Round a numeric value to the nearest multiple of 10^n toward zero.
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> Round a numeric value to the nearest multiple of 10^n toward zero.
``bash`
npm install @stdlib/math-base-special-truncn
`javascript`
var truncn = require( '@stdlib/math-base-special-truncn' );
#### truncn( x, n )
Rounds a numeric value to the nearest multiple of 10^n toward zero.
`javascript
// Round a value to 4 decimal places:
var v = truncn( 3.141592653589793, -4 );
// returns 3.1415
// If n = 0, truncn behaves like trunc:
v = truncn( 3.141592653589793, 0 );
// returns 3.0
// Round a value to the nearest thousand:
v = truncn( 12368.0, 3 );
// returns 12000.0
`
- When operating on [floating-point numbers][ieee754] in bases other than 2, rounding to specified digits can be inexact.
`javascript
var randu = require( '@stdlib/random-base-randu' );
var truncn = require( '@stdlib/math-base-special-truncn' );
var x;
var n;
var v;
var i;
for ( i = 0; i < 100; i++ ) {
x = (randu()*100.0) - 50.0;
n = truncn( randu()*5.0, 0 );
v = truncn( x, -n );
console.log( 'x: %d. Number of decimals: %d. Rounded: %d.', x, n, v );
}
`
*
`c`
#include "stdlib/math/base/special/truncn.h"
#### stdlib_base_truncn( x, n )
Rounds a numeric value to the nearest multiple of 10^n toward zero.
`c`
double y = stdlib_base_truncn( 3.141592653589793, -4 );
// 3.1415
The function accepts the following arguments:
- x: [in] double input value.[in] int32_t
- n: integer power of 10.
`c`
double stdlib_base_truncn( const double x, const int32_t n );
`c
#include "stdlib/math/base/special/truncn.h"
#include
int main( void ) {
const double x[] = { 3.141592653589793, -3.141592653589793, 2.731, 3.55555 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_truncn( x[ i ], -2 );
printf( "truncn(%lf) = %lf\n", x[ i ], y );
}
}
`
*
- [@stdlib/math-base/special/ceiln][@stdlib/math/base/special/ceiln]: round a numeric value to the nearest multiple of 10^n toward positive infinity.
- [@stdlib/math-base/special/floorn][@stdlib/math/base/special/floorn]: round a double-precision floating-point number to the nearest multiple of 10^n toward negative infinity.
- [@stdlib/math-base/special/roundn][@stdlib/math/base/special/roundn]: round a double-precision floating-point number to the nearest multiple of 10^n.
- [@stdlib/math-base/special/trunc][@stdlib/math/base/special/trunc]: round a double-precision floating-point number toward zero.
- [@stdlib/math-base/special/truncb][@stdlib/math/base/special/truncb]: round a numeric value to the nearest multiple of b^n 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-truncn/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-truncn/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-truncn/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-truncn/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-truncn/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-truncn/blob/esm/README.md
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-truncn/main/LICENSE
[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
[@stdlib/math/base/special/ceiln]: https://www.npmjs.com/package/@stdlib/math-base-special-ceiln
[@stdlib/math/base/special/floorn]: https://www.npmjs.com/package/@stdlib/math-base-special-floorn
[@stdlib/math/base/special/roundn]: https://www.npmjs.com/package/@stdlib/math-base-special-roundn
[@stdlib/math/base/special/trunc]: https://www.npmjs.com/package/@stdlib/math-base-special-trunc
[@stdlib/math/base/special/truncb]: https://www.npmjs.com/package/@stdlib/math-base-special-truncb