osprey/be/lno/frac.h

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/*

  Copyright (C) 2000, 2001 Silicon Graphics, Inc.  All Rights Reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of version 2 of the GNU General Public License as
  published by the Free Software Foundation.

  This program is distributed in the hope that it would be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

  Further, this software is distributed without any warranty that it is
  free of the rightful claim of any third person regarding infringement 
  or the like.  Any license provided herein, whether implied or 
  otherwise, applies only to this software file.  Patent licenses, if 
  any, provided herein do not apply to combinations of this program with 
  other software, or any other product whatsoever.  

  You should have received a copy of the GNU General Public License along
  with this program; if not, write the Free Software Foundation, Inc., 59
  Temple Place - Suite 330, Boston MA 02111-1307, USA.

  Contact information:  Silicon Graphics, Inc., 1600 Amphitheatre Pky,
  Mountain View, CA 94043, or:

  http://www.sgi.com

  For further information regarding this notice, see:

  http://oss.sgi.com/projects/GenInfo/NoticeExplan

*/


// -*-C++-*-

#ifndef frac_INCLUDED
#define frac_INCLUDED

extern "C" {
#ifndef defs_INCLUDED
#include "defs.h"
#endif
#ifndef ERRORS_INCLUDED
#include "errors.h"
#endif
}

// note that 16/32 bit implementations are equally possible, possibly faster,
// definitely untested.  Could have a template for this, but let's keep away
// from those where possible.  Actually, could have a macro as well, but this
// will be good enough.

#define FRAC_ETY  mINT32    /* element type */
#define FRAC_ITY  mINT64    /* intermediate result type, bigger */

#ifdef Is_True_On
/* better to have a smaller number when testing, to point out problems */
#define FRAC_MAX  1000000
#else
/* better to have a larger number in production -- safer. */
#define FRAC_MAX  INT32_MAX
#endif

class FRAC {
 public:
  static BOOL Exception;

  FRAC() {_n = 0; _d = 1;}
  FRAC(FRAC_ETY n) : _n(_checksz(n)), _d(1) {}
  FRAC(FRAC_ETY n, FRAC_ETY d) : _n(n), _d(d) {_reduce();}
  FRAC(const FRAC& f) : _n(f._n), _d(f._d) {}
  // ~FRAC() {} /* forces a slower vector deallocator -- very bad */

  FRAC_ETY N() const {return _n;}
  FRAC_ETY D() const {return _d;}

  FRAC& operator =(const FRAC& f) {_n = f._n; _d = f._d; return *this;}

  BOOL    operator ==(FRAC f) const
    {return _n == f._n && _d == f._d;}
  BOOL    operator !=(FRAC f) const
    {return _n != f._n || _d != f._d;}
  BOOL    operator <(FRAC f) const
    {return FRAC_ITY(_n)*f._d < FRAC_ITY(f._n)*_d;}
  BOOL    operator <=(FRAC f) const
    {return FRAC_ITY(_n)*f._d <= FRAC_ITY(f._n)*_d;}
  BOOL    operator >(FRAC f) const
    {return FRAC_ITY(_n)*f._d > FRAC_ITY(f._n)*_d;}
  BOOL    operator >=(FRAC f) const
    {return FRAC_ITY(_n)*f._d >= FRAC_ITY(f._n)*_d;}

  FRAC_ETY  Integer() const
    {FmtAssert(_d == 1, ("int(%d/%d)", _n, _d)); return _n;}
  double  Real() const
    {return (double(_n))/_d;}

  FRAC    operator +(FRAC f) const;
  FRAC&   operator +=(FRAC f) {return (*this) = (*this) + f;}
  FRAC    operator -(FRAC f) const;
  FRAC&   operator -=(FRAC f) {return (*this) = (*this) - f;}
  FRAC    operator *(FRAC f) const;
  FRAC&   operator *=(FRAC f) {return (*this) = (*this) * f;}
  FRAC    operator /(FRAC f) const;
  FRAC&   operator /=(FRAC f) {return (*this) = (*this) / f;}
  FRAC    operator -() const {return FRAC(-_n, _d, 0);}

