Utilities.h

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#ifndef Analysis_Tools_Utilities_h
#define Analysis_Tools_Utilities_h

// Original code: CMSSW_10_2_22 - CondFormats/JetMETObjects/interface/Utilities.h

#include <stdexcept>
#include <cstdlib>
#include <sstream>
#include <string>
#include <vector>
#include <tuple>
#include <cmath>
#include <utility>

namespace std
{
  //These functions print a tuple using a provided std::ostream
  template<typename Type, unsigned N, unsigned Last>
  struct tuple_printer {
  
      static void print(std::ostream& out, const Type& value) {
          out << std::get<N>(value) << ", ";
          tuple_printer<Type, N + 1, Last>::print(out, value);
      }
  };
  template<typename Type, unsigned N>
  struct tuple_printer<Type, N, N> {
  
      static void print(std::ostream& out, const Type& value) {
          out << std::get<N>(value);
      }
  
  };
  template<typename... Types>
  std::ostream& operator<<(std::ostream& out, const std::tuple<Types...>& value) {
      out << "(";
      tuple_printer<std::tuple<Types...>, 0, sizeof...(Types) - 1>::print(out, value);
      out << ")";
      return out;
  }
  //----------------------------------------------------------------------
  //Returns a list of type indices
  template <size_t... n>
  struct ct_integers_list {
      template <size_t m>
      struct push_back
      {
          typedef ct_integers_list<n..., m> type;
      };
  };
  template <size_t max>
  struct ct_iota_1
  {
      typedef typename ct_iota_1<max-1>::type::template push_back<max>::type type;
  };
  template <>
  struct ct_iota_1<0>
  {
      typedef ct_integers_list<> type;
  };
  //----------------------------------------------------------------------
  //Return a tuple which is a subset of the original tuple
  //This function pops an entry off the font of the tuple
  template <size_t... indices, typename Tuple>
  auto tuple_subset(const Tuple& tpl, ct_integers_list<indices...>)
      -> decltype(std::make_tuple(std::get<indices>(tpl)...))
  {
      return std::make_tuple(std::get<indices>(tpl)...);
      // this means:
      //   make_tuple(get<indices[0]>(tpl), get<indices[1]>(tpl), ...)
  }
  template <typename Head, typename... Tail>
  std::tuple<Tail...> tuple_tail(const std::tuple<Head, Tail...>& tpl)
  {
      return tuple_subset(tpl, typename ct_iota_1<sizeof...(Tail)>::type());
      // this means:
      //   tuple_subset<1, 2, 3, ..., sizeof...(Tail)-1>(tpl, ..)
  }
  //----------------------------------------------------------------------
  //Recursive hashing function for tuples
  template<typename Head, typename... ndims> struct hash_specialization
  {
    typedef std::tuple<Head,ndims...> argument_type;
    typedef std::size_t result_type;
    result_type operator()(const argument_type& t) const
    {
      const uint32_t& b = reinterpret_cast<const uint32_t&>(std::get<0>(t));
      //const uint32_t& more = (*this)(tuple_tail(t));
      const uint32_t& more = hash_specialization<ndims...>()(tuple_tail(t));
      return b^more;
    }
  };
  //Base case
  template<> struct hash_specialization<float>
  {
    typedef std::tuple<float> argument_type;
    typedef std::size_t result_type;
    result_type operator()(const argument_type& t) const
    {
      const uint32_t& b = reinterpret_cast<const uint32_t&>(std::get<0>(t));
      return static_cast<result_type>(b);
    } 
  };
  //Overloaded verions of std::hash for tuples
  template<typename Head, typename... ndims> struct hash<std::tuple<Head, ndims...> >
  {
    typedef std::tuple<Head,ndims...> argument_type;
    typedef std::size_t result_type;
    result_type operator()(const argument_type& t) const
    {
      return hash_specialization<Head,ndims...>()(t);
    }
  };
  template<> struct hash<std::tuple<> >
  {
    typedef std::tuple<> argument_type;
    typedef std::size_t result_type;
    result_type operator()(const argument_type& t) const
    {
      return -1;
    }  
  };
}

