time-to-botec/squiggle/node_modules/@stdlib/math/iter/ops/subtract/README.md

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# iterSubtract

> Create an [iterator][mdn-iterator-protocol] which performs element-wise subtraction of two or more [iterators][mdn-iterator-protocol].

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## Usage

```javascript
var iterSubtract = require( '@stdlib/math/iter/ops/subtract' );
```

#### iterSubtract( iter0, ...iterator )

Returns an [iterator][mdn-iterator-protocol] which performs element-wise subtraction of two or more [iterators][mdn-iterator-protocol].

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

var it1 = array2iterator( [ 1.0, 5.0 ] );
var it2 = array2iterator( [ 3.0, 4.0 ] );

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

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

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

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

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][mdn-iterator-protocol] 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.

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 arr = array2iterator( [ 1.0, 2.0 ] );

var it = iterSubtract( arr, 4.0 );
// returns <Object>

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

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

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

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## 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** provided [iterators][mdn-iterator-protocol] are iterable, the returned [iterator][mdn-iterator-protocol] is iterable.

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
var iterSineWave = require( '@stdlib/simulate/iter/sine-wave' );
var iterSubtract = require( '@stdlib/math/iter/ops/subtract' );

// Create an iterator which generates a sine wave:
var sine1 = iterSineWave({
    'period': 50,
    'offset': 0,
    'iter': 100
});

// Create another iterator which generates a higher frequency sine wave:
var sine2 = iterSineWave({
    'period': 10,
    'offset': 0,
    'iter': 100
});

// Create an iterator which subtracts the two waveforms:
var it = iterSubtract( sine1, sine2 );

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

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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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