/* -*-comment-start: "//";comment-end:""-*-
 * Mes --- Maxwell Equations of Software
 * Copyright © 2016,2017,2018 Jan Nieuwenhuizen <janneke@gnu.org>
 *
 * This file is part of Mes.
 *
 * Mes is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * Mes is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Mes.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <limits.h>

void
assert_number (char const* name, SCM x)
{
  if (TYPE (x) != TNUMBER)
    {
      eputs (name);
      error (cell_symbol_not_a_number, x);
    }
}

SCM
greater_p (SCM x) ///((name . ">") (arity . n))
{
  int n = INT_MAX;
  while (x != cell_nil)
    {
      assert_number ("greater_p", CAR (x));
      if (VALUE (car (x)) >= n)
        return cell_f;
      n = VALUE (car (x));
      x = cdr (x);
    }
  return cell_t;
}

SCM
less_p (SCM x) ///((name . "<") (arity . n))
{
  int n = INT_MIN;
  while (x != cell_nil)
    {
      assert_number ("less_p", CAR (x));
      if (VALUE (car (x)) <= n)
        return cell_f;
      n = VALUE (car (x));
      x = cdr (x);
    }
  return cell_t;
}

SCM
is_p (SCM x) ///((name . "=") (arity . n))
{
  if (x == cell_nil)
    return cell_t;
  assert_number ("is_p", CAR (x));
  int n = VALUE (CAR (x));
  x = cdr (x);
  while (x != cell_nil)
    {
      if (VALUE (car (x)) != n)
        return cell_f;
      x = cdr (x);
    }
  return cell_t;
}

SCM
minus (SCM x) ///((name . "-") (arity . n))
{
  assert_number ("minus", CAR (x));
  SCM a = CAR (x);
  int n = VALUE (a);
  x = cdr (x);
  if (x == cell_nil)
    n = -n;
  while (x != cell_nil)
    {
      assert_number ("minus", CAR (x));
      n -= VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
plus (SCM x) ///((name . "+") (arity . n))
{
  int n = 0;
  while (x != cell_nil)
    {
      assert_number ("plus", CAR (x));
      n += VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
divide (SCM x) ///((name . "/") (arity . n))
{
  int n = 1;
  if (x != cell_nil)
    {
      assert_number ("divide", CAR (x));
      n = VALUE (car (x));
      x = cdr (x);
    }
  while (x != cell_nil)
    {
      assert_number ("divide", CAR (x));
      n /= VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
modulo (SCM a, SCM b)
{
  assert_number ("modulo", a);
  assert_number ("modulo", b);
  int x = VALUE (a);
  while (x < 0) x += VALUE (b);
  return MAKE_NUMBER (x % VALUE (b));
}

SCM
multiply (SCM x) ///((name . "*") (arity . n))
{
  int n = 1;
  while (x != cell_nil)
    {
      assert_number ("multiply", CAR (x));
      n *= VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
logand (SCM x) ///((arity . n))
{
  int n = 0;
  while (x != cell_nil)
    {
      assert_number ("multiply", CAR (x));
      n &= VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
logior (SCM x) ///((arity . n))
{
  int n = 0;
  while (x != cell_nil)
    {
      assert_number ("logior", CAR (x));
      n |= VALUE (car (x));
      x = cdr (x);
    }
  return MAKE_NUMBER (n);
}

SCM
lognot (SCM x)
{
  assert_number ("lognot", x);
  int n = ~VALUE (x);
  return MAKE_NUMBER (n);
}

SCM
ash (SCM n, SCM count)
{
  assert_number ("ash", n);
  assert_number ("ash", count);
  int cn = VALUE (n);
  int ccount = VALUE (count);
  return MAKE_NUMBER ((ccount < 0) ? cn >> -ccount : cn << ccount);
}