@stdlib/iter-to-array-view-right NPM

iterator2arrayviewRight

Fill an array-like object view from right to left with values returned from an iterator.

Installation

npm install @stdlib/iter-to-array-view-right

Usage

var iterator2arrayviewRight = require( '@stdlib/iter-to-array-view-right' );

iterator2arrayviewRight( iterator, dest[, begin[, end]][, mapFcn[, thisArg]] )

Fills an array-like object view from right to left with values returned from an iterator.

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

var iter = array2iterator( [ 1, 2, 3, 4 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 10 ) );
// returns <Uint8Array>[ 0, 0, 0, 0, 0, 0, 4, 3, 2, 1 ]

The begin and end arguments define the starting (inclusive) and ending (non-inclusive) indices of the array view. By default, the function begins filling from the last element of a provided array-like object (i.e., from the "end"). To specify an alternative view end, provide an end argument (zero-based and non-inclusive).

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 10 ), 0, 4 );
// returns <Uint8Array>[ 4, 3, 2, 1, 0, 0, 0, 0, 0, 0 ]

If end is less than 0, the last view element is resolved relative to the last element of the provided array-like object. For example, the following achieves the same behavior as the previous example

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 10 ), 0, -6 );
// returns <Uint8Array>[ 4, 3, 2, 1, 0, 0, 0, 0, 0, 0 ]

By default, the function fills through the first element of the provided array-like object. To specify an alternative view beginning, provide a begin argument (zero-based and inclusive).

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 10 ), 3 );
// returns <Uint8Array>[ 0, 0, 0, 7, 6, 5, 4, 3, 2, 1 ]

If begin is less than 0, the first view element index is resolved relative to the last element of the provided array-like object. For example, the following achieves the same behavior as the previous example

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

var iter = array2iterator( [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 10 ), -7 );
// returns <Uint8Array>[ 0, 0, 0, 7, 6, 5, 4, 3, 2, 1 ]

To invoke a function for each iterated value, provide a callback function.

var Float64Array = require( '@stdlib/array-float64' );
var array2iterator = require( '@stdlib/array-to-iterator' );

function fcn( v ) {
    return v * 10.0;
}

var iter = array2iterator( [ 1, 2, 3, 4 ] );

var arr = iterator2arrayviewRight( iter, new Float64Array( 4 ), fcn );
// returns <Float64Array>[ 40.0, 30.0, 20.0, 10.0 ]

The invoked function is provided three arguments:

value: iterated value.
index: destination index (zero-based).
n: iteration index (zero-based).

var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

function fcn( v, i, n ) {
    return v * (n+1);
}

var iter = array2iterator( [ 1, 2, 3, 4 ] );

var arr = iterator2arrayviewRight( iter, new Uint8Array( 4 ), fcn );
// returns <Uint8Array>[ 16, 9, 4, 1 ]

To set the callback function execution context, provide a thisArg.

var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-iter-randu' );

function fcn( v ) {
    this.count += 1;
    return v * 10.0;
}

var ctx = {
    'count': 0
};

var arr = iterator2arrayviewRight( randu(), new Float64Array( 10 ), fcn, ctx );
// returns <Float64Array>

var count = ctx.count;
// returns 10

Notes

Iteration stops when an output array view is full or an iterator finishes; whichever comes first.
The function supports output array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array-complex64).

Examples

var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-iter-randu' );
var iterator2arrayviewRight = require( '@stdlib/iter-to-array-view-right' );

function scale( v, i, n ) {
    return v * (n+1) * 10.0;
}

// Create an iterator for generating uniformly distributed pseudorandom numbers:
var it = randu();

// Fill an array view with scaled iterator values:
var arr = iterator2arrayviewRight( it, new Float64Array( 100 ), 40, 60, scale );

var i;
for ( i = 0; i < arr.length; i++ ) {
    console.log( arr[ i ] );
}

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.