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  1. #include <regex>
  2. #include <string>
  3. #include <iostream>
  4. using namespace std;
  5.  
  6. int main()
  7. {
  8. 	std::string pat = "^\\s*"  // optional whitespace at the start, then
  9. 		"([-+]?)"              // an optional sign, then
  10. 		"(?=\\.?\\d)"          // lookahead for digit or .digit
  11. 		"(\\d*)"               // numerator (possibly empty)
  12. 		"(?:"                  // followed by
  13. 		   "(?:/(\\d+))?"      // an optional denominator
  14. 		"|"                    // or
  15. 		   "(?:\\.(\\d*))?"    // an optional fractional part
  16. 		   "(?:E([-+]?\\d+))?" // and optional exponent
  17. 		")"
  18. 		"\\s*$";               //  and optional whitespace to finish
  19. 	std::regex e(pat);
  20. 	std::string s(" -23/34 ");
  21. 	std::smatch a;
  22. 	if (std::regex_search(s, a, e))
  23.     	std::cout << a[0] << endl;
  24.  
  25. }
Success #stdin #stdout 0s 15336KB
comments ()
stdin 
Standard input is empty
stdout 
 -23/34
https://ideone.com/xJYlLF
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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