/***********************************************************************************[SolverTypes.h]
MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson

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**************************************************************************************************/


#ifndef SolverTypes_h
#define SolverTypes_h

#include <cassert>
#include <stdint.h>

//=================================================================================================
// Variables, literals, lifted booleans, clauses:


// NOTE! Variables are just integers. No abstraction here. They should be chosen from 0..N,
// so that they can be used as array indices.
namespace minisat2 {

typedef int Var;
#define var_Undef (-1)


class Lit
{
		int     x;
	public:
		Lit() : x ( 2*var_Undef )                                              { }   // (lit_Undef)
		explicit Lit ( Var var, bool sign = false ) : x ( ( var+var ) + ( int ) sign ) { }

		// Don't use these for constructing/deconstructing literals. Use the normal constructors instead.
		friend int  toInt ( Lit p );      // Guarantees small, positive integers suitable for array indexing.
		friend Lit  toLit ( int i );      // Inverse of 'toInt()'
		friend Lit  operator   ~ ( Lit p );
		friend bool sign ( Lit p );
		friend int  var ( Lit p );
		friend Lit  unsign ( Lit p );
		friend Lit  id ( Lit p, bool sgn );

		bool operator == ( Lit p ) const { return x == p.x; }
		bool operator != ( Lit p ) const { return x != p.x; }
		bool operator < ( Lit p ) const { return x < p.x;  } // '<' guarantees that p, ~p are adjacent in the ordering.
};

inline  int  toInt ( Lit p )           { return p.x; }
inline  Lit  toLit ( int i )           { Lit p; p.x = i; return p; }
inline  Lit  operator   ~ ( Lit p )           { Lit q; q.x = p.x ^ 1; return q; }
inline  bool sign ( Lit p )           { return p.x & 1; }
inline  int  var ( Lit p )           { return p.x >> 1; }
inline  Lit  unsign ( Lit p )           { Lit q; q.x = p.x & ~1; return q; }
inline  Lit  id ( Lit p, bool sgn ) { Lit q; q.x = p.x ^ ( int ) sgn; return q; }

const Lit lit_Undef ( var_Undef, false );  // }- Useful special constants.
const Lit lit_Error ( var_Undef, true );  // }


//=================================================================================================
// Lifted booleans:


class lbool
{
		char     value;
		explicit lbool ( int v ) : value ( v ) { }

	public:
		lbool()       : value ( 0 ) { }
		lbool ( bool x ) : value ( ( int ) x*2-1 ) { }
		int toInt ( void ) const { return value; }

		bool  operator == ( lbool b ) const { return value == b.value; }
		bool  operator != ( lbool b ) const { return value != b.value; }
		lbool operator ^ ( bool b ) const { return b ? lbool ( -value ) : lbool ( value ); }

		friend int   toInt ( lbool l );
		friend lbool toLbool ( int   v );
};
inline int   toInt ( lbool l ) { return l.toInt(); }
inline lbool toLbool ( int   v ) { return lbool ( v );  }

const lbool l_True  = toLbool ( 1 );
const lbool l_False = toLbool ( -1 );
const lbool l_Undef = toLbool ( 0 );

//=================================================================================================
// Clause -- a simple class for representing a clause:


class Clause
{
		uint32_t size_etc;
		union { float act; uint32_t abst; } extra;
		Lit     data[0];

	public:
		void calcAbstraction()
		{
			uint32_t abstraction = 0;
			for ( int i = 0; i < size(); i++ )
				abstraction |= 1 << ( var ( data[i] ) & 31 );
			extra.abst = abstraction;
		}

		// NOTE: This constructor cannot be used directly (doesn't allocate enough memory).
		template<class V>
		Clause ( const V& ps, bool learnt )
		{
			size_etc = ( ps.size() << 3 ) | ( uint32_t ) learnt;
			for ( int i = 0; i < ps.size(); i++ ) data[i] = ps[i];
			if ( learnt ) extra.act = 0; else calcAbstraction();
		}

		// -- use this function instead:
		template<class V>
		friend Clause* Clause_new ( const V& ps, bool learnt = false )
		{
			assert ( sizeof ( Lit )      == sizeof ( uint32_t ) );
			assert ( sizeof ( float )    == sizeof ( uint32_t ) );
			void* mem = malloc ( sizeof ( Clause ) + sizeof ( uint32_t ) * ( ps.size() ) );
			return new ( mem ) Clause ( ps, learnt );
		}

		int          size ()      const   { return size_etc >> 3; }
		void         shrink ( int i )         { assert ( i <= size() ); size_etc = ( ( ( size_etc >> 3 ) - i ) << 3 ) | ( size_etc & 7 ); }
		void         pop ()              { shrink ( 1 ); }
		bool         learnt ()      const   { return size_etc & 1; }
		uint32_t     mark ()      const   { return ( size_etc >> 1 ) & 3; }
		void         mark ( uint32_t m )    { size_etc = ( size_etc & ~6 ) | ( ( m & 3 ) << 1 ); }
		const Lit&   last ()      const   { return data[size()-1]; }

		// NOTE: somewhat unsafe to change the clause in-place! Must manually call 'calcAbstraction' afterwards for
		//       subsumption operations to behave correctly.
		Lit&         operator [] ( int i )         { return data[i]; }
		Lit          operator [] ( int i ) const   { return data[i]; }
		operator const Lit* ( void ) const         { return data; }

		float&       activity ()              { return extra.act; }
		uint32_t     abstraction () const { return extra.abst; }

		Lit          subsumes ( const Clause& other ) const;
		void         strengthen ( Lit p );
};


/*_________________________________________________________________________________________________
|
|  subsumes : (other : const Clause&)  ->  Lit
|
|  Description:
|       Checks if clause subsumes 'other', and at the same time, if it can be used to simplify 'other'
|       by subsumption resolution.
|
|    Result:
|       lit_Error  - No subsumption or simplification
|       lit_Undef  - Clause subsumes 'other'
|       p          - The literal p can be deleted from 'other'
|________________________________________________________________________________________________@*/
inline Lit Clause::subsumes ( const Clause& other ) const
{
	if ( other.size() < size() || ( extra.abst & ~other.extra.abst ) != 0 )
		return lit_Error;

	Lit        ret = lit_Undef;
	const Lit* c  = ( const Lit* ) ( *this );
	const Lit* d  = ( const Lit* ) other;

	for ( int i = 0; i < size(); i++ )
	{
		// search for c[i] or ~c[i]
		for ( int j = 0; j < other.size(); j++ )
			if ( c[i] == d[j] )
				goto ok;
			else if ( ret == lit_Undef && c[i] == ~d[j] )
			{
				ret = c[i];
				goto ok;
			}

		// did not find it
		return lit_Error;
	ok:;
	}

	return ret;
}


inline void Clause::strengthen ( Lit p )
{
	remove ( *this, p );
	calcAbstraction();
}
}
#endif
