@stdlib/math-base-special-truncb

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truncb

Round a numeric value to the nearest multiple of b^n toward zero.

Installation

npm install @stdlib/math-base-special-truncb

Usage

var truncb = require( '@stdlib/math-base-special-truncb' );

truncb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n toward zero.

// Round a value to 4 decimal places:
var v = truncb( 3.141592653589793, -4, 10 );
// returns 3.1415

// If n = 0 or b = 1, `truncb` behaves like `trunc`:
v = truncb( 3.141592653589793, 0, 2 );
// returns 3.0

// Round a value to the nearest multiple of two toward zero:
v = truncb( 5.0, 1, 2 );
// returns 4.0

Notes

• Due to rounding error in floating-point numbers, rounding may not be exact.

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var pow = require( '@stdlib/math-base-special-pow' );
var truncb = require( '@stdlib/math-base-special-truncb' );

var x;
var n;
var b;
var v;
var i;

for ( i = 0; i < 100; i++ ) {
    x = (randu()*100.0) - 50.0;
    n = round( (randu()*10.0) - 5.0 );
    b = round( randu()*10.0 );
    v = truncb( x, n, b );
    console.log( 'x: %d. %d^%d: %d. Rounded: %d.', x, b, n, pow( b, n ), v );
}

C APIs

Usage

#include "stdlib/math/base/special/truncb.h"

stdlib_base_truncb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n toward zero.

double out = stdlib_base_truncb( 3.141592653589793, -4, 10 );
// returns 3.1415

The function accepts the following arguments:

• x: [in] double input value.
• n: [in] int32_t power.
• b: [in] int32_t base.

double stdlib_base_truncb( const double x, const int32_t n, const int32_t b );

Examples

#include "stdlib/math/base/special/truncb.h"
#include <stdio.h>
#include <stdint.h>

int main( void ) {
    const double x[] = { -5.0, -3.89, -2.78, -1.67, -0.56, 0.56, 1.67, 2.78, 3.89, 5.0 };
    const int32_t n[] = { -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 };
    const int32_t b[] = { 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 };

    double v;
    int i;
    for ( i = 0; i < 10; i++ ) {
        v = stdlib_base_truncb( x[ i ], n[ i ], b[ i ] );
        printf( "truncb(%lf, %d, %d) = %lf\n", x[ i ], n[ i ], b[ i ], v );
    }
}

See Also

• @stdlib/math-base/special/ceilb: round a numeric value to the nearest multiple of b^n toward positive infinity.
• @stdlib/math-base/special/floorb: round a numeric value to the nearest multiple of b^n toward negative infinity.
• @stdlib/math-base/special/roundb: round a numeric value to the nearest multiple of b^n on a linear scale.
• @stdlib/math-base/special/trunc: round a double-precision floating-point number toward zero.
• @stdlib/math-base/special/truncn: round a numeric value to the nearest multiple of 10^n toward zero.

Notice

This package is part of 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, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.