# smap
> C API for registering a Node-API module exporting a strided array interface for applying a unary callback accepting and returning single-precision floating-point numbers to each element in a single-precision floating-point strided input array and assigning results to elements in a single-precision floating-point strided output array.
## Usage
```javascript
var headerDir = require( '@stdlib/strided/napi/smap' );
```
#### headerDir
Absolute file path for the directory containing header files for C APIs.
```javascript
var dir = headerDir;
// returns
```
## Examples
```javascript
var headerDir = require( '@stdlib/strided/napi/smap' );
console.log( headerDir );
// =>
```
* * *
## C APIs
### Usage
```c
#include "stdlib/strided/napi/smap.h"
```
#### stdlib_strided_napi_smap( env, info, fcn )
Invokes a strided array interface which applies a unary callback accepting and returning single-precision floating-point numbers to each element in a single-precision floating-point strided input array and assigns results to elements in a single-precision floating-point strided output array.
```c
#include
// ...
static float identityf( const float 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_smap( env, info, identityf );
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] float (*fcn)( float )` unary callback.
```c
void stdlib_strided_napi_smap( napi_env env, napi_callback_info info, float (*fcn)( float ) );
```
#### STDLIB_STRIDED_NAPI_MODULE_SMAP( clbk )
Macro for registering a Node-API module exporting a strided array interface for applying a unary callback accepting and return single-precision floating-point numbers to each element in a single-precision floating-point strided input array and assigning results to elements in a single-precision floating-point strided output array.
```c
static float scale( const float x ) {
return x * 10.0f;
}
// ...
// Register a Node-API module:
STDLIB_STRIDED_NAPI_MODULE_SMAP( scale );
```
The macro expects the following arguments:
- **clbk**: `float (*fcn)( float )` unary callback.
When used, this macro should be used **instead of** `NAPI_MODULE`. The macro includes `NAPI_MODULE`, thus ensuring Node-API module registration.
### Notes
- The function expects that the callback `info` argument provides access to the following JavaScript arguments:
- `N`: number of indexed elements.
- `X`: input [`Float32Array`][@stdlib/array/float32].
- `strideX`: `X` stride length.
- `Y`: destination [`Float32Array`][@stdlib/array/float32].
- `strideY`: `Y` stride length.
[@stdlib/array/float32]: https://www.npmjs.com/package/@stdlib/array-float32