Create an iterator which invokes a binary function accepting numeric arguments for each iterated value.
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> Create an [iterator][mdn-iterator-protocol] which invokes a binary function accepting numeric arguments for each iterated value.
``bash`
npm install @stdlib/math-iter-tools-map2
`javascript`
var iterMap2 = require( '@stdlib/math-iter-tools-map2' );
#### iterMap2( iter0, iter1, fcn\[, options] )
Returns an [iterator][mdn-iterator-protocol] which invokes a binary function accepting numeric arguments for each iterated value.
`javascript
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
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][mdn-iterator-protocol] protocol-compliant object has the following properties:
- next: function which returns an [iterator][mdn-iterator-protocol] 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][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.
The invoked function is provided two arguments:
- x: iterated value from first input [iterator][mdn-iterator-protocol].y
- : iterated value from second input [iterator][mdn-iterator-protocol].
`javascript
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
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][mdn-iterator-protocol] yields a non-numeric value. Default: NaN.
By default, the function returns an [iterator][mdn-iterator-protocol] which returns NaN when an input [iterator][mdn-iterator-protocol] yields a non-numeric value. To specify a different return value, set the invalid option.
`javascript
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
var v = it.next().value;
// returns null
v = it.next().value;
// returns null
// ...
`
If provided a numeric value as an [iterator][mdn-iterator-protocol] argument, the value is broadcast as an infinite [iterator][mdn-iterator-protocol] which always returns the provided value.
`javascript
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
var v = it.next().value;
// returns -1.0
v = it.next().value;
// returns -2.0
var bool = it.next().done;
// returns true
`
- If an iterated value is non-numeric (including NaN), the returned [iterator][mdn-iterator-protocol] returns NaN. If non-numeric iterated values are possible, you are advised to provide an [iterator][mdn-iterator-protocol] which type checks and handles non-numeric values accordingly.Symbol.iterator
- The length of the returned [iterator][mdn-iterator-protocol] is equal to the length of the shortest provided [iterator][mdn-iterator-protocol]. In other words, the returned [iterator][mdn-iterator-protocol] ends once one of the provided [iterators][mdn-iterator-protocol] ends.
- If an environment supports and a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.
`javascript
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 );
}
`
*
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol