Round a numeric value to the nearest power of two toward zero.
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> Round a numeric value to the nearest power of two toward zero.
``bash`
npm install @stdlib/math-base-special-trunc2
`javascript`
var trunc2 = require( '@stdlib/math-base-special-trunc2' );
#### trunc2( x )
Rounds a numeric value to the nearest power of two toward zero.
`javascript
var v = trunc2( -4.2 );
// returns -4.0
v = trunc2( -4.5 );
// returns -4.0
v = trunc2( -4.6 );
// returns -4.0
v = trunc2( 9.99999 );
// returns 8.0
v = trunc2( 9.5 );
// returns 8.0
v = trunc2( 13.0 );
// returns 8.0
v = trunc2( -13.0 );
// returns -8.0
v = trunc2( 0.0 );
// returns 0.0
v = trunc2( -0.0 );
// returns -0.0
v = trunc2( Infinity );
// returns Infinity
v = trunc2( -Infinity );
// returns -Infinity
v = trunc2( NaN );
// returns NaN
`
`javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var trunc2 = require( '@stdlib/math-base-special-trunc2' );
var opts = {
'dtype': 'float64'
};
var x = uniform( 100, -50.0, 50.0, opts );
logEachMap( 'x: %0.4f. Rounded: %0.4f.', x, trunc2 );
`
*
`c`
#include "stdlib/math/base/special/trunc2.h"
#### stdlib_base_trunc2( x )
Rounds a numeric value to the nearest power of two toward zero.
`c`
double y = stdlib_base_trunc2( -4.2 );
// returns -4.0
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_trunc2( const double x );
`c
#include "stdlib/math/base/special/trunc2.h"
#include
int main( void ) {
const double x[] = { 3.14, -3.14, 0.0, 0.0 / 0.0 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_trunc2( x[ i ] );
printf( "trunc2(%lf) = %lf\n", x[ i ], y );
}
}
`
*
- [@stdlib/math-base/special/ceil2][@stdlib/math/base/special/ceil2]: round a numeric value to the nearest power of two toward positive infinity.
- [@stdlib/math-base/special/floor2][@stdlib/math/base/special/floor2]: round a numeric value to the nearest power of two toward negative infinity.
- [@stdlib/math-base/special/round2][@stdlib/math/base/special/round2]: round a numeric value to the nearest power of two on a linear scale.
- [@stdlib/math-base/special/trunc][@stdlib/math/base/special/trunc]: round a double-precision floating-point number toward zero.
- [@stdlib/math-base/special/trunc10][@stdlib/math/base/special/trunc10]: round a numeric value to the nearest power of 10 toward zero.
*
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].
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---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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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/math-base-special-trunc2/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-trunc2/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-trunc2/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-trunc2/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-trunc2/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-trunc2/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-base-special-trunc2/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-trunc2/main/LICENSE
[@stdlib/math/base/special/ceil2]: https://www.npmjs.com/package/@stdlib/math-base-special-ceil2
[@stdlib/math/base/special/floor2]: https://www.npmjs.com/package/@stdlib/math-base-special-floor2
[@stdlib/math/base/special/round2]: https://www.npmjs.com/package/@stdlib/math-base-special-round2
[@stdlib/math/base/special/trunc]: https://www.npmjs.com/package/@stdlib/math-base-special-trunc
[@stdlib/math/base/special/trunc10]: https://www.npmjs.com/package/@stdlib/math-base-special-trunc10