iterMap

Create an iterator which invokes a unary function accepting a single numeric argument for each iterated value.

Installation

npm install @stdlib/math-iter-tools-map

Usage

var iterMap = require( '@stdlib/math-iter-tools-map' );

iterMap( iterator, fcn[, options] )

Returns an iterator which invokes a unary function accepting a single numeric argument for each iterated value.

var array2iterator = require( '@stdlib/array-to-iterator' );
var sin = require( '@stdlib/math-base-special-sin' );

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

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

// ...

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 one argument:

• value: iterated value

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

function fcn( v ) {
    return v + 10;
}

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

var r = it.next().value;
// returns 11

r = it.next().value;
// returns 12

r = it.next().value;
// returns 13

// ...

The function supports the following options:

• invalid: return value when an input iterator yields a non-numeric value. Default: NaN.

By default, the function returns an iterator which returns NaN when an input iterator yields a non-numeric value. To specify a different return value, set the invalid option.

var array2iterator = require( '@stdlib/array-to-iterator' );
var sin = require( '@stdlib/math-base-special-sin' );

var opts = {
    'invalid': null
};
var it = iterMap( array2iterator( [ '1', '2', '3' ] ), sin, opts );
// returns <Object>

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

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

// ...

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 sin = require( '@stdlib/math-base-special-sin' );
var iterMap = require( '@stdlib/math-iter-tools-map' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which consumes the pseudorandom number iterator:
var it = iterMap( rand, sin );

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

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

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.