floorb

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

Installation

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

Usage

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

floorb( x, n, b )

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

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

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

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

Notes

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

  var x = -0.2 - 0.1;
  // returns -0.30000000000000004
  
  // Should round to -0.3...
  var v = floorb( x, -16, 10 );
  // returns -0.3000000000000001

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

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 = floorb( x, n, b );
    console.log( 'x: %d. %d^%d: %d. Rounded: %d.', x, b, n, pow( b, n ), v );
}

Usage

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

stdlib_base_floorb( x, n, b )

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

double out = stdlib_base_floorb( 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_floorb( const double x, const int32_t n, const int32_t b );

Examples

#include "stdlib/math/base/special/floorb.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_floorb( x[ i ], n[ i ], b[ i ] );
        printf( "floorb(%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/floor: round a double-precision floating-point number toward negative infinity.
• @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/roundb: round a numeric value to the nearest multiple of b^n on a linear scale.

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 © 2016-2024. The Stdlib Authors.