namespace
{
  void handleError(const std::string& fClass, const std::string& fMessage)
  {
    std::stringstream sserr;
    sserr<<fClass<<" ERROR: "<<fMessage;
    throw std::runtime_error(sserr.str());
  }
  //----------------------------------------------------------------------
  inline float getFloat(const std::string& token)
  {
    char* endptr;
    float result = strtod (token.c_str(), &endptr);
    if (endptr == token.c_str())
      {
        std::stringstream sserr;
        sserr<<"can't convert token "<<token<<" to float value";
    handleError("getFloat",sserr.str());
      }
    return result;
  }
  //----------------------------------------------------------------------
  inline unsigned getUnsigned(const std::string& token)
  {
    char* endptr;
    unsigned result = strtoul (token.c_str(), &endptr, 0);
    if (endptr == token.c_str())
      {
        std::stringstream sserr;
        sserr<<"can't convert token "<<token<<" to unsigned value";
    handleError("getUnsigned",sserr.str());
      }
    return result;
  }
  inline long int getSigned(const std::string& token)
  {
    char* endptr;
    unsigned result = strtol (token.c_str(), &endptr, 0);
    if (endptr == token.c_str())
      {
        std::stringstream sserr;
        sserr<<"can't convert token "<<token<<" to signed value";
    handleError("getSigned",sserr.str());
      }
    return result;
  }
  //----------------------------------------------------------------------
  inline std::string getSection(const std::string& token)
  {
    size_t iFirst = token.find ('[');
    size_t iLast = token.find (']');
    if (iFirst != std::string::npos && iLast != std::string::npos && iFirst < iLast)
      return std::string (token, iFirst+1, iLast-iFirst-1);
    return "";
  }
  //----------------------------------------------------------------------
  inline std::vector<std::string> getTokens(const std::string& fLine)
  {
    std::vector<std::string> tokens;
    std::string currentToken;
    for (unsigned ipos = 0; ipos < fLine.length (); ++ipos)
      {
        char c = fLine[ipos];
        if (c == '#') break; // ignore comments
        else if (c == ' ')
          { // flush current token if any
            if (!currentToken.empty())
              {
            tokens.push_back(currentToken);
            currentToken.clear();
              }
          }
        else
          currentToken += c;
      }
    if (!currentToken.empty()) tokens.push_back(currentToken); // flush end
    return tokens;
  }
  //----------------------------------------------------------------------
  inline std::string getDefinitions(const std::string& token)
  {
    size_t iFirst = token.find ('{');
    size_t iLast = token.find ('}');
    if (iFirst != std::string::npos && iLast != std::string::npos && iFirst < iLast)
      return std::string (token, iFirst+1, iLast-iFirst-1);
    return "";
  }
  //------------------------------------------------------------------------
  inline float quadraticInterpolation(float fZ, const float fX[3], const float fY[3])
  {
    // Quadratic interpolation through the points (x[i],y[i]). First find the parabola that
    // is defined by the points and then calculate the y(z).
    float D[4],a[3];
    D[0] = fX[0]*fX[1]*(fX[0]-fX[1])+fX[1]*fX[2]*(fX[1]-fX[2])+fX[2]*fX[0]*(fX[2]-fX[0]);
    D[3] = fY[0]*(fX[1]-fX[2])+fY[1]*(fX[2]-fX[0])+fY[2]*(fX[0]-fX[1]);
    D[2] = fY[0]*(pow(fX[2],2)-pow(fX[1],2))+fY[1]*(pow(fX[0],2)-pow(fX[2],2))+fY[2]*(pow(fX[1],2)-pow(fX[0],2));
    D[1] = fY[0]*fX[1]*fX[2]*(fX[1]-fX[2])+fY[1]*fX[0]*fX[2]*(fX[2]-fX[0])+fY[2]*fX[0]*fX[1]*(fX[0]-fX[1]);
    if (D[0] != 0)
      {
        a[0] = D[1]/D[0];
        a[1] = D[2]/D[0];
        a[2] = D[3]/D[0];
      }
    else
      {
        a[0] = 0.0;
        a[1] = 0.0;
        a[2] = 0.0;
      }
    float r = a[0]+fZ*(a[1]+fZ*a[2]);
    return r;
  }
  //------------------------------------------------------------------------
  //Generates a std::tuple type based on a stored type and the number of
  // objects in the tuple.
  //Note: All of the objects will be of the same type
  template<typename /*LEFT_TUPLE*/, typename /*RIGHT_TUPLE*/>
  struct join_tuples
  {
  };
  template<typename... LEFT, typename... RIGHT>
  struct join_tuples<std::tuple<LEFT...>, std::tuple<RIGHT...>>
  {
    typedef std::tuple<LEFT..., RIGHT...> type;
  };
  template<typename T, unsigned N>
  struct generate_tuple_type
  {
    typedef typename generate_tuple_type<T, N/2>::type left;
    typedef typename generate_tuple_type<T, N/2 + N%2>::type right;
    typedef typename join_tuples<left, right>::type type;
  };
  template<typename T>
  struct generate_tuple_type<T, 1>
  {
    typedef std::tuple<T> type;
  };
  template<typename T>
  struct generate_tuple_type<T, 0>
  {
    typedef std::tuple<> type;
  };
  //------------------------------------------------------------------------
  //C++11 implementation of make_index_sequence, which is a C++14 function
  // using aliases for cleaner syntax
  template<class T> using Invoke = typename T::type;

  template<unsigned...> struct seq{ using type = seq; };

  template<class S1, class S2> struct concat;

  template<unsigned... I1, unsigned... I2>
  struct concat<seq<I1...>, seq<I2...>>
    : seq<I1..., (sizeof...(I1)+I2)...>{};

  template<class S1, class S2>
  using Concat = Invoke<concat<S1, S2>>;

  template<unsigned N> struct gen_seq;
  template<unsigned N> using GenSeq = Invoke<gen_seq<N>>;

  template<unsigned N>
  struct gen_seq : Concat<GenSeq<N/2>, GenSeq<N - N/2>>{};

  template<> struct gen_seq<0> : seq<>{};
  template<> struct gen_seq<1> : seq<0>{};
  //------------------------------------------------------------------------
  //Generates a tuple based on a given function (i.e. lambda expression)
  template <typename F, unsigned... Is>
  auto gen_tuple_impl(F func, seq<Is...> )
    -> decltype(std::make_tuple(func(Is)...))
  {
      return std::make_tuple(func(Is)...);
  }
  template <unsigned N, typename F>
  auto gen_tuple(F func) 
    -> decltype(gen_tuple_impl(func, GenSeq<N>() ))
  {
      return gen_tuple_impl(func, GenSeq<N>() );
  }
}
#endif