Create an iterator which invokes a unary function accepting a single numeric argument for each iterated value.
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> Create an [iterator][mdn-iterator-protocol] which invokes a unary function accepting a single numeric argument for each iterated value.
``bash`
npm install @stdlib/math-iter-tools-map
`javascript`
var iterMap = require( '@stdlib/math-iter-tools-map' );
#### iterMap( iterator, fcn\[, options] )
Returns an [iterator][mdn-iterator-protocol] which invokes a unary function accepting a single numeric argument for each iterated value.
`javascript
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
var r = it.next().value;
// returns
r = it.next().value;
// returns
r = it.next().value;
// returns
// ...
`
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 one argument:
- value: iterated value.
`javascript
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
return v + 10;
}
var it = iterMap( array2iterator( [ 1, 2, 3, 4 ] ), fcn );
// returns
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][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 sin = require( '@stdlib/math-base-special-sin' );
var opts = {
'invalid': null
};
var it = iterMap( array2iterator( [ '1', '2', '3' ] ), sin, opts );
// returns
var v = it.next().value;
// returns null
v = it.next().value;
// returns null
// ...
`
- If an environment supports Symbol.iterator 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 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 );
}
`
*
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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---
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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol