epsilon-profile.hh

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#pragma once

#include <ostream>
#include <tuple>

namespace vcsn
{
  namespace detail
  {

    template <typename State>
    struct epsilon_profile
    {
      using state_t = State;

      state_t state;
      size_t in_sp;
      size_t in_nsp;
      size_t out_sp;
      size_t out_nsp;

      epsilon_profile(state_t s,
                      size_t insp, size_t in,
                      size_t outsp, size_t out)
        : state(s)
        , in_sp(insp), in_nsp(in - insp)
        , out_sp(outsp), out_nsp(out - outsp)
      {}

      void update(size_t insp, size_t in,
                  size_t outsp, size_t out)
      {
        in_sp = insp;
        in_nsp = in - insp;
        out_sp = outsp;
        out_nsp = out - outsp;
      }

      bool operator<(const epsilon_profile& r) const
      {
        // (i) First, work on those with fewer outgoing spontaneous
        // transitions.
        // (ii) Prefer fewer outgoing transitions.
        // (iii) Prefer fewer incoming spontaneous transitions.
        // (iv) Then, ensure total order using state handle.
        //
        // Note the inversions between lhs and rhs.
        return (std::tie  (r.out_sp, r.out_nsp, r.in_sp, state)
                < std::tie(out_sp,   out_nsp,   in_sp,   r.state));
      }

      friend std::ostream& operator<<(std::ostream& o, const epsilon_profile& p)
      {
        return o << p.state
                 << 'o' << p.out_sp
                 << 'O' << p.out_nsp
                 << 'i' << p.in_sp
                 << 'I' << p.in_nsp;
      }
    };
  }
}