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# Float16 [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] > 16-bit half-precision floating-point number.
## Installation ```bash npm install @stdlib/number-float16-ctor ```
## 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 ``` * * * ## 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 ```
* * *
## 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.
* * *
## Examples ```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}' ```
* * *
## C APIs
### 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 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 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.
### 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.
### Examples ```c #include "stdlib/number/float16/ctor.h" #include #include 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 ] ) ); } } ```
* * * ## 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 © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/number-float16-ctor.svg [npm-url]: https://npmjs.org/package/@stdlib/number-float16-ctor [test-image]: https://github.com/stdlib-js/number-float16-ctor/actions/workflows/test.yml/badge.svg?branch=v0.1.2 [test-url]: https://github.com/stdlib-js/number-float16-ctor/actions/workflows/test.yml?query=branch:v0.1.2 [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/number-float16-ctor/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/number-float16-ctor?branch=main [chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg [chat-url]: https://stdlib.zulipchat.com [stdlib]: https://github.com/stdlib-js/stdlib [stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors [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-float16-ctor/tree/deno [deno-readme]: https://github.com/stdlib-js/number-float16-ctor/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/number-float16-ctor/tree/umd [umd-readme]: https://github.com/stdlib-js/number-float16-ctor/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/number-float16-ctor/tree/esm [esm-readme]: https://github.com/stdlib-js/number-float16-ctor/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/number-float16-ctor/blob/main/branches.md [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 [mdn-json-parse]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse [@stdlib/number/float16/reviver]: https://www.npmjs.com/package/@stdlib/number-float16-reviver