iterMap

Create an iterator which invokes a unary function accepting a single numeric argument for each iterated value.

Usage

var iterMap = require( '@stdlib/math/iter/tools/map' );

iterMap( iterator, fcn[, options] )

Returns an iterator which invokes a unary function accepting a single numeric argument for each iterated value.

var array2iterator = require( '@stdlib/array/to-iterator' );
var sin = require( '@stdlib/math/base/special/sin' );

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

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

// ...

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 invoked function is provided one argument:

value: iterated value

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

function fcn( v ) {
    return v + 10;
}

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

var r = it.next().value;
// returns 11

r = it.next().value;
// returns 12

r = it.next().value;
// returns 13

// ...

The function supports the following options:

invalid: return value when an input iterator yields a non-numeric value. Default: NaN.

By default, the function returns an iterator which returns NaN when an input iterator yields a non-numeric value. To specify a different return value, set the invalid option.

var array2iterator = require( '@stdlib/array/to-iterator' );
var sin = require( '@stdlib/math/base/special/sin' );

var opts = {
    'invalid': null
};
var it = iterMap( array2iterator( [ '1', '2', '3' ] ), sin, opts );
// returns <Object>

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

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

// ...

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 sin = require( '@stdlib/math/base/special/sin' );
var iterMap = require( '@stdlib/math/iter/tools/map' );

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

// Create an iterator which consumes the pseudorandom number iterator:
var it = iterMap( rand, sin );

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