73ef4ff3
 Hu Chunming
提交三方库
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/*=============================================================================
Copyright (c) 2017 Paul Fultz II
in.cpp
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
/*=============================================================================
Copyright (c) 2016 Paul Fultz II
in.cpp
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#include "example.h"
using namespace boost::hof;
#ifdef _MSC_VER
template<class R, class T>
auto member_find(const R& r, const T& x) BOOST_HOF_RETURNS(r.find(x));
#endif
// Function to find an iterator using a containers built-in find if available
BOOST_HOF_STATIC_LAMBDA_FUNCTION(find_iterator) = first_of(
[](const std::string& s, const auto& x)
{
auto index = s.find(x);
if (index == std::string::npos) return s.end();
else return s.begin() + index;
},
#ifdef _MSC_VER
// On MSVC, trailing decltype doesn't work with generic lambdas, so a
// seperate function can be used instead.
BOOST_HOF_LIFT(member_find),
#else
[](const auto& r, const auto& x) BOOST_HOF_RETURNS(r.find(x)),
#endif
[](const auto& r, const auto& x)
{
using std::begin;
using std::end;
return std::find(begin(r), end(r), x);
}
);
// Implement an infix `in` operator to check if a range contains an element
BOOST_HOF_STATIC_LAMBDA_FUNCTION(in) = infix(
[](const auto& x, const auto& r)
{
using std::end;
return find_iterator(r, x) != end(r);
}
);
// Negate version of `in`
BOOST_HOF_STATIC_LAMBDA_FUNCTION(not_in) = infix(compose(not _, in));
int main()
{
// Check if vector contains element
std::vector<int> numbers = { 1, 2, 3, 4, 5 };
if (5 <in> numbers) std::cout << "Yes" << std::endl;
// Check if string contains element
std::string s = "hello world";
if ("hello" <in> s) std::cout << "Yes" << std::endl;
// Check if map contains element
std::map<int, std::string> number_map = {
{ 1, "1" },
{ 2, "2" },
{ 3, "3" },
{ 4, "4" }
};
if (4 <in> number_map) std::cout << "Yes" << std::endl;
// Check if map doesn't contains element
if (not (8 <in> numbers)) std::cout << "No" << std::endl;
if (8 <not_in> numbers) std::cout << "No" << std::endl;
}
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