include/ruby/3/arithmetic/fixnum.h

   1 /**                                                     \noop-*-C++-*-vi:ft=cpp
   2  * @file
   3  * @author     Ruby developers <ruby-core@ruby-lang.org>
   4  * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
   5  *             Permission  is hereby  granted,  to  either redistribute  and/or
   6  *             modify this file, provided that  the conditions mentioned in the
   7  *             file COPYING are met.  Consult the file for details.
   8  * @warning    Symbols   prefixed   with   either  `RUBY3`   or   `ruby3`   are
   9  *             implementation details.   Don't take  them as canon.  They could
  10  *             rapidly appear then vanish.  The name (path) of this header file
  11  *             is also an  implementation detail.  Do not expect  it to persist
  12  *             at the place it is now.  Developers are free to move it anywhere
  13  *             anytime at will.
  14  * @note       To  ruby-core:  remember  that   this  header  can  be  possibly
  15  *             recursively included  from extension  libraries written  in C++.
  16  *             Do not  expect for  instance `__VA_ARGS__` is  always available.
  17  *             We assume C99  for ruby itself but we don't  assume languages of
  18  *             extension libraries. They could be written in C++98.
  19  * @brief      Handling of integers formerly known as Fixnums.
  20  */
  21 #ifndef  RUBY3_ARITHMETIC_FIXNUM_H
  22 #define  RUBY3_ARITHMETIC_FIXNUM_H
  23 #include "ruby/backward/2/limits.h"
  24
  25 #define FIXABLE    RB_FIXABLE
  26 #define FIXNUM_MAX RUBY_FIXNUM_MAX
  27 #define FIXNUM_MIN RUBY_FIXNUM_MIN
  28 #define NEGFIXABLE RB_NEGFIXABLE
  29 #define POSFIXABLE RB_POSFIXABLE
  30
  31 /*
  32  * FIXABLE can be applied to anything, from double to intmax_t.  The problem is
  33  * double.   On a  64bit system  RUBY_FIXNUM_MAX is  4,611,686,018,427,387,903,
  34  * which is not representable by a double.  The nearest value that a double can
  35  * represent  is   4,611,686,018,427,387,904,  which   is  not   fixable.   The
  36  * seemingly-stragne "< FIXNUM_MAX + 1" expression below is due to this.
  37  */
  38 #define RB_POSFIXABLE(_) ((_) <  RUBY_FIXNUM_MAX + 1)
  39 #define RB_NEGFIXABLE(_) ((_) >= RUBY_FIXNUM_MIN)
  40 #define RB_FIXABLE(_)    (RB_POSFIXABLE(_) && RB_NEGFIXABLE(_))
  41 #define RUBY_FIXNUM_MAX  (LONG_MAX / 2)
  42 #define RUBY_FIXNUM_MIN  (LONG_MIN / 2)
  43
  44 #endif /* RUBY3_ARITHMETIC_FIXNUM_H */