static-if.hh

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#pragma once

#include <utility>

#include <vcsn/misc/type_traits.hh>

namespace vcsn
{
  namespace detail
  {
    template <typename Then, typename Else>
    auto static_if(std::true_type, Then&& then, Else&&)
    {
      return std::forward<Then>(then);
    }

    template <typename Then, typename Else>
    auto static_if(std::false_type, Then&&, Else&& else_)
    {
      return std::forward<Else>(else_);
    }

    template <bool cond, typename Then, typename Else>
    auto static_if(Then&& then, Else&& else_)
    {
      return static_if(bool_constant<cond>{},
                       std::forward<Then>(then),
                       std::forward<Else>(else_));
    }

    template <bool cond, typename Then>
    auto static_if(Then&& then)
    {
      return static_if<cond>(std::forward<Then>(then),
                             [](auto&&...){});
    }
  }
}