/usr/include/linbox/switch/boolean.h is in liblinbox-dev 1.1.6~rc0-4.1.
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/* linbox/switch/boolean.h
* Copyright (C) 1999-2001 William J Turner
*
* Written by William J Turner <wjturner@math.ncsu.edu>,
*
* -----------------------------------------------------------
* 2002-09-26 Bradford Hovinen <bghovinen@math.uwaterloo.ca>
*
* Refactoring: The switch object now contains only the information for one 2x2
* block. A vector of switches is maintained by the butterfly preconditioner
* instead of the switch object. Since there will be many switch objects, they
* should be kept very lightweight, so the field is not maintained in the object
* itself, but instead passed to apply and applyTranspose. Since those methods
* are inline, this does not create overhead. apply and applyTranspose now take
* four field elements: the source elements and destination elements. This
* eliminates the need to keep an additional temporary in the class, and
* eliminates the need for copying in the butterfly.
*
* -----------------------------------------------------------
* 2002-08-20 Bradford Hovinen <hovinen@cis.udel.edu>
*
* Brought this file into the current Linbox framework:
* - Renamed file as boolean.h
* - Renamed class boolean_switch as BooleanSwitch
* - Reindent
* -----------------------------------------------------------
*
* See COPYING for license information.
*/
#ifndef __BOOLEAN_H
#define __BOOLEAN_H
#include <vector>
namespace LinBox
{
class BooleanSwitchFactory;
/** Boolean switch object.
* This is a switch predicate object that is applied
* to two references to elements to switch them as needed
* by the \Ref{Butterfly Switching Network BlackBox Matrix Object}.
*/
class BooleanSwitch
{
public:
typedef BooleanSwitchFactory Factory;
/** Constructor from an STL vector of booleans.
* The switch is applied using the vector of booleans.
* A true value means to swap the two elements, and a false
* value means not to.
* The apply function starts at the beginning of the vector moving
* forward through it, and applyTranspose function starts at the end
* moving backwards. Both repeat the vector after they pass through it.
* @param switches vector of switches
*/
BooleanSwitch (const bool s)
: _s (s)
{}
/** Destructor.
*/
~BooleanSwitch () {}
/** Apply switch function.
* Switches the elements in references according to current boolean
* value. Swaps the elements if boolean is true, otherwise does nothing.
* It is templatized by the element type to be swapped.
* @return bool true if swapped, false otherwise
* @param x reference to first element to be switched
* @param y reference to second element to be switched
*/
template <class Field>
bool apply (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const;
/** Apply switch transpose function.
* Switches the elements in references according to current boolean
* value. Swaps the elements if boolean is true, otherwise does nothing.
* It is templatized by the element type to be swapped.
* @return bool true if swapped, false otherwise
* @param x reference to first element to be switched
* @param y reference to second element to be switched
*/
template <class Field>
bool applyTranspose (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const;
private:
bool _s;
}; // class boolean_switch
/** Boolean switch factory
*
* This class facilitates construction of boolean switch objects by the
* butterfly matrix.
*/
class BooleanSwitchFactory
{
public:
/** Constructor from an STL vector of bools
*/
BooleanSwitchFactory (const std::vector<bool> &switches)
: _switches (switches), _iter (switches.begin ())
{}
/** Construct and return a boolean switch object
*
* This function walks through the switches object given in the
* constructor, advancing on each invocation. It wraps around to the
* beginning of the vector when it reaches the end.
*/
BooleanSwitch makeSwitch ()
{
if (_iter == _switches.end ())
_iter = _switches.begin ();
return BooleanSwitch (*_iter++);
}
private:
const std::vector<bool> &_switches;
std::vector<bool>::const_iterator _iter;
};
template <class Field>
inline bool BooleanSwitch::apply (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const
{
if (_s)
std::swap (x, y);
return _s;
}
template <class Field>
inline bool BooleanSwitch::applyTranspose (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const
{
if (_s)
std::swap (x, y);
return _s;
}
}
#endif // __BOOLEAN_H
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