Semirings.h

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#ifndef _SEMIRINGS_H_
#define _SEMIRINGS_H_
 
#include <utility>
#include <climits>
#include <cmath>
#include "promote.h"
 
template <typename T>
struct inf_plus{
  T operator()(const T& a, const T& b) const {
    T inf = std::numeric_limits<T>::max();
        if (a == inf || b == inf){
            return inf;
        }
        return a + b;
  }
};
 
 
template <class T1, class T2>
struct PlusTimesSRing
{
    typedef typename promote_trait<T1,T2>::T_promote T_promote;
 
    static T_promote add(const T1 & arg1, const T2 & arg2)
    {
        return (static_cast<T_promote>(arg1) +  
            static_cast<T_promote>(arg2) );
    }
    static T_promote multiply(const T1 & arg1, const T2 & arg2)
    {
        return (static_cast<T_promote>(arg1) * 
            static_cast<T_promote>(arg2) );
 
    }
};
 
 
template <class T1, class T2>
struct MinPlusSRing
{
    typedef typename promote_trait<T1,T2>::T_promote T_promote;
 
    static T_promote add(const T1 & arg1, const T2 & arg2)
    {
        return std::min<T_promote> 
        (static_cast<T_promote>(arg1), static_cast<T_promote>(arg2));
    }
    static T_promote multiply(const T1 & arg1, const T2 & arg2)
    {
        return inf_plus< T_promote > 
        (static_cast<T_promote>(arg1), static_cast<T_promote>(arg2));
    }
};
 
 
#endif