rlib/rmath.h

// Written by retoor@molodetz.nl

// This code provides custom implementations of the `ceil`, `floor`, and `modf` functions for double precision numbers that mimic the
// behavior of those found in the C standard math library.

// Summary of used imports: <math.h> for mathematical functions.

// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software
// and associated documentation files (the "Software"), to deal in the Software without restriction,
// including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial
// portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
// NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#ifndef RMATH_H
#define RMATH_H

#include <math.h>

#ifndef ceil
double ceil(double x) {
    if (x == (double)(long long)x) {
        return x;
    } else if (x > 0.0) {
        return (double)(long long)x + 1.0;
    } else {
        return (double)(long long)x;
    }
}
#endif

#ifndef floor
double floor(double x) {
    if (x >= 0.0) {
        return (double)(long long)x;
    } else {
        double result = (double)(long long)x;
        return (result == x) ? result : result - 1.0;
    }
}
#endif

#ifndef modf
double modf(double x, double *iptr) {
    double int_part = (x >= 0.0) ? floor(x) : ceil(x);
    *iptr = int_part;
    return x - int_part;
}
#endif

#endif