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// file : butl/utility -*- C++ -*-
// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUTL_UTILITY
#define BUTL_UTILITY
#include <cstddef> // std::size_t
#include <utility> // forward()
#include <cstring> // strcmp
namespace butl
{
// Key comparators (i.e., to be used in sets, maps, etc).
//
struct compare_c_string
{
bool operator() (const char* x, const char* y) const
{
return std::strcmp (x, y) < 0;
}
};
struct compare_pointer_target
{
template <typename P>
bool operator() (const P& x, const P& y) const {return *x < *y;}
};
// Combine one or more hash values.
//
inline std::size_t
combine_hash (std::size_t s, std::size_t h)
{
// Magic formula from boost::hash_combine().
//
return s ^ (h + 0x9e3779b9 + (s << 6) + (s >> 2));
}
template <typename... S>
inline std::size_t
combine_hash (std::size_t s, std::size_t h, S... hs)
{
return combine_hash (combine_hash (s, h), hs...);
}
// Support for reverse iteration using range-based for-loop:
//
// for (... : reverse_iterate (x)) ...
//
template <typename T>
class reverse_range
{
T x_;
public:
reverse_range (T&& x): x_ (std::forward<T> (x)) {}
auto begin () const -> decltype (this->x_.rbegin ()) {return x_.rbegin ();}
auto end () const -> decltype (this->x_.rend ()) {return x_.rend ();}
};
template <typename T>
inline reverse_range<T>
reverse_iterate (T&& x) {return reverse_range<T> (std::forward<T> (x));}
}
#endif // BUTL_UTILITY
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