npm package: @stdlib/number-float64-base-assert-is-almost-same-value
Description: Test if two double-precision floating-point numbers are approximately the same value within a specified number of ULPs (units in the last place).
Author: The Stdlib Authors
Latest version: 0.1.1

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# isAlmostSameValue

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Test if two double-precision floating-point numbers are approximately the same value within a specified number of ULPs (units in the last place).

<section class="installation">

## Installation

```bash
npm install @stdlib/number-float64-base-assert-is-almost-same-value
```

</section>

<section class="usage">

## Usage

```javascript
var isAlmostSameValue = require( '@stdlib/number-float64-base-assert-is-almost-same-value' );
```

#### isAlmostSameValue( a, b, maxULP )

Tests if two double-precision floating-point numbers are approximately the same value within a specified number of ULPs (units in the last place).

```javascript
var EPS = require( '@stdlib/constants-float64-eps' );

var bool = isAlmostSameValue( 1.0, 1.0+EPS, 1 );
// returns true

bool = isAlmostSameValue( 1.0, 1.0+EPS, 0 );
// returns false
```

In contrast to the strict equality operator `===`, the function distinguishes between `+0` and `-0` and treats `NaNs` as the same value.

```javascript
var bool = isAlmostSameValue( NaN, 1.0, 1 );
// returns false

bool = isAlmostSameValue( 1.0, NaN, 1 );
// returns false

bool = isAlmostSameValue( NaN, NaN, 1 );
// returns true

bool = isAlmostSameValue( 0.0, -0.0, 0 );
// returns false
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The function implements the [SameValue Algorithm][ecma-262-same-value-algorithm] as specified in ECMAScript 5.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var EPS = require( '@stdlib/constants-float64-eps' );
var isAlmostSameValue = require( '@stdlib/number-float64-base-assert-is-almost-same-value' );

var bool = isAlmostSameValue( 1.0, 1.0+EPS, 1 );
console.log( bool );
// => true

bool = isAlmostSameValue( 1.0+EPS, 1.0, 1 );
console.log( bool );
// => true

bool = isAlmostSameValue( 1.0, 1.0+EPS+EPS, 1 );
console.log( bool );
// => false

bool = isAlmostSameValue( 1.0, 1.0+EPS, 0 );
console.log( bool );
// => false

bool = isAlmostSameValue( -0.0, 0.0, 0 );
console.log( bool );
// => false

bool = isAlmostSameValue( 1.0, NaN, 1 );
console.log( bool );
// => false

bool = isAlmostSameValue( NaN, NaN, 1 );
console.log( bool );
// => true
```

</section>

<!-- /.examples -->

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<section class="related">

</section>

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<section class="main-repo" >

* * *

## Notice

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].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/number-float64-base-assert-is-almost-same-value/main.svg
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/number-float64-base-assert-is-almost-same-value/tree/deno
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[esm-url]: https://github.com/stdlib-js/number-float64-base-assert-is-almost-same-value/tree/esm
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/number-float64-base-assert-is-almost-same-value/main/LICENSE

[ecma-262-same-value-algorithm]: http://ecma-international.org/ecma-262/5.1/#sec-9.12

</section>

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