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math/round.cpp

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#include "round.h"

#include <math/real.h>

// round(const float value, const int precision)                            //                                                        //

float round(const float value, const int precision)
{
    return (float) round(double(value),precision);
}

// double round(constdouble value, const int precision)                     //

double round(const double value, const int precision)
{
    if (precision>=0) 
    {
        // Prevent excessive precision

        const int p = CLAMP(precision,-15,15);
        
        // Lookup table for pwr(10.0,i)

        const static double pwr[] = { 
                1e0,  1e1,  1e2,  1e3,  1e4, 
                1e5,  1e6,  1e7,  1e8,  1e9, 
                1e10, 1e11, 1e12, 1e13, 1e14 };

        // Table of inverses
        const static double invpwr[] = {
                1e0,   1e-1,  1e-2,  1e-3,  1e-4, 
                1e-5,  1e-6,  1e-7,  1e-8,  1e-9, 
                1e-10, 1e-11, 1e-12, 1e-13, 1e-14 };

        //

        double val = value;

        // 

        if (value<0.0)
            val = ceil(val*pwr[p]-0.5);

        if (value>0.0)
            val = floor(val*pwr[p]+0.5);

        return val*invpwr[p];
    }
    
    // TODO - Precision is negative

    return value;
}

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