@stdlib/iter-to-array-view

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

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README

iterator2arrayview

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

Installation

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

Usage

var iterator2arrayview = require( '@stdlib/iter-to-array-view' );

iterator2arrayview( iterator, dest[, begin[, end]][, mapFcn[, thisArg]] )

Fills an array-like object view 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 = iterator2arrayview( iter, new Uint8Array( 10 ) );
// returns <Uint8Array>[ 1, 2, 3, 4, 0, 0, 0, 0, 0, 0 ]

By default, the function begins filling from the first element of a provided array-like object. To specify an alternative starting index, 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 ] );

var arr = iterator2arrayview( iter, new Uint8Array( 10 ), 3 );
// returns <Uint8Array>[ 0, 0, 0, 1, 2, 3, 4, 0, 0, 0 ]

If begin is less than 0, the starting 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 ] );

var arr = iterator2arrayview( iter, new Uint8Array( 10 ), -7 );
// returns <Uint8Array>[ 0, 0, 0, 1, 2, 3, 4, 0, 0, 0 ]

By default, the function assumes that a view extends through the last element of a provided array-like object. To specify an alternative last view element, 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 = iterator2arrayview( iter, new Uint8Array( 10 ), 0, 4 );
// returns <Uint8Array>[ 1, 2, 3, 4, 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 = iterator2arrayview( iter, new Uint8Array( 10 ), 0, -6 );
// returns <Uint8Array>[ 1, 2, 3, 4, 0, 0, 0, 0, 0, 0 ]

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 = iterator2arrayview( iter, new Float64Array( 4 ), fcn );
// returns <Float64Array>[ 10.0, 20.0, 30.0, 40.0 ]

The invoked function is provided three arguments:

  • value: iterated value
  • index: destination index
  • n: iteration count (zero-based)
var Uint8Array = require( '@stdlib/array-uint8' );
var array2iterator = require( '@stdlib/array-to-iterator' );

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

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

var arr = iterator2arrayview( iter, new Uint8Array( 4 ), fcn );
// returns <Uint8Array>[ 1, 4, 9, 16 ]

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 = iterator2arrayview( 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.

Examples

var Float64Array = require( '@stdlib/array-float64' );
var randu = require( '@stdlib/random-iter-randu' );
var iterator2arrayview = require( '@stdlib/iter-to-array-view' );

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

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

// Fill an array view with scaled iterator values:
var arr = iterator2arrayview( 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.

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License

See LICENSE.

Copyright

Copyright © 2016-2021. The Stdlib Authors.