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Original file line number Diff line number Diff line change
@@ -0,0 +1,136 @@
<!--

@license Apache-2.0

Copyright (c) 2026 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

-->

# isAlmostSameValue

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

<section class="usage">

## Usage

```javascript
var isAlmostSameValue = require( '@stdlib/number/float16/base/assert/is-almost-same-value' );
```

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

Tests if two half-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/float16/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/float16/eps' );
var isAlmostSameValue = require( '@stdlib/number/float16/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
```
Comment on lines +87 to +114
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Suggested change
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
```
var bool = isAlmostSameValue( 1.0, 1.0+EPS, 1 );
// returns true
bool = isAlmostSameValue( 1.0+EPS, 1.0, 1 );
// returns true
bool = isAlmostSameValue( 1.0, 1.0+EPS+EPS, 1 );
// returns false
bool = isAlmostSameValue( 1.0, 1.0+EPS, 0 );
// returns false
bool = isAlmostSameValue( -0.0, 0.0, 0 );
// returns false
bool = isAlmostSameValue( 1.0, NaN, 1 );
// returns false
bool = isAlmostSameValue( NaN, NaN, 1 );
// returns true

Let's remove the console.log in the markdown.

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</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

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

</section>

<!-- /.links -->
Original file line number Diff line number Diff line change
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/**
* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var bench = require( '@stdlib/bench' );
var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
var pkg = require( './../package.json' ).name;
var isAlmostSameValue = require( './../lib' );


// MAIN //

bench( pkg, function benchmark( b ) {
var values;
var bool;
var v;
var i;

values = [
5.0,
3.14,
NaN,
-0.0,
0.0,
-1.0
];

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
v = values[ i%values.length ];
bool = isAlmostSameValue( v, v, 1 );
if ( typeof bool !== 'boolean' ) {
b.fail( 'should return a boolean' );
}
}
b.toc();
if ( !isBoolean( bool ) ) {
b.fail( 'should return a boolean' );
}
b.pass( 'benchmark finished' );
b.end();
});
Original file line number Diff line number Diff line change
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{{alias}}( a, b, maxULP )
Tests if two half-precision floating-point numbers are approximately the
same value within a specified number of ULPs (units in the last place).

The function differs from the `===` operator in that the function treats
`-0` and `+0` as distinct and `NaNs` as the same.

Parameters
----------
a: number
First input value.

b: number
Second input value.

maxULP: number
Maximum allowed ULP difference.

Returns
-------
bool: boolean
Boolean indicating whether two half-precision floating-point numbers
are approximately the same value within a specified number of ULPs.

Examples
--------
> var bool = {{alias}}( 1, 1+{{alias:@stdlib/constants/float16/eps}}, 1 )
true
> bool = {{alias}}( 1+{{alias:@stdlib/constants/float16/eps}}, 1, 1 )
true
> bool = {{alias}}( 1, 1+{{alias:@stdlib/constants/float16/eps}}*2, 1 )
false
> bool = {{alias}}( 0.0, -0.0, 0 )
false
> bool = {{alias}}( NaN, 1.0, 1 )
false
> bool = {{alias}}( NaN, NaN, 0 )
true

See Also
--------

Original file line number Diff line number Diff line change
@@ -0,0 +1,62 @@
/*
* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

// TypeScript Version: 4.1

/**
* Tests if two half-precision floating-point numbers are approximately the same value within a specified number of ULPs (units in the last place).
*
* ## Notes
*
* - The function differs from the `===` operator in that the function treats `-0` and `+0` as distinct and `NaNs` as the same.
*
* @param a - first input value
* @param b - second input value
* @param maxULP - maximum allowed ULP difference
* @returns boolean indicating whether two half-precision floating-point numbers are approximately the same value within a specified number of ULPs
*
* @example
* var EPS = require( '@stdlib/constants/float16/eps' );
*
* var bool = isAlmostSameValue( 1.0, 1.0+EPS, 1 );
* // returns true
*
* bool = isAlmostSameValue( 1.0+EPS, 1.0, 1 );
* // returns true
*
* bool = isAlmostSameValue( 1.0, 1.0+EPS+EPS, 1 );
* // returns false
*
* bool = isAlmostSameValue( 1.0, 1.0+EPS, 0 );
* // returns false
*
* bool = isAlmostSameValue( 0.0, -0.0, 0 );
* // returns false
*
* bool = isAlmostSameValue( 1.0, NaN, 1 );
* // returns false
*
* bool = isAlmostSameValue( NaN, NaN, 1 );
* // returns true
*/
declare function isAlmostSameValue( a: number, b: number, maxULP: number ): boolean;


// EXPORTS //

export = isAlmostSameValue;
Original file line number Diff line number Diff line change
@@ -0,0 +1,71 @@
/*
* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import isAlmostSameValue = require( './index' );


// TESTS //

// The function returns a boolean...
{
isAlmostSameValue( 3.14, 3.14, 1 ); // $ExpectType boolean
}

// The compiler throws an error if the function is not provided a first argument which is a number...
{
isAlmostSameValue( '5', 3.14, 1 ); // $ExpectError
isAlmostSameValue( true, 3.14, 1 ); // $ExpectError
isAlmostSameValue( false, 3.14, 1 ); // $ExpectError
isAlmostSameValue( null, 3.14, 1 ); // $ExpectError
isAlmostSameValue( void 0, 3.14, 1 ); // $ExpectError
isAlmostSameValue( [], 3.14, 1 ); // $ExpectError
isAlmostSameValue( {}, 3.14, 1 ); // $ExpectError
isAlmostSameValue( ( x: number ): number => x, 3.14, 1 ); // $ExpectError
}

// The compiler throws an error if the function is not provided a second argument which is a number...
{
isAlmostSameValue( 3.14, '5', 1 ); // $ExpectError
isAlmostSameValue( 3.14, true, 1 ); // $ExpectError
isAlmostSameValue( 3.14, false, 1 ); // $ExpectError
isAlmostSameValue( 3.14, null, 1 ); // $ExpectError
isAlmostSameValue( 3.14, void 0, 1 ); // $ExpectError
isAlmostSameValue( 3.14, [], 1 ); // $ExpectError
isAlmostSameValue( 3.14, {}, 1 ); // $ExpectError
isAlmostSameValue( 3.14, ( x: number ): number => x, 1 ); // $ExpectError
}

// The compiler throws an error if the function is not provided a third argument which is a number...
{
isAlmostSameValue( 3.14, 3.14, '5' ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, true ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, false ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, null ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, void 0 ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, [] ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, {} ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, ( x: number ): number => x ); // $ExpectError
}

// The compiler throws an error if the function is provided an unsupported number of arguments...
{
isAlmostSameValue(); // $ExpectError
isAlmostSameValue( 3.14 ); // $ExpectError
isAlmostSameValue( 3.14, 3.14 ); // $ExpectError
isAlmostSameValue( 3.14, 3.14, 1, 2 ); // $ExpectError
}
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