text: #ifndef STRINGTOOLS_CHARTOOLS_H
  #define STRINGTOOLS_CHARTOOLS_H
  
  #include <string>
  
  /* Handy utensils to manipulate characters */
  
  class CharTools {
  public:
      //! Checks whether or not `c` is a vowel. You can define custom vowel characters.
      static bool IsVowel(const char c, const std::string &vowels = "euioay");
  
      //! Returns whether or not `c` is a letter.
      static bool IsLetter(const char c);
  
      //! Returns whether or not `c` is a digit.
      static bool IsDigit(const char c);
  
      //! Checks whether or not `c` is an uppercase character.
      static bool IsUpper(const char c);
  
      //! Checks whether or not `c` is a lowercase character.
      static bool IsLower(const char c);
  
      //! Will return `c` as an uppercase character.
      static char MakeUpper(char c);
  
      //! Will return `c` as a lowercase character.
      static char MakeLower(char c);
  
      //! Will return `c` with the same capitalization as `sign`.
      static char CopySign(char sign, char c);
  };
  
  #endif //STRINGTOOLS_CHARTOOLS_H
  