iterDedupe

Create an iterator which removes consecutive duplicated values.

Installation

npm install @stdlib/iter-dedupe

Usage

var iterDedupe = require( '@stdlib/iter-dedupe' );

iterDedupe( iterator[, limit] )

Returns an iterator which removes consecutive duplicated values.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 3, 3, 3, 4, 4 ] ) );
// 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 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 returned iterator removes consecutive duplicated values and does not return globally unique values.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 1, 1, 2 ] ) );
// 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 second argument.

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

var it = iterDedupe( array2iterator( [ 1, 1, 2, 3, 3, 3, 3, 4, 4, 4 ] ), 2 );
// 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

• NaN values are considered distinct.

  var array2iterator = require( '@stdlib/array-to-iterator' );
  
  var it = iterDedupe( array2iterator( [ NaN, NaN, NaN, NaN ] ) );
  // returns <Object>
  
  var v = it.next().value;
  // returns NaN
  
  v = it.next().value;
  // returns NaN
  
  v = it.next().value;
  // returns NaN
  
  v = it.next().value;
  // returns NaN
  
  var bool = it.next().done;
  // returns true

• Uniqueness is determined according to strict equality. Accordingly, objects are not checked for deep equality.

  var array2iterator = require( '@stdlib/array-to-iterator' );
  
  var it = iterDedupe( array2iterator( [ {}, {}, {}, {} ] ) );
  // returns <Object>
  
  var v = it.next().value;
  // returns {}
  
  v = it.next().value;
  // returns {}
  
  v = it.next().value;
  // returns {}
  
  v = it.next().value;
  // returns {}
  
  var bool = it.next().done;
  // returns true

• 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' );

// Create a seeded iterator for generating pseudorandom integers on the interval [1,3]:
var rand = randi( 1, 3, {
    'seed': 1234,
    'iter': 100
});

// Create an iterator which limits "runs" to at most 3 values:
var it = iterDedupe( rand, 3 );

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

See Also

• @stdlib/iter-dedupe-by: create an iterator which removes consecutive values that resolve to the same value according to a provided function.
• @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.