///\file

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

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

Copyright(c) 2018 John Wellbelove

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
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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The above copyright notice and this permission notice shall be included in all
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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******************************************************************************/

#ifndef ETL_COMBINATIONS_INCLUDED
#define ETL_COMBINATIONS_INCLUDED

#include "platform.h"
#include "permutations.h"
#include "factorial.h"

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

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

  template <size_t NV, size_t KV>
  ETL_CONSTANT size_t combinations<NV, KV>::value;

#if ETL_USING_CPP17
  template <size_t NV, size_t KV>
  inline constexpr size_t combinations_v = combinations<NV, KV>::value;
#endif
}

#endif