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  1. #define BOOST_SPIRIT_USE_PHOENIX_V3
  2. #include <boost/spirit/include/qi.hpp>
  3. #include <boost/spirit/include/phoenix.hpp>
  4. #include <boost/phoenix/function/adapt_function.hpp>
  5.  
  6. void add_operand(double& lhs, double rhs) { lhs += rhs; }
  7. void sub_operand(double& lhs, double rhs) { lhs -= rhs; }
  8.  
  9. BOOST_PHOENIX_ADAPT_FUNCTION(void, add_, add_operand, 2)
  10. BOOST_PHOENIX_ADAPT_FUNCTION(void, sub_, sub_operand, 2)
  11.  
  12. int main()
  13. {
  14.     const std::string INPUT_DATA = "12e-1 + 3.4 - .67";
  15.     typedef std::string::const_iterator iterator_type;
  16.     iterator_type begin = std::begin(INPUT_DATA);
  17.     iterator_type end   = std::end(INPUT_DATA);
  18.  
  19.     namespace qi    = boost::spirit::qi;
  20.     namespace ascii = boost::spirit::qi::ascii;
  21.     namespace phx   = boost::phoenix;
  22.  
  23.     bool ok;
  24.     double result;
  25.     {
  26.         using namespace qi;
  27.  
  28.         auto parser = 
  29.                double_                  [_val  = _1]
  30.             >> *(   (lit('+') >> double_[add_(_val, _1)])
  31.                   | (lit('-') >> double_[sub_(_val, _1)])
  32.                 );
  33.  
  34.         ok = phrase_parse(begin, end, parser, ascii::space, result);
  35.     }
  36.  
  37.     if (ok  && begin == end)
  38.         std::cout << "parsed, result = " << result << std::endl;
  39.     else
  40.         std::cout << "not parsed" << std::endl;
  41. }
  42.  
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https://ideone.com/vvQFLX
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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