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#pragma once is a widely supported compiler pragma, even though it is not part of the C++ standard. Many of the issues keeping #pragma once from being standardized (distributed filesystems, build farms, hard links, etc.) do not apply to CMake - it is easy to build CMake on a single machine. CMake also does not install any header files which can be consumed by other projects (though cmCPluginAPI.h has been deliberately omitted from this conversion in case anyone is still using it.) Finally, #pragma once has been required to build CMake since at least August 2017 (7f29bbe6enabled server mode unconditionally, which had been using #pragma once since September 2016 (b13d3e0d)). The fact that we now require C++11 filters out old compilers, and it is unlikely that there is a compiler which supports C++11 but does not support #pragma once.
49 lines
1.6 KiB
C++
49 lines
1.6 KiB
C++
// -*-c++-*-
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// vim: set ft=cpp:
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/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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file Copyright.txt or https://cmake.org/licensing for details. */
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#pragma once
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#include <iterator>
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#include <cm/type_traits>
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namespace cm {
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// checks if a type is an iterator type
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template <typename I>
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using is_iterator =
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std::is_integral<typename std::iterator_traits<I>::difference_type>;
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// checks if a type is an input iterator type
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template <typename I>
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using is_input_iterator =
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std::is_base_of<std::input_iterator_tag,
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typename std::iterator_traits<I>::iterator_category>;
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// checks if a type is a range type: std::begin() and std::end() are supported
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template <typename Range>
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using is_range = cm::bool_constant<
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cm::is_iterator<decltype(std::begin(std::declval<const Range>()))>::value &&
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cm::is_iterator<decltype(std::end(std::declval<const Range>()))>::value>;
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// checks if a type is an input range type: std::begin() and std::end() are
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// returning an input iterator
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template <typename Range>
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using is_input_range =
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#if defined(_MSC_VER) && _MSC_VER < 1920
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// MS C++ is not able to evaluate complex type introspection,
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// so use a simplified version
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cm::bool_constant<std::is_class<Range>::value ||
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std::is_pointer<Range>::value ||
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std::is_array<Range>::value>;
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#else
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cm::bool_constant<cm::is_input_iterator<decltype(
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std::begin(std::declval<const Range>()))>::value &&
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cm::is_input_iterator<decltype(
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std::end(std::declval<const Range>()))>::value>;
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#endif
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} // namespace cm
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