time-to-botec/squiggle/node_modules/@stdlib/strided/napi/dmap/README.md

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# dmap

> C API for registering a Node-API module exporting a strided array interface for applying a unary callback accepting and returning double-precision floating-point numbers to each element in a double-precision floating-point strided input array and assigning results to elements in a double-precision floating-point strided output array.

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## Usage

```javascript
var headerDir = require( '@stdlib/strided/napi/dmap' );
```

#### headerDir

Absolute file path for the directory containing header files for C APIs.

```javascript
var dir = headerDir;
// returns <string>
```

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## Examples

```javascript
var headerDir = require( '@stdlib/strided/napi/dmap' );

console.log( headerDir );
// => <string>
```

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* * *

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## C APIs

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### Usage

```c
#include "stdlib/strided/napi/dmap.h"
```

#### stdlib_strided_napi_dmap( env, info, fcn )

Invokes a strided array interface which applies a unary callback accepting and returning double-precision floating-point numbers to each element in a double-precision floating-point strided input array and assigns results to elements in a double-precision floating-point strided output array.

```c
#include <node_api.h>

// ...

static double identity( const double x ) {
    return x;
}

// ...

/**
* Receives JavaScript callback invocation data.
*
* @param env    environment under which the function is invoked
* @param info   callback data
* @return       Node-API value
*/
napi_value addon( napi_env env, napi_callback_info info ) {
    stdlib_strided_napi_dmap( env, info, identity );
    return NULL;
}

// ...
```

The function accepts the following arguments:

-   **env**: `[in] napi_env` environment under which the function is invoked.
-   **info**: `[in] napi_callback_info` callback data.
-   **fcn**: `[in] double (*fcn)( double )` unary callback.

```c
void stdlib_strided_napi_dmap( napi_env env, napi_callback_info info, double (*fcn)( double ) );
```

#### STDLIB_STRIDED_NAPI_MODULE_DMAP( clbk )

Macro for registering a Node-API module exporting a strided array interface for applying a unary callback accepting and return double-precision floating-point numbers to each element in a double-precision floating-point strided input array and assigning results to elements in a double-precision floating-point strided output array.

```c
static double scale( const double x ) {
    return x * 10.0;
}

// ...

// Register a Node-API module:
STDLIB_STRIDED_NAPI_MODULE_DMAP( scale );
```

The macro expects the following arguments:

-   **clbk**: `double (*fcn)( double )` unary callback.

When used, this macro should be used **instead of** `NAPI_MODULE`. The macro includes `NAPI_MODULE`, thus ensuring Node-API module registration.

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### Notes

-   The function expects that the callback `info` argument provides access to the following JavaScript arguments:

    -   `N`: number of indexed elements.
    -   `X`: input [`Float64Array`][@stdlib/array/float64].
    -   `strideX`: `X` stride length.
    -   `Y`: destination [`Float64Array`][@stdlib/array/float64].
    -   `strideY`: `Y` stride length.

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[@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64

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