iterMap2

Create an iterator which invokes a binary function accepting numeric arguments for each iterated value.

Usage

var iterMap2 = require( '@stdlib/math/iter/tools/map2' );

iterMap2( iter0, iter1, fcn[, options] )

Returns an iterator which invokes a binary function accepting numeric arguments for each iterated value.

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

var it1 = array2iterator( [ 1.0, 2.0, 3.0, 4.0 ] );
var it2 = array2iterator( [ 1.0, -1.0, -1.0, 1.0 ] );

var it = iterMap2( it1, it2, copysign );
// returns <Object>

var r = it.next().value;
// returns 1.0

r = it.next().value;
// returns -2.0

r = it.next().value;
// returns -3.0

// ...

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 two arguments:

x: iterated value from first input iterator.
y: iterated value from second input iterator.

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

function fcn( x, y ) {
    return x + y + 10;
}

var it1 = array2iterator( [ 1, 2, 3, 4 ] );
var it2 = array2iterator( [ 1, 2, 3, 4 ] );

var it = iterMap2( it1, it2, fcn );
// returns <Object>

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

r = it.next().value;
// returns 14

r = it.next().value;
// returns 16

// ...

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 copysign = require( '@stdlib/math/base/special/copysign' );

var it1 = array2iterator( [ '1.0', '2.0', '3.0' ] );
var it2 = array2iterator( [ 1.0, 2.0, 3.0 ] );

var opts = {
    'invalid': null
};
var it = iterMap2( it1, it2, copysign, opts );
// returns <Object>

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

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

// ...

If provided a numeric value as an iterator argument, the value is broadcast as an infinite iterator which always returns the provided value.

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

var it1 = array2iterator( [ 1.0, 2.0 ] );

var it = iterMap2( it1, -4.0, copysign );
// returns <Object>

var v = it.next().value;
// returns -1.0

v = it.next().value;
// returns -2.0

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

Notes

If an iterated value is non-numeric (including NaN), the returned iterator returns NaN. If non-numeric iterated values are possible, you are advised to provide an iterator which type checks and handles non-numeric values accordingly.
The length of the returned iterator is equal to the length of the shortest provided iterator. In other words, the returned iterator ends once one of the provided iterators ends.
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 uniform = require( '@stdlib/random/iter/uniform' );
var copysign = require( '@stdlib/math/base/special/copysign' );
var iterMap2 = require( '@stdlib/math/iter/tools/map2' );

// Create seeded iterators for generating pseudorandom numbers:
var rand1 = randu({
    'seed': 1234,
    'iter': 10
});

var rand2 = uniform( -1.0, 1.0, {
    'seed': 1234,
    'iter': 10
});

// Create an iterator which consumes the pseudorandom number iterators:
var it = iterMap2( rand1, rand2, copysign );

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