# sfill
> Fill a single-precision floating-point strided array with a specified scalar constant.
## Usage
```javascript
var sfill = require( '@stdlib/blas/ext/base/sfill' );
```
#### sfill( N, alpha, x, strideX )
Fills a single-precision floating-point strided array `x` with a specified scalar constant `alpha`.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sfill( x.length, 5.0, x, 1 );
// x => [ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]
```
The function has the following parameters:
- **N**: number of indexed elements.
- **alpha**: scalar constant.
- **x**: input [`Float32Array`][@stdlib/array/float32].
- **strideX**: index increment.
The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to fill every other element
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sfill( 4, 5.0, x, 2 );
// x => [ 5.0, 1.0, 5.0, -5.0, 5.0, 0.0, 5.0, -3.0 ]
```
Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
// Initial array...
var x0 = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
// Create an offset view...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
// Fill every other element...
sfill( 3, 5.0, x1, 2 );
// x0 => [ 1.0, 5.0, 3.0, 5.0, 5.0, 5.0 ]
```
#### sfill.ndarray( N, alpha, x, strideX, offsetX )
Fills a single-precision floating-point strided array `x` with a specified scalar constant `alpha` using alternative indexing semantics.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sfill.ndarray( x.length, 5.0, x, 1, 0 );
// x => [ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]
```
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 Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
sfill.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => [ 1.0, -2.0, 3.0, 5.0, 5.0, 5.0 ]
```
## Notes
- If `N <= 0`, both functions return the strided array unchanged.
## Examples
```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var sfill = require( '@stdlib/blas/ext/base/sfill' );
var x = discreteUniform( 10, -100, 100, {
'dtype': 'float32'
});
console.log( x );
sfill( x.length, 5.0, x, 1 );
console.log( x );
```
* * *
## C APIs
### Usage
```c
#include "stdlib/blas/ext/base/sfill.h"
```
#### stdlib_strided_sfill( N, alpha, \*X, strideX )
Fills a single-precision floating-point strided array `X` with a specified scalar constant `alpha`.
```c
float x[] = { 1.0f, 2.0f, 3.0f, 4.0f };
stdlib_strided_sfill( 4, 5.0f, x, 1 );
```
The function accepts the following arguments:
- **N**: `[in] CBLAS_INT` number of indexed elements.
- **alpha**: `[in] float` scalar constant.
- **X**: `[out] float*` input array.
- **strideX**: `[in] CBLAS_INT` index increment for `X`.
```c
void stdlib_strided_sfill( const CBLAS_INT N, const float alpha, float *X, const CBLAS_INT strideX );
```
#### stdlib_strided_sfill_ndarray( N, alpha, \*X, strideX, offsetX )
Fills a single-precision floating-point strided array `X` with a specified scalar constant `alpha` using alternative indexing semantics.
```c
float x[] = { 1.0f, 2.0f, 3.0f, 4.0f };
stdlib_strided_sfill_ndarray( 4, 5.0f, x, 1, 0 );
```
The function accepts the following arguments:
- **N**: `[in] CBLAS_INT` number of indexed elements.
- **alpha**: `[in] float` scalar constant.
- **X**: `[out] float*` input array.
- **strideX**: `[in] CBLAS_INT` index increment for `X`.
- **offsetX**: `[in] CBLAS_INT` starting index for `X`.
```c
void stdlib_strided_sfill_ndarray( const CBLAS_INT N, const float alpha, float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
```
### Examples
```c
#include "stdlib/blas/ext/base/sfill.h"
#include
int main( void ) {
// Create a strided array:
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 = 8;
// Specify a stride:
const int strideX = 1;
// Fill the array:
stdlib_strided_sfill( N, 5.0f, x, strideX );
// Print the result:
for ( int i = 0; i < 8; i++ ) {
printf( "x[ %i ] = %f\n", i, x[ i ] );
}
}
```
[@stdlib/array/float32]: https://www.npmjs.com/package/@stdlib/array-float32
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@stdlib/blas/ext/base/dfill]: https://github.com/stdlib-js/blas/tree/main/ext/base/dfill
[@stdlib/blas/ext/base/gfill]: https://github.com/stdlib-js/blas/tree/main/ext/base/gfill