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Add utility to create an iterator pipeline
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‎lib/node_modules/@stdlib/iter/pipeline/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2019 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# iterPipeline
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> Create an [iterator][mdn-iterator-protocol] pipeline.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var iterPipeline = require( '@stdlib/iter/pipeline' );
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```
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#### iterPipeline( iterFcn0\[, ...iterFcn] )
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Returns an [iterator][mdn-iterator-protocol] pipeline.
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```javascript
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var array2iterator = require( '@stdlib/array/to-iterator' );
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var iterThunk = require( '@stdlib/iter/pipeline-thunk' );
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var iterHead = require( '@stdlib/iter/head' );
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var iterSome = require( '@stdlib/iter/some' );
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// Convert iterator functions to unary functions which accept an iterator:
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var it1 = iterThunk( iterHead, 5 );
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var it2 = iterThunk( iterSome, 3 );
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// Create an iterator pipeline:
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var p = iterPipeline( it1, it2 );
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// Create a source iterator:
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var arr = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 0, 1, 1 ] );
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// Provide the source iterator to our iterator pipeline:
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var bool = p( arr );
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// returns true
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// Create a new source iterator:
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arr = array2iterator( [ 0, 0, 1, 0, 1, 0, 0, 0, 1, 1 ] );
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// Run the pipeline for the new source iterator:
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bool = p( arr );
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// returns false
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```
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The function accepts [iterator][mdn-iterator-protocol] functions provided as separate arguments **or** as a single argument consisting of an array of [iterator][mdn-iterator-protocol] functions.
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```javascript
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var array2iterator = require( '@stdlib/array/to-iterator' );
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var iterThunk = require( '@stdlib/iter/pipeline-thunk' );
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var iterHead = require( '@stdlib/iter/head' );
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var iterSome = require( '@stdlib/iter/some' );
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var it1 = iterThunk( iterHead, 5 );
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var it2 = iterThunk( iterSome, 3 );
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var p = iterPipeline( [ it1, it2 ] );
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var arr = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 0, 1, 1 ] );
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var bool = p( arr );
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// returns true
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arr = array2iterator( [ 0, 0, 1, 0, 1, 0, 0, 0, 1, 1 ] );
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bool = p( arr );
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// returns false
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```
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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## Notes
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- Within the context of an [iterator][mdn-iterator-protocol] pipeline (as defined by this function), an [iterator][mdn-iterator-protocol] function is defined as a **unary** function which accepts an [iterator][mdn-iterator-protocol] as its **only** argument.
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- Each [iterator][mdn-iterator-protocol] function, except the last [iterator][mdn-iterator-protocol] function, within an [iterator][mdn-iterator-protocol] pipeline must return an [iterator][mdn-iterator-protocol].
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- Starting from the left, each returned [iterator][mdn-iterator-protocol] is passed to the next [iterator][mdn-iterator-protocol] function.
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- The result of the last [iterator][mdn-iterator-protocol] function is the result of the pipeline.
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint-disable function-paren-newline -->
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<!-- eslint no-undef: "error" -->
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```javascript
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var randu = require( '@stdlib/random/iter/randu' );
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var iterHead = require( '@stdlib/iter/head' );
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var iterMap = require( '@stdlib/iter/map' );
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var iterSome = require( '@stdlib/iter/some' );
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var iterThunk = require( '@stdlib/iter/pipeline-thunk' );
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var iterPipeline = require( '@stdlib/iter/pipeline' );
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function threshold( r ) {
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return ( r > 0.95 );
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}
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// Create a pipeline which tests whether at least 5% of values exceed a threshold:
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var p = iterPipeline(
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// Apply a threshold to iterated values:
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iterThunk( iterMap, threshold ),
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// Limit the sequence to 100 values:
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iterThunk( iterHead, 100 ),
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// Test whether at least 5 values exceed the threshold:
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iterThunk( iterSome, 5 )
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);
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// Define the number of random number sequences to analyze:
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var N = 100;
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// Initialize a counter for sequences satisfying the 5% threshold:
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var count = 0;
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// Perform analysis...
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var bool;
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var i;
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for ( i = 0; i < N; i++ ) {
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bool = p( randu() );
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if ( bool ) {
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count += 1;
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}
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console.log( bool );
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}
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console.log( '%d of %d', count, N );
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/iter/pipeline/benchmark/benchmark.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2019 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var isFunction = require( '@stdlib/assert/is-function' );
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var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
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var randu = require( '@stdlib/random/iter/randu' );
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var iterHead = require( '@stdlib/iter/head' );
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var iterSomeBy = require( '@stdlib/iter/some-by' );
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var iterThunk = require( '@stdlib/iter/pipeline-thunk' );
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var pkg = require( './../package.json' ).name;
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var iterPipeline = require( './../lib' );
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// MAIN //
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bench( pkg+'::arguments', function benchmark( b ) {
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var fcn;
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var it1;
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var it2;
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var i;
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it1 = iterThunk( iterHead, 10 );
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it2 = iterThunk( iterSomeBy, 5, threshold );
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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fcn = iterPipeline( it1, it2 );
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if ( !isFunction( fcn ) ) {
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b.fail( 'should return a function' );
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}
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}
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b.toc();
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if ( !isFunction( fcn ) ) {
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b.fail( 'should return a function' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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function threshold( r ) {
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return ( r > 0.95 );
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}
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});
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bench( pkg+'::array', function benchmark( b ) {
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var args;
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var fcn;
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var it1;
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var it2;
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var i;
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it1 = iterThunk( iterHead, 10 );
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it2 = iterThunk( iterSomeBy, 5, threshold );
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args = [ it1, it2 ];
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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fcn = iterPipeline( args );
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if ( !isFunction( fcn ) ) {
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b.fail( 'should return a function' );
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}
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}
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b.toc();
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if ( !isFunction( fcn ) ) {
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b.fail( 'should return a function' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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function threshold( r ) {
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return ( r > 0.95 );
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}
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});
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bench( pkg+'::pipeline_throughput', function benchmark( b ) {
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var bool;
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var fcn;
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var it0;
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var it1;
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var it2;
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var i;
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it0 = randu(); // infinite iterator which can be reused for each run
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it1 = iterThunk( iterHead, 10 );
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it2 = iterThunk( iterSomeBy, 5, threshold );
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fcn = iterPipeline( it1, it2 );
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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bool = fcn( it0 );
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if ( !isBoolean( bool ) ) {
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b.fail( 'should return a boolean' );
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}
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}
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b.toc();
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if ( !isBoolean( bool ) ) {
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b.fail( 'should return a boolean' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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function threshold( r ) {
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return ( r > 0.95 );
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}
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});

‎lib/node_modules/@stdlib/iter/pipeline/docs/repl.txt

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{{alias}}( iterFcn[, ...iterFcn] )
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Returns an iterator pipeline.
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Parameters
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----------
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iterFcn: Function|Array
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Iterator function or an array of iterator functions.
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...iterFcn: Function (optional)
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Iterator functions.
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Returns
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-------
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fcn( src ): Function
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Iterator pipeline which accepts a single argument, a source iterator.
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Examples
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--------
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> var it1 = {{alias:@stdlib/iter/pipeline-thunk}}( {{alias:@stdlib/iter/head}}, 100 );
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> function f( r ) { return ( r > 0.95 ); };
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> var it2 = {{alias:@stdlib/iter/pipeline-thunk}}( {{alias:@stdlib/iter/some-by}}, 5, f );
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> var p = {{alias}}( it1, it2 );
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> var bool = p( {{alias:@stdlib/random/iter/randu}}() )
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<boolean>
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See Also
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--------
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