time-to-botec

README.md (6736B)

---

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 # iterMap2
 
 > Create an [iterator][mdn-iterator-protocol] which invokes a binary function accepting numeric arguments for each iterated value.
 
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 <section class="intro">
 
 </section>
 
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 <!-- Package usage documentation. -->
 
 <section class="usage">
 
 ## Usage
 
 ```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 <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][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 <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][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 <Object>
 
 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 <Object>
 
 var v = it.next().value;
 // returns -1.0
 
 v = it.next().value;
 // returns -2.0
 
 var bool = it.next().done;
 // returns true
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
 
 <section class="notes">
 
 ## Notes
 
 -   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.
 -   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 `Symbol.iterator` **and** a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.
 
 </section>
 
 <!-- /.notes -->
 
 <!-- Package usage examples. -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```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 );
 }
 ```
 
 </section>
 
 <!-- /.examples -->
 
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 <section class="links">
 
 [mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
 
 </section>
 
 <!-- /.links -->