iterSlice

Create an iterator which returns a subsequence of iterated values from a provided iterator.

Usage

var iterSlice = require( '@stdlib/iter/slice' );

iterSlice( iterator[, begin[, end]] )

Returns an iterator which returns a subsequence of iterated values from a provided iterator.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ) );
// returns <Object>

var v = it.next().value;
// returns 1

v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

// ...

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.

By default, the returned iterator returns a provided iterator's first iterated value through an iterator's last iterated value. To specify an alternative start iteration index (zero-based and inclusive), provide a begin argument.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 2 );
// returns <Object>

var v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

var bool = it.next().done;
// returns true

By default, the returned iterator continues iterating until it consumes all of a provided iterator's iterated values. To specify an end iteration index (zero-based and non-inclusive), provide an end argument.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 1, 3 );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

var bool = it.next().done;
// returns true

If begin is greater than or equal to end, the returned iterator does not return any iterated values.

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

var it = iterSlice( array2iterator( [ 1, 2, 3, 4 ] ), 3, 1 );
// returns <Object>

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 randu = require( '@stdlib/random/iter/randu' );
var iterSlice = require( '@stdlib/iter/slice' );

var rand;
var it;
var r;

// Create a seeded iterator for generating pseudorandom numbers:
rand = randu({
    'seed': 1234
});

// Create an iterator which returns a subsequence of 10 generated numbers:
it = iterSlice( rand, 10, 20 );

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