iterReplicateBy

Create an iterator which replicates each iterated value according to a provided function.

Usage

var iterReplicateBy = require( '@stdlib/iter/replicate-by' );

iterReplicateBy( iterator, fcn[, thisArg] )

Returns an iterator which replicates each iterated value according to a provided function.

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

function fcn( v, i ) {
    return i + 1;
}

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

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

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

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

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

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

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

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

// ...

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 callback function is provided three arguments:

  • value: iterated value
  • index: source iteration index (zero-based)
  • n: iteration index (zero-based)

To set the callback execution context, provide a thisArg.

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

function fcn( v, i ) {
    this.count += 1;
    return i + 1;
}

var ctx = {
    'count': 0
};

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

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

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

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

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

var count = ctx.count;
// returns 3

Notes

  • A callback function is invoked once per iterated value of the provided iterator.
  • A callback function must return an integer value. If the return value is less than or equal to 0, the returned iterator skips an iterated value and invokes the callback for the next iterated value of the provided iterator.
  • 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 discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var iterReplicateBy = require( '@stdlib/iter/replicate-by' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which replicates each generated number a random number of times:
var it = iterReplicateBy( rand, discreteUniform.factory( 1, 10 ) );

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