README.md

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iterSlice

Create an iterator which returns a subsequence of iterated values from a provided iterator.

Installation

npm install @stdlib/iter-slice

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var iterSlice = require( '@stdlib/iter-slice' );

iterSlice( iterator[, begin[, end]] )

Returns an iterator which returns a subsequence of iterated values from a provided iterator.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ) );
// returns <Object>

var v = it.next().value;
// returns 1

v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

// ...

The returned iterator protocol-compliant object has the following properties:

• next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
• return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

By default, the returned iterator returns a provided iterator's first iterated value through an iterator's last iterated value. To specify an alternative start iteration index (zero-based and inclusive), provide a begin argument.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 2 );
// returns <Object>

var v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

var bool = it.next().done;
// returns true

By default, the returned iterator continues iterating until it consumes all of a provided iterator's iterated values. To specify an end iteration index (zero-based and non-inclusive), provide an end argument.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 1, 3 );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

var bool = it.next().done;
// returns true

If begin is greater than or equal to end, the returned iterator does not return any iterated values.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 3, 1 );
// returns <Object>

var bool = it.next().done;
// returns true

Notes

• If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.

Examples

var randu = require( '@stdlib/random-iter-randu' );
var iterSlice = require( '@stdlib/iter-slice' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234
});

// Create an iterator which returns a subsequence of 10 generated numbers:
var it = iterSlice( rand, 10, 20 );

// Perform manual iteration...
var r;
while ( true ) {
    r = it.next();
    if ( r.done ) {
        break;
    }
    console.log( r.value );
}

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See Also

• @stdlib/iter-first: return the first iterated value.
• @stdlib/iter-head: create an iterator which returns the first n values of a provided iterator.

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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.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.