time-to-botec/js/node_modules/@stdlib/strided/base/nullary/README.md

Nullary

Apply a nullary callback and assign results to elements in a strided output array.

Usage

var nullary = require( '@stdlib/strided/base/nullary' );

nullary( arrays, shape, strides, fcn )

Applies a nullary callback and assigns results to elements in a strided output array.

var Float64Array = require( '@stdlib/array/float64' );

function fill() {
    return 3.0;
}

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

nullary( [ x ], [ x.length ], [ 1 ], fill );
// x => <Float64Array>[ 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0 ]

The function accepts the following arguments:

• arrays: array-like object containing one strided output array.
• shape: array-like object containing a single element, the number of indexed elements.
• strides: array-like object containing the stride length for the strided output array.
• fcn: nullary function to apply.

The shape and strides parameters determine which elements in the strided output array are accessed at runtime. For example, to index the first N elements of the strided output array in reverse order,

var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

function fill() {
    return 3.0;
}

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var N = floor( x.length / 2 );

nullary( [ x ], [ N ], [ -1 ], fill );
// x => <Float64Array>[ 3.0, 3.0, 3.0, -4.0, -5.0, -6.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

function fill() {
    return 3.0;
}

// Initial arrays...
var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var N = floor( x0.length / 2 );

nullary( [ x1 ], [ N ], [ 1 ], fill );
// x0 => <Float64Array>[ -1.0, 3.0, -3.0, 3.0, -5.0, 3.0 ]

nullary.ndarray( arrays, shape, strides, offsets, fcn )

Applies a nullary callback and assigns results to elements in a strided output array using alternative indexing semantics.

var Float64Array = require( '@stdlib/array/float64' );

function fill() {
    return 3.0;
}

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );

nullary.ndarray( [ x ], [ x.length ], [ 1 ], [ 0 ], fill );
// x => <Float64Array>[ 3.0, 3.0, 3.0, 3.0, 3.0 ]

The function accepts the following additional arguments:

• offsets: array-like object containing the starting index (i.e., index offset) for the strided output array.

While typed array views mandate a view offset based on the underlying buffer, the offsets parameter supports indexing semantics based on starting indices. For example, to index the last N elements in the strided output array,

var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

function fill() {
    return 3.0;
}

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var N = floor( x.length / 2 );

nullary.ndarray( [ x ], [ N ], [ -1 ], [ x.length-1 ], fill );
// x => <Float64Array>[ -1.0, -2.0, -3.0, 3.0, 3.0, 3.0 ]

Examples

var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarray = require( '@stdlib/array/filled' );
var nullary = require( '@stdlib/strided/base/nullary' );

var N = 10;

var x = filledarray( 0.0, N, 'generic' );
console.log( x );

var shape = [ N ];
var strides = [ 1 ];
var offsets = [ 0 ];

nullary.ndarray( [ x ], shape, strides, offsets, discreteUniform( -100, 100 ) );
console.log( x );