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3rdparty/boost_1_81_0/libs/hana/example/fold.cpp 929 Bytes
73ef4ff3   Hu Chunming   提交三方库
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  // Copyright Louis Dionne 2013-2022
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
  
  #include <boost/hana/assert.hpp>
  #include <boost/hana/fold.hpp>
  #include <boost/hana/tuple.hpp>
  
  #include <sstream>
  #include <string>
  namespace hana = boost::hana;
  
  
  auto to_string = [](auto x) {
      std::ostringstream ss;
      ss << x;
      return ss.str();
  };
  
  int main() {
      auto f = [=](std::string s, auto element) {
          return "f(" + s + ", " + to_string(element) + ")";
      };
  
      // with an initial state
      BOOST_HANA_RUNTIME_CHECK(
          hana::fold(hana::make_tuple(2, '3', 4, 5.0), "1", f)
              ==
          "f(f(f(f(1, 2), 3), 4), 5)"
      );
  
      // without initial state
      BOOST_HANA_RUNTIME_CHECK(
          hana::fold(hana::make_tuple("1", 2, '3', 4, 5.0), f)
              ==
          "f(f(f(f(1, 2), 3), 4), 5)"
      );
  }