@stdlib/iter-mapn

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iterMapN

Create an iterator which transforms iterated values from two or more iterators by applying the iterated values as arguments to a provided function.

Installation

npm install @stdlib/iter-mapn

Usage

var iterMapN = require( '@stdlib/iter-mapn' );

iterMapN( iter0, ...iterator, fcn[, thisArg] )

Returns an iterator which transforms iterated values from two or more iterators by applying the iterated values as arguments to a provided function.

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

function transform( x, y ) {
    return x + y;
}

var it1 = array2iterator( [ 1.0, 2.0 ] );
var it2 = array2iterator( [ 3.0, 4.0 ] );

var it = iterMapN( it1, it2, transform );
// returns <Object>

var v = it.next().value;
// returns 4.0

v = it.next().value;
// returns 6.0

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

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.

The invoked function is provided N+1 arguments, where N is the number of provided iterators and the last argument is the iteration index:

• ...value: iterated values
• index: iteration index (zero-based)

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

function transform( x, y, i ) {
    return x + y + i;
}

var it1 = array2iterator( [ 1.0, 2.0 ] );
var it2 = array2iterator( [ 3.0, 4.0 ] );

var it = iterMapN( it1, it2, transform );
// returns <Object>

var v = it.next().value;
// returns 4.0

v = it.next().value;
// returns 7.0

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

To set the callback execution context, provide a thisArg.

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

function transform( x, y ) {
    this.count += 1;
    return x + y;
}

var it1 = array2iterator( [ 1.0, 2.0 ] );
var it2 = array2iterator( [ 3.0, 4.0 ] );

var ctx = {
    'count': 0
};
var it = iterMapN( it1, it2, transform, ctx );
// returns <Object>

var v = it.next().value;
// returns 4.0

v = it.next().value;
// returns 6.0

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

var count = ctx.count;
// returns 2

Notes

• The length of the returned iterator is equal to the length of the shortest provided iterator. In other words, the returned iterator ends once one of the provided iterators ends.
• If an environment supports Symbol.iterator and provided iterators are iterable, the returned iterator is iterable.

Examples

var iterSineWave = require( '@stdlib/simulate-iter-sine-wave' );
var iterMapN = require( '@stdlib/iter-mapn' );

function add( x, y ) {
    return x + y;
}

// Create an iterator which generates a sine wave:
var sine1 = iterSineWave({
    'period': 50,
    'offset': 0,
    'iter': 100
});

// Create another iterator which generates a higher frequency sine wave:
var sine2 = iterSineWave({
    'period': 10,
    'offset': 0,
    'iter': 100
});

// Create an iterator which adds the two waveforms:
var it = iterMapN( sine1, sine2, add );

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

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See Also

• @stdlib/iter-map: create an iterator which invokes a function for each iterated value.

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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.