iterFlow

Create a fluent interface for chaining together iterator methods.

Installation

npm install @stdlib/iter-flow

Usage

var iterFlow = require( '@stdlib/iter-flow' );

iterFlow( methods )

Returns a fluent interface iterator constructor with a customized prototype based on provided methods.

var iterHead = require( '@stdlib/iter-head' );
var iterSome = require( '@stdlib/iter-some' );

// Create a mini-fluent interface having just the methods `head` and `some`:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

The methods argument should be an object which maps constructor method names to iterator functions. Each iterator function should have the following function signature:

function iterFcn( iterator[, ...args] ) {...}

where

• iterator: an iterator
• ...args: additional iterator function arguments

When a fluent interface iterator method is invoked, the method invokes the corresponding iterator function with an iterator and provided method arguments.

If an iterator function returns an iterator, the corresponding fluent interface method returns a new fluent interface instance; otherwise, the corresponding fluent interface method returns the iterator function result.

FluentIterator( iterator )

Returns a new fluent interface iterator from a source iterator.

var array2iterator = require( '@stdlib/array-to-iterator' );
var iterHead = require( '@stdlib/iter-head' );
var iterSome = require( '@stdlib/iter-some' );

// Create a mini-fluent interface having just the methods `head` and `some`:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

// Create a source iterator:
var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );

// Convert the source iterator to a fluent interface iterator:
var it = new FluentIterator( src );

// Test if at least 3 of the first 5 iterated values are truthy:
var bool = it.head( 5 ).some( 3 );
// returns true

FluentIterator.prototype.next()

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.

var array2iterator = require( '@stdlib/array-to-iterator' );
var iterHead = require( '@stdlib/iter-head' );
var iterSome = require( '@stdlib/iter-some' );

// Create a mini-fluent interface having just the methods `head` and `some`:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

// Create a source iterator:
var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );

// Create a fluent interface iterator:
var it1 = new FluentIterator( src );

// Invoke the `head` method to return an iterator limited to the first 5 source values:
var it2 = it1.head( 5 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it2.next();
    if ( v.done ) {
        break;
    }
    console.log( v.value );
}

FluentIterator.prototype.return( [value] )

Closes a fluent interface iterator and returns a single (optional) argument in an iterator protocol-compliant object.

var array2iterator = require( '@stdlib/array-to-iterator' );
var iterHead = require( '@stdlib/iter-head' );
var iterSome = require( '@stdlib/iter-some' );

// Create a mini-fluent interface having just the methods `head` and `some`:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

// Create a source iterator:
var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );

// Create a fluent interface iterator:
var it1 = new FluentIterator( src );

// Invoke the `head` method to return an iterator limited to the first 5 source values:
var it2 = it1.head( 5 );

// Get the first value:
var v = it2.next().value;
// returns 0

// Get the second value:
v = it2.next().value;
// returns 0

// Get the third value:
v = it2.next().value;
// returns 1

// Close the iterator:
var bool = it2.return().done;
// returns true

// Attempt to get the fourth value:
v = it2.next().value;
// returns undefined

Notes

• The iterator function evaluation context is always null.
• Iterator functions which return iterators are expected to return iterator protocol-compliant objects (i.e., an object having a next method which returns 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).
• If an environment supports Symbol.iterator, the returned iterator is iterable.

Examples

var array2iterator = require( '@stdlib/array-to-iterator' );
var iterHead = require( '@stdlib/iter-head' );
var iterSome = require( '@stdlib/iter-some' );
var iterFlow = require( '@stdlib/iter-flow' );

// Create a "fluent" interface:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

// Create a source iterator:
var arr = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );

// Create a new iterator:
var it = new FluentIterator( arr );

var bool = it.head( 5 ).some( 3 );
// returns true

// Create another source iterator:
arr = array2iterator( [ 0, 0, 1, 0, 1, 0, 0, 1, 0, 1 ] );

// Create a new iterator:
it = new FluentIterator( arr );

bool = it.head( 5 ).some( 3 );
// returns false

See Also

• @stdlib/iter-pipeline: create an iterator pipeline.

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.