npm package: @stdlib/number-float16-ctor
Description: 16-bit half-precision floating-point number.
Author: The Stdlib Authors
Latest version: 0.1.2

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<details>
  <summary>
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# Float16

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

> 16-bit half-precision floating-point number.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/number-float16-ctor
```

</section>

<section class="usage">

## Usage

```javascript
var Float16 = require( '@stdlib/number-float16-ctor' );
```

#### Float16( value )

16-bit half-precision floating-point number constructor.

```javascript
var x = new Float16( 5.0 );
// returns <Float16>
```

* * *

## Properties

#### Float16.name

Static property returning the constructor name.

```javascript
var str = Float16.name;
// returns 'Float16'
```

#### Float16.BYTES_PER_ELEMENT

Size (in bytes) of the underlying value.

```javascript
var nbytes = Float16.BYTES_PER_ELEMENT;
// returns 2
```

#### Float16.prototype.BYTES_PER_ELEMENT

Size (in bytes) of the underlying value.

```javascript
var x = new Float16( 5.0 );

var nbytes = x.BYTES_PER_ELEMENT;
// returns 2
```

### Instance

A `Float16` instance has the following properties...

#### value

A **read-only** property returning the underlying value as a number.

```javascript
var x = new Float16( 5.0 );

var v = x.value;
// returns 5.0
```

* * *

## Methods

### Accessor Methods

These methods do **not** mutate a `Float16` instance and, instead return a half-precision floating-point number representation.

#### Float16.prototype.toString()

Returns a string representation of a `Float16` instance.

```javascript
var x = new Float16( 5.0 );
var str = x.toString();
// returns '5'

x = new Float16( -3.14 );
str = x.toString();
// returns '-3.140625'
```

#### Float16.prototype.toJSON()

Returns a [JSON][json] representation of a `Float16` instance. [`JSON.stringify()`][mdn-json-stringify] implicitly calls this method when stringifying a `Float16` instance.

```javascript
var x = new Float16( 5.0 );

var o = x.toJSON();
/*
  {
    "type": "Float16",
    "value": 5.0
  }
*/
```

To [revive][mdn-json-parse] a `Float16` number from a [JSON][json] `string`, see [@stdlib/number/float16/reviver][@stdlib/number/float16/reviver].

#### Float16.prototype.valueOf()

Converts a `Float16` instance to a primitive value.

```javascript
var x = new Float16( 5.0 );
var v = x.valueOf();
// returns 5.0

x = new Float16( 3.14 );
v = x.valueOf();
// returns 3.140625
```

</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

-   The underlying value is stored as a half-precision floating-point number [IEEE 754][ieee754] with 1 sign bit, 5 exponent bits, and 10 significand bits.
-   A half-precision floating-point number has a range of approximately `±6.55e4` and a precision of about 3-4 decimal digits.

</section>

<!-- /.notes -->

* * *

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var Float16 = require( '@stdlib/number-float16-ctor' );

var x = new Float16( 3.14 );

console.log( 'type: %s', typeof x );
// => 'type: object'

console.log( 'str: %s', x );
// => 'str: 3.140625'

console.log( 'value: %d', x.value );
// => 'value: 3.140625'

console.log( 'JSON: %s', JSON.stringify( x ) );
// => 'JSON: {"type":"Float16","value":3.140625}'
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/number/float16/ctor.h"
```

#### stdlib_float16_t

An opaque type definition for a half-precision floating-point number.

```c
stdlib_float16_t v = stdlib_float16_from_bits( 51648 );
```

#### stdlib_float16_bits_t

An opaque type definition for a union for accessing the underlying binary representation of a half-precision floating-point number.

```c
#include <stdint.h>

stdlib_float16_t x = stdlib_float16_from_bits( 51648 );

stdlib_float16_bits_t y;
y.value = x;

uint16_t bits = y.bits;
// returns 51648
```

The union has the following members:

-   **value**: `stdlib_float16_t` half-precision floating-point number.
-   **bits**: `uint16_t` binary representation.

The union allows "type punning"; however, while (more or less) defined in C99, behavior is implementation-defined in C++. For more robust conversion, prefer using explicit helpers for converting to and from binary representation.

#### stdlib_float16_from_bits( bits )

Converts a 16-bit binary representation to a half-precision floating-point number.

```c
stdlib_float16_t v = stdlib_float16_from_bits( 51648 ); // => -11.5
```

The function accepts the following arguments:

-   **bits**: `[in] uint16_t` 16-bit integer corresponding to a binary representation.

#### stdlib_float16_to_bits( x )

Converts a half-precision floating-point number to a 16-bit binary representation.

```c
#include <stdint.h>

stdlib_float16_t v = stdlib_float16_from_bits( 51648 ); // => -11.5

uint16_t bits = stdlib_float16_to_bits( v );
```

The function accepts the following arguments:

-   **x**: `[in] stdlib_float16_t` half-precision floating-point number.

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

### Notes

-   The `stdlib_float16_t` type should be treated as a storage and interchange type. Native hardware support for mathematical functions operating on half-precision floating-point numbers varies. As a consequence, for most operations, one should first promote to single-precision (i.e., `float`), perform the desired operation, and then downcast back to half-precision.

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/number/float16/ctor.h"
#include <stdint.h>
#include <stdio.h>

int main( void ) {
  const stdlib_float16_t x[] = {
    stdlib_float16_from_bits( 51648 ), // -11.5
    stdlib_float16_from_bits( 18880 )  // 11.5
  };

  int i;
  for ( i = 0; i < 2; i++ ) {
    printf( "%d\n", stdlib_float16_to_bits( x[ i ] ) );
  }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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<section class="references">

</section>

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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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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/number-float16-ctor/main/LICENSE

[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985

[json]: http://www.json.org/

[mdn-json-stringify]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify

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[@stdlib/number/float16/reviver]: https://www.npmjs.com/package/@stdlib/number-float16-reviver

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