stdlib-js/iter-pipeline-thunk

Create an iterator thunk.

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iterThunk

Create an iterator "thunk".

Installation

npm install @stdlib/iter-pipeline-thunk

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 iterThunk = require( '@stdlib/iter-pipeline-thunk' );

iterThunk( iterFcn[, ...args] )

Returns an iterator "thunk".

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

var thunk = iterThunk( iterSome, 3 );

var arr = array2iterator( [ 0, 0, 1, 1, 1 ] );
var bool = thunk( arr );
// returns true

arr = array2iterator( [ 0, 0, 1, 0, 1 ] );
bool = thunk( arr );
// returns false

A provided iterator function should have the following function signature:

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

where

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

The returned function expects a single argument

• iterator: an iterator

and invokes iterFcn with the provided iterator and any previously provided args.

Accordingly, this function implements left-to-right partial application with special consideration for functions which act upon iterator sequences.

Notes

• This function is useful within the context of iterator pipelines as a means to defer execution until a pipeline is ready for data flow.
• The function evaluation context is always null.

Examples

var randu = require( '@stdlib/random-iter-randu' );
var iterHead = require( '@stdlib/iter-head' );
var iterMap = require( '@stdlib/iter-map' );
var iterSome = require( '@stdlib/iter-some' );
var iterPipeline = require( '@stdlib/iter-pipeline' );
var iterThunk = require( '@stdlib/iter-pipeline-thunk' );

function threshold( r ) {
    return ( r > 0.95 );
}

// Create a pipeline which tests whether at least 5% of values exceed a threshold:
var p = iterPipeline(
    // Apply a threshold to iterated values:
    iterThunk( iterMap, threshold ),

    // Limit the sequence to 100 values:
    iterThunk( iterHead, 100 ),

    // Test whether at least 5 values exceed the threshold:
    iterThunk( iterSome, 5 )
);

// Define the number of random number sequences to analyze:
var N = 100;

// Initialize a counter for sequences satisfying the 5% threshold:
var count = 0;

// Perform analysis...
var bool;
var i;
for ( i = 0; i < N; i++ ) {
    bool = p( randu() );
    if ( bool ) {
        count += 1;
    }
    console.log( bool );
}
console.log( '%d of %d', count, N );

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See Also

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

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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.