@stdlib/iter-dedupe-by
v0.2.2
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Create an iterator which removes consecutive values that resolve to the same value according to a provided function.
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iterDedupeBy
Create an iterator which removes consecutive values that resolve to the same value according to a provided function.
Installation
npm install @stdlib/iter-dedupe-by
Usage
var iterDedupeBy = require( '@stdlib/iter-dedupe-by' );
iterDedupeBy( iterator, [limit,] fcn )
Returns an iterator which removes consecutive values that resolve to the same value according to a provided function.
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
return v;
}
var arr = array2iterator( [ 1, 1, 2, 3, 3, 3, 4, 4 ] );
var it = iterDedupeBy( arr, fcn );
// returns <Object>
var v = it.next().value;
// returns 1
v = it.next().value;
// returns 2
v = it.next().value;
// returns 3
v = it.next().value;
// returns 4
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 adone
property having aboolean
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 callback function is provided five arguments:
- curr: current source iterated value.
- sprev: previous source iterated value.
- dprev: previous downstream iterated value.
- index: source iteration index (zero-based).
- acc: previous resolved value.
The returned iterator removes consecutive values which resolve to the same value and does not return globally "unique" values.
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
return v;
}
var arr = array2iterator( [ 1, 1, 2, 1, 1, 2 ] );
var it = iterDedupeBy( arr, fcn );
// returns <Object>
var v = it.next().value;
// returns 1
v = it.next().value;
// returns 2
v = it.next().value;
// returns 1
v = it.next().value;
// returns 2
var bool = it.next().done;
// returns true
To specify the number of allowed consecutive duplicated values, provide a limit
argument.
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
return v;
}
var arr = array2iterator( [ 1, 1, 2, 3, 3, 3, 3, 4, 4, 4 ] );
var it = iterDedupeBy( arr, 2, fcn );
// returns <Object>
var v = it.next().value;
// returns 1
v = it.next().value;
// returns 1
v = it.next().value;
// returns 2
v = it.next().value;
// returns 3
v = it.next().value;
// returns 3
v = it.next().value;
// returns 4
v = it.next().value;
// returns 4
var bool = it.next().done;
// returns true
Notes
- If an environment supports
Symbol.iterator
and a provided iterator is iterable, the returned iterator is iterable.
Examples
var randi = require( '@stdlib/random-iter-discrete-uniform' );
var iterDedupe = require( '@stdlib/iter-dedupe' );
var iterDedupeBy = require( '@stdlib/iter-dedupe-by' );
function fcn( curr, sprev, dprev, i, acc ) {
if ( curr < dprev ) {
return 1;
}
if ( curr === dprev ) {
return acc; // ensures that duplicate values are removed
}
// curr > dprev
return -1;
}
// Create a seeded iterator for generating pseudorandom integers:
var rand = randi( 1, 10, {
'seed': 1234,
'iter': 100
});
// Create an iterator which removes consecutive duplicated values:
var deduped = iterDedupe( rand );
// Create an iterator which forces consecutive values to follow an alternating less than, greater than pattern:
var it = iterDedupeBy( deduped, fcn );
// Perform manual iteration...
var v;
while ( true ) {
v = it.next();
if ( v.done ) {
break;
}
console.log( v.value );
}
See Also
@stdlib/iter-dedupe
: create an iterator which removes consecutive duplicated values.@stdlib/iter-unique
: create an iterator which returns unique values.
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.