floorb

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

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 );
    }
}