///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com

Copyright(c) 2018 jwellbelove

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
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******************************************************************************/

#ifndef ETL_PERMUTATIONS_INCLUDED
#define ETL_PERMUTATIONS_INCLUDED

#include "platform.h"

///\defgroup permutations permutations
/// permutations<N, K> : Calculates K permutations from N.
///\ingroup maths

namespace etl 
{
  //***************************************************************************
  ///\ingroup permutations
  /// Calculates permutaions.
  //***************************************************************************
  template <const size_t NV, const size_t KV>
  struct permutations
  {
    static ETL_CONSTANT size_t value = NV * permutations<NV - 1, KV - 1>::value;
  };

  //***************************************************************************
  /// Calculates permutations.
  /// Specialisation for KV == 0.
  //***************************************************************************
  template <const size_t NV>
  struct permutations<NV, 0>
  {
    static ETL_CONSTANT size_t value = 1;
  };

#if ETL_CPP17_SUPPORTED
  template <size_t NV, size_t KV>
  inline constexpr size_t permutations_v = permutations<NV, KV>::value;
#endif
}

#endif
