floorn

Round a double-precision floating-point number to the nearest multiple of 10^n toward negative infinity.

Usage

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

floorn( x, n )

Rounds a double-precision floating-point number to the nearest multiple of 10^n toward negative infinity.

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

// If n = 0, `floorn` behaves like `floor`:
v = floorn( 3.141592653589793, 0 );
// returns 3.0

// Round a value to the nearest thousand:
v = floorn( 12368.0, 3 );
// returns 12000.0

Notes

When operating on floating-point numbers in bases other than 2, rounding to specified digits can be inexact. For example,

var x = -0.2 - 0.1;
// returns -0.30000000000000004

// Should round to -0.3:
var v = floorn( x, -16 );
// returns -0.3000000000000001

Examples

var randu = require( '@stdlib/random/base/randu' );
var floorn = require( '@stdlib/math/base/special/floorn' );

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

for ( i = 0; i < 100; i++ ) {
    x = (randu()*100.0) - 50.0;
    n = floorn( randu()*5.0, 0 );
    v = floorn( x, -n );
    console.log( 'x: %d. Number of decimals: %d. Rounded: %d.', x, n, v );
}

C APIs

Usage

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

stdlib_base_floorn( x, n )

Rounds a double-precision floating-point number to the nearest multiple of 10^n toward negative infinity.

double y = stdlib_base_floorn( 3.141592653589793, -4 );
// returns 3.1415

// If n = 0, `floorn` behaves like `floor`:
double y = stdlib_base_floorn( 3.141592653589793, 0 );
// returns 3.0

The function accepts the following arguments:

x: [in] double input value.
n: [in] int32_t integer power of 10.

double stdlib_base_floorn( const double x, const int32_t n );

Examples

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

int main() {
    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_floorn( x[ i ], -2 );
        printf( "floorn(%lf, -2) = %lf\n", x[ i ], y );
    }
}