#include <iostream>
#include <iterator>
#include <string>
#include <regex>
 
void test(std::string const& data)
{
   std::cout << "Input string: " << data << std::endl;
 
   std::regex reg("((pi|e|x|([-]?[0-9]*[.]?[0-9]+)){2,})");
   auto tokens_begin = std::sregex_iterator(data.begin(), data.end(), reg);
   auto tokens_end = std::sregex_iterator();
   for (std::sregex_iterator i = tokens_begin; i != tokens_end; ++i)
   {
      std::smatch match = *i;
      std::string match_str = match.str();
      std::cout << "Match:  " << match_str << '\n';
   }
 
   std::cout << std::endl;
}
 
int main()
{
   test("piex14.3");
   test("14e");
   test("12.5pi");
   test("ex");
}
 

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