/* -*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*- */
/* vim: set filetype=c tabstop=8 shiftwidth=4 expandtab: */

/*
    round.d  -- Implementation of CL:ROUND
*/
/*
    Copyright (c) 2010, Juan Jose Garcia Ripoll.

    ECL is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    See file '../../Copyright' for full details.
*/

#define ECL_INCLUDE_MATH_H
#include <ecl/ecl.h>
#include <float.h>
#include <ecl/ecl.h>
#include <ecl/impl/math_dispatch2.h>
#ifndef HAVE_ISOC99
# define floorf floor
#endif
#include <ecl/internal.h>

@(defun round (x &optional (y OBJNULL))
@
        if (narg == 1)
                return ecl_round1(x);
        else
                return ecl_round2(x, y);
@)

static cl_object
number_remainder(cl_object x, cl_object y, cl_object q)
{
        cl_object z;

        z = ecl_times(q, y);
        z = ecl_minus(x, z);
        return(z);
}

static double
round_double(double d)
{
        if (d >= 0) {
                double q = floor(d += 0.5);
                if (q == d) {
                        int i = (int)fmod(q, 10);
                        if (i & 1) {
                                return q-1;
                        }
                }
                return q;
        } else {
                return -round_double(-d);
        }
}

#ifdef ECL_LONG_FLOAT
static long double
round_long_double(long double d)
{
        if (d >= 0) {
                long double q = floorl(d += 0.5);
                if (q == d) {
                        int i = (int)fmodl(q, 10);
                        if (i & 1) {
                                return q-1;
                        }
                }
                return q;
        } else {
                return -round_long_double(-d);
        }
}
#endif

static cl_object
ecl_round2_integer(const cl_env_ptr the_env, cl_object x, cl_object y, cl_object q)
{
        cl_object q1 = ecl_integer_divide(q->ratio.num, q->ratio.den);
        cl_object r = ecl_minus(q, q1);
        if (ecl_minusp(r)) {
                int c = ecl_number_compare(cl_core.minus_half, r);
                if (c > 0 || (c == 0 && ecl_oddp(q1))) {
                        q1 = ecl_one_minus(q1);
                }
        } else {
                int c = ecl_number_compare(r, cl_core.plus_half);
                if (c > 0 || (c == 0 && ecl_oddp(q1))) {
                        q1 = ecl_one_plus(q1);
                }
        }
        r = number_remainder(x, y, q1);
        ecl_return2(the_env, q1, r);
}

cl_object
ecl_round1(cl_object x)
{
        const cl_env_ptr the_env = ecl_process_env();
        cl_object v0, v1;
        switch (ecl_t_of(x)) {
        case t_fixnum:
        case t_bignum:
                v0 = x;
                v1 = ecl_make_fixnum(0);
                break;
        case t_ratio:
                v0 = ecl_round2_integer(the_env, x->ratio.num, x->ratio.den, x);
                v1 = ecl_make_ratio(ecl_nth_value(the_env, 1), x->ratio.den);
                break;
        case t_singlefloat: {
                float d = ecl_single_float(x);
                float q = round_double(d);
                v0 = _ecl_float_to_integer(q);
                v1 = ecl_make_single_float(d - q);
                break;
        }
        case t_doublefloat: {
                double d = ecl_double_float(x);
                double q = round_double(d);
                v0 = _ecl_double_to_integer(q);
                v1 = ecl_make_double_float(d - q);
                break;
        }
#ifdef ECL_LONG_FLOAT
        case t_longfloat: {
                long double d = ecl_long_float(x);
                long double q = round_long_double(d);
                v0 = _ecl_long_double_to_integer(q);
                v1 = ecl_make_long_float(d - q);
                break;
        }
#endif
        default:
                FEwrong_type_nth_arg(@[round],1,x,@[real]);
        }
        ecl_return2(the_env, v0, v1);
}

cl_object
ecl_round2(cl_object x, cl_object y)
{
        const cl_env_ptr the_env = ecl_process_env();
        cl_object v0, v1;
        cl_object q;

        q = ecl_divide(x, y);
        switch (ecl_t_of(q)) {
        case t_fixnum:
        case t_bignum:
                v0 = q;
                v1 = ecl_make_fixnum(0);
                break;
        case t_ratio:
                return ecl_round2_integer(the_env, x, y, q);
        default:
                v0 = q = ecl_round1(q);
                v1 = number_remainder(x, y, q);
        }
        ecl_return2(the_env, v0, v1);
}
