/* -*- Mode: C; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/* vim: set filetype=c tabstop=2 shiftwidth=2 expandtab: */

/*
 * round.d - implementation of CL:ROUND
 *
 * Copyright (c) 1984 Taiichi Yuasa and Masami Hagiya
 * Copyright (c) 1990 Giuseppe Attardi
 * Copyright (c) 2001 Juan Jose Garcia Ripoll
 *
 * See file 'LICENSE' for the copyright 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>

#pragma STDC FENV_ACCESS ON

@(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 if (isnan(d)) {
    return d;
  } else {
    return -round_double(-d);
  }
}

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 if (isnan(d)) {
    return d;
  } else {
    return -round_long_double(-d);
  }
}

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;
  ECL_MATHERR_CLEAR;

  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;
  }
  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;
  }
  default:
    FEwrong_type_nth_arg(@[round],1,x,@[real]);
  }

  ECL_MATHERR_TEST;
  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);
}