  FRAC    Abs() const {return FRAC(_n < 0 ? -_n : _n, _d, 0);}
  friend FRAC Abs(FRAC f) {return f.Abs();}

  void    Print(FILE* f) const;
  char*   Print(char* f) const;

 private:

  FRAC(FRAC_ITY n, FRAC_ITY d) {_reduce(n, d);}
  FRAC(FRAC_ETY n, FRAC_ETY d, INT32) : _n(n), _d(d) {} // if don't need reduce

  // entry point for reducing fractions
  // probably too much inlining, but much will be constant folded away

  void _reduce() {
    if (_d == 1)
      _n = _checksz(_n);
    else if (_n == 0) {
      _d = 1;
    }
    else if (_n == 1 || _n == -1) {
      _n = _d < 0 ? -_n : _n;
      _d = _checksz(_d < 0 ? -_d : _d);
    }
    else if (_d == -1) {
      _n = _checksz(-_n);
      _d = -_d;
    }
    else
      _reduce2();
  }

  // entry point for reducing intermediate expressions
  void _reduce(FRAC_ITY n, FRAC_ITY d) {
    if (d == 1) {
      _n = _checksz(n);
      _d = 1;
    }
    else if (n == 0) {
      _n = 0;
      _d = 1;
    }
    else if (n == 1 || n == -1) {
      _n = d < 0 ? FRAC_ETY(-n) : FRAC_ETY(n);
      _d = _checksz(d < 0 ? -d : d);
    }
    else if (d == -1) {
      _n = _checksz(-n);
      _d = 1;
    }
    else
      _reduce2(n, d);
  }

  // general reduce, for when _d and _n are not -1, 0, 1.
  // called by _reduce() only

  void _reduce2();
  void _reduce2(FRAC_ITY n, FRAC_ITY d);

  // use these to warn if fractions aren't doing well, and doing
  // the best thing possible from there
  static FRAC_ETY _checksz(FRAC_ETY x) {
    if (!_sz_ok(x)) {
      if (Exception == FALSE) {
        DevWarn("FRAC component too big: %d", x);
        Exception = TRUE;
      }
      x = MIN(x, FRAC_MAX);
      x = MAX(x, -FRAC_MAX);
    }
    return x;
  }
  static FRAC_ETY _checksz(FRAC_ITY x) {
    if (!_sz_ok(x)) {
      if (Exception == FALSE) {
        DevWarn("FRAC component too big: %lld", x);
        Exception = TRUE;
      }
      x = MIN(x, FRAC_MAX);
      x = MAX(x, -FRAC_MAX);
    }
    return FRAC_ETY(x);
  }
  static FRAC _checksz(FRAC_ETY n, FRAC_ETY d) {
    FRAC   f;
    if (!_sz_ok(n) || !_sz_ok(d)) {
      if (Exception == FALSE) {
        DevWarn("FRAC component too big: %d/%d", n, d);
        Exception = TRUE;
      }
      f._n = d == 0 ? 1 : n/d;
      f._d = 1;
    }
    else {
      f._n = n;
      f._d = d;
    }
    return f;
  }
  static FRAC _checksz(FRAC_ITY n, FRAC_ITY d) {
    FRAC   f;
    if (!_sz_ok(n) || !_sz_ok(d)) {
      if (Exception == FALSE) {
        DevWarn("FRAC component too big: %lld/%lld", n, d);
        Exception = TRUE;
      }
      f._n = d == 0 ? 1 : n/d;
      f._d = 1;
    }
    else {
      f._n = n;
      f._d = d;
    }
    return f;
  }

  // _sz_ok: return whether components are too big
  static BOOL _sz_ok(FRAC_ITY x) {
    return (x <= FRAC_MAX && x >= -FRAC_MAX);
  }
  static BOOL _sz_ok(FRAC_ITY n, FRAC_ITY d) {
    return _sz_ok(n) && _sz_ok(d);
  }
  static BOOL _sz_ok(FRAC_ETY x) {
    return (x <= FRAC_MAX && x >= -FRAC_MAX);
  }
  static BOOL _sz_ok(FRAC_ETY n, FRAC_ETY d) {
    return _sz_ok(n) && _sz_ok(d);
  }

  FRAC_ETY  _n; // any integral value
  FRAC_ETY  _d; // must be positive.  signed so FRAC_ITY easy
};
#endif

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