the first index of a specified search element in a single-precision complex floating-point strided array using alternative indexing semantics.

```javascript
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

var idx = cindexOf.ndarray( x.length, new Complex64( 3.0, 4.0 ), 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 offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements of the strided array

```javascript
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

var idx = cindexOf.ndarray( 3, new Complex64( 5.0, 6.0 ), x, 1, x.length-3 );
// returns 1
```

</section>

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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   When searching for a search element, the function checks for equality of the real and imaginary components using the strict equality operator `===`. As a consequence, `NaN` values are considered distinct, and `-0` and `+0` are considered the same.

</section>

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<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var uniform = require( '@stdlib/random/array/uniform' );
var Complex64Array = require( '@stdlib/array/complex64' );
var Complex64 = require( '@stdlib/complex/float32/ctor' );
var cindexOf = require( '@stdlib/blas/ext/base/cindex-of' );

var buf = uniform( 10*2, -10, 10, {
    'dtype': 'float32'
});
var x = new Complex64Array( buf.buffer );
console.log( x );

var idx = cindexOf( x.length, new Complex64( 5.0, 5.0 ), x, 1 );
console.log( idx );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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</section>

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<section class="usage">

### Usage

```c
#include "stdlib/blas/ext/base/cindex_of.h"
```

#### stdlib_strided_cindex_of( N, searchElement, \*X, strideX )

Returns the first index of a specified search element in a single-precision complex floating-point strided array.

```c
#include "stdlib/complex/float32/ctor.h"

const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
const stdlib_complex64_t searchElement = stdlib_complex64( 3.0f, 4.0f );

int idx = stdlib_strided_cindex_of( 3, searchElement, (const stdlib_complex64_t *)x, 1 );
// returns 1
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **searchElement**: `[in] stdlib_complex64_t` search element.
-   **X**: `[in] stdlib_complex64_t*` input array.
-   **strideX**: `[in] CBLAS_INT` stride length.

```c
CBLAS_INT stdlib_strided_cindex_of( const CBLAS_INT N, const stdlib_complex64_t searchElement, const stdlib_complex64_t *X, const CBLAS_INT strideX );
```

#### stdlib_strided_cindex_of_ndarray( N, searchElement, \*X, strideX, offsetX )

Returns the first index of a specified search element in a single-precision complex floating-point strided array using alternative indexing semantics.

```c
#include "stdlib/complex/float32/ctor.h"

const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
const stdlib_complex64_t searchElement = stdlib_complex64( 3.0f, 4.0f );

int idx = stdlib_strided_cindex_of_ndarray( 3, searchElement, (const stdlib_complex64_t *)x, 1, 0 );
// returns 1
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **searchElement**: `[in] stdlib_complex64_t` search element.
-   **X**: `[in] stdlib_complex64_t*` input array.
-   **strideX**: `[in] CBLAS_INT` stride length.
-   **offsetX**: `[in] CBLAS_INT` starting index.

```c
CBLAS_INT stdlib_strided_cindex_of_ndarray( const CBLAS_INT N, const stdlib_complex64_t searchElement, const stdlib_complex64_t *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
```

</section>

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</section>

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<section class="examples">

### Examples

```c
#include "stdlib/blas/ext/base/cindex_of.h"
#include "stdlib/complex/float32/ctor.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array (interleaved real and imaginary components):
    const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };

    // Specify the number of indexed elements:
    const int N = 4;

    // Specify a stride:
    const int strideX = 1;

    // Specify a search element:
    const stdlib_complex64_t searchElement = stdlib_complex64( 5.0f, 6.0f );

    // Perform a search:
    int idx = stdlib_strided_cindex_of( N, searchElement, (const stdlib_complex64_t *)x, strideX );

    // Print the result:
    printf( "index value: %d\n", idx );
}
```

</section>

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</section>

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</section>

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<section class="links">

[@stdlib/array/complex64]: https://www.npmjs.com/package/@stdlib/array-complex64

[@stdlib/complex/float32/ctor]: https://www.npmjs.com/package/@stdlib/complex-float32-ctor

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

</section>

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