text: #include "../include/prolog.h"
  
  Prolog* Prolog::_instance = nullptr;
  
  Prolog::Prolog()
  {
  
  }
  
  Prolog* Prolog::getInstance(){
      if (!_instance)
          _instance = new Prolog();
      return _instance;
  }
  
  bool Prolog::isSpecialChar(char c){
      return c == '+' || c == '-' || c == '*' || c == '/' || c == '<' || c == '>' 
      || c == '.' || c == '&' || c == '\\' || c == '~' || c == '^' || c == '$' 
      || c == '#' || c == '@' || c == '?' || c == ':';
  }