# fillSlice
> Fill an input [`ndarray`][@stdlib/ndarray/ctor] view with a specified value.
## Usage
```javascript
var fillSlice = require( '@stdlib/ndarray/fill-slice' );
```
#### fillSlice( x, value, ...s\[, options] )
Fills an input [`ndarray`][@stdlib/ndarray/ctor] view with a specified value.
```javascript
var zeros = require( '@stdlib/ndarray/zeros' );
var MultiSlice = require( '@stdlib/slice/multi' );
var Slice = require( '@stdlib/slice/ctor' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var x = zeros( [ 3, 4 ], {
'dtype': 'float64'
});
// Define the fill region:
var s0 = new Slice( 1, 3 );
var s1 = new Slice( 2, 4 );
var s = new MultiSlice( s0, s1 );
// Fill the region with a scalar value:
var y = fillSlice( x, 5.0, s );
// returns
var bool = ( y === x );
// returns true
var arr = ndarray2array( x );
// returns [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 5.0, 5.0 ], [ 0.0, 0.0, 5.0, 5.0 ] ]
```
The function accepts the following arguments:
- **x**: input [`ndarray`][@stdlib/ndarray/ctor].
- **value**: fill value.
- **s**: a [`MultiSlice`][@stdlib/slice/multi] instance, an array of slice arguments, or slice arguments as separate arguments.
- **options**: function options.
The function supports three (mutually exclusive) means for providing slice arguments:
1. providing a single [`MultiSlice`][@stdlib/slice/multi] instance.
2. providing a single array of slice arguments.
3. providing slice arguments as separate arguments.
The following example demonstrates each invocation style achieving equivalent results.
```javascript
var zeros = require( '@stdlib/ndarray/zeros' );
var MultiSlice = require( '@stdlib/slice/multi' );
var Slice = require( '@stdlib/slice/ctor' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var opts = {
'dtype': 'float64'
};
// 1. Using a MultiSlice:
var x = zeros( [ 3, 4 ], opts );
var s0 = new Slice( 1, 3 );
var s1 = new Slice( 2, 4 );
var s = new MultiSlice( s0, s1 );
var out = fillSlice( x, 5.0, s );
// returns
var arr = ndarray2array( out );
// returns [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 5.0, 5.0 ], [ 0.0, 0.0, 5.0, 5.0 ] ]
// 2. Using an array of slice arguments:
x = zeros( [ 3, 4 ], opts );
out = fillSlice( x, 6.0, [ s0, s1 ] );
// returns
arr = ndarray2array( out );
// returns [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 6.0, 6.0 ], [ 0.0, 0.0, 6.0, 6.0 ] ]
// 3. Providing separate arguments:
x = zeros( [ 3, 4 ], opts );
out = fillSlice( x, 7.0, s0, s1 );
// returns
arr = ndarray2array( out );
// returns [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 7.0, 7.0 ], [ 0.0, 0.0, 7.0, 7.0 ] ]
```
The function supports the following options:
- **strict**: boolean indicating whether to enforce strict bounds checking.
By default, the function throws an error when provided a slice which exceeds array bounds. To ignore slice indices exceeding array bounds, set the `strict` option to `false`.
```javascript
var zeros = require( '@stdlib/ndarray/zeros' );
var MultiSlice = require( '@stdlib/slice/multi' );
var Slice = require( '@stdlib/slice/ctor' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var x = zeros( [ 3, 4 ], {
'dtype': 'float64'
});
// Define the fill region:
var s0 = new Slice( 1, null, 1 );
var s1 = new Slice( 10, 20, 1 );
var s = new MultiSlice( s0, s1 );
// Fill the region with a scalar value:
var y = fillSlice( x, 5.0, s, {
'strict': false
});
// returns
var arr = ndarray2array( x );
// returns [ [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 0.0, 0.0 ] ]
```
## Notes
- An input [`ndarray`][@stdlib/ndarray/ctor] **must** be writable. If provided a **read-only** [`ndarray`][@stdlib/ndarray/ctor], the function throws an error.
- A **slice argument** must be either a [`Slice`][@stdlib/slice/ctor], an integer, `null`, or `undefined`.
- If a fill value is a number and `x` has a complex [data type][@stdlib/ndarray/dtypes], the function fills an input [`ndarray`][@stdlib/ndarray/ctor] with a complex number whose real component equals the provided fill `value` and whose imaginary component is zero.
- A fill value must be able to safely cast to the input [`ndarray`][@stdlib/ndarray/ctor] [data type][@stdlib/ndarray/dtypes]. Fill values having floating-point data types (both real and complex) are allowed to downcast to a lower precision data type of the same kind (e.g., a scalar double-precision floating-point number can be used to fill a `'float32'` input [`ndarray`][@stdlib/ndarray/ctor]).
- The function **mutates** the input [`ndarray`][@stdlib/ndarray/ctor].
## Examples
```javascript
var zeros = require( '@stdlib/ndarray/zeros' );
var MultiSlice = require( '@stdlib/slice/multi' );
var Slice = require( '@stdlib/slice/ctor' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var fillSlice = require( '@stdlib/ndarray/fill-slice' );
// Create a zero-filled ndarray:
var x = zeros( [ 2, 3, 4 ], {
'dtype': 'generic'
});
console.log( ndarray2array( x ) );
// Specify the fill region:
var s0 = new Slice( 1, 2 );
var s1 = new Slice( null, null );
var s2 = new Slice( 2, 4 );
var s = new MultiSlice( s0, s1, s2 );
// Fill a slice with a scalar value:
fillSlice( x, 10.0, s );
console.log( ndarray2array( x ) );
```
[@stdlib/slice/multi]: https://www.npmjs.com/package/@stdlib/slice-multi
[@stdlib/slice/ctor]: https://www.npmjs.com/package/@stdlib/slice-ctor
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray/tree/main/ctor
[@stdlib/ndarray/dtypes]: https://github.com/stdlib-js/ndarray/tree/main/dtypes