npm package: @stdlib/strided-base-stride2offset
Description: Determine the index offset which specifies the location of the first indexed value in a strided array.
Author: The Stdlib Authors
Latest version: 0.1.1

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# stride2offset

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> Determine the index offset which specifies the location of the first indexed value in a strided array.

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<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/strided-base-stride2offset
```

</section>

<section class="usage">

## Usage

```javascript
var stride2offset = require( '@stdlib/strided-base-stride2offset' );
```

#### stride2offset( N, stride )

Returns the index offset which specifies the location of the first indexed value in a strided array.

```javascript
var offset = stride2offset( 10, 10 );
// returns 0

offset = stride2offset( 10, -10 );
// returns 90
```

</section>

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<section class="notes">

</section>

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<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var stride2offset = require( '@stdlib/strided-base-stride2offset' );

var opts = {
    'dtype': 'generic'
};

// Define the number of indexed elements:
var N = 100;

// Define a maximum stride length:
var maxStride = 10;

// Create an array of random integers which can accommodate the maximum stride length:
var arr = discreteUniform( N*maxStride, 0, 255, opts );

// Generate random stride lengths:
var strides = discreteUniform( 10, -maxStride, maxStride, opts );

// Resolve values in the data array for the first indexed element based on various stride lengths...
var offset;
var i;
for ( i = 0; i < strides.length; i++ ) {
    offset = stride2offset( N, strides[ i ] );
    console.log( 'stride = %d. arr[%d] = %d.', strides[ i ], offset, arr[ offset ] );
}
```

</section>

<!-- /.examples -->

* * *

<section class="c">

## C APIs

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</section>

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<section class="usage">

### Usage

```c
#include "stdlib/strided/base/stride2offset.h"
```

#### stdlib_strided_stride2offset( N, stride )

Returns the index offset which specifies the location of the first indexed value in a strided array.

```c
#include "stdlib/strided/base/stride2offset.h"
#include <stdint.h>

int64_t offset = stdlib_strided_stride2offset( 10, -10 );
// returns 90
```

The function accepts the following arguments:

-   **N**: `[in] int64_t` number of indexed elements.
-   **stride**: `[in] int64_t` index increment.

```c
int64_t stdlib_strided_stride2offset( int64_t N, int64_t stride );
```

</section>

<!-- /.usage -->

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<section class="notes">

</section>

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<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/strided/base/stride2offset.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

int main( void ) {
    // Specify the number of indexed elements:
    int64_t N = 6;

    // Define a stride:
    int64_t stride = -2;

    // Compute the offset:
    int64_t offset = stdlib_strided_stride2offset( N, stride )

    // Print the results:
    printf( "stride: %"PRId64" => offset: %"PRId64"\n", stride, offset );
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

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## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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