IMPLEMENTATION MODULE CharClass;

PROCEDURE IsDigit (ch : CHAR) : BOOLEAN;
BEGIN
  RETURN (ch >= "0") AND (ch <= "9")
END IsDigit;

PROCEDURE IsUpper (ch : CHAR) : BOOLEAN;
BEGIN
  RETURN (ch >= "A") AND (ch <= "Z")
END IsUpper;

PROCEDURE IsLower (ch : CHAR) : BOOLEAN;
BEGIN
  RETURN (ch >= "a") AND (ch <= "z")
END IsLower;

PROCEDURE IsAlpha (ch : CHAR) : BOOLEAN;
BEGIN
  RETURN IsUpper(ch) OR IsLower(ch)
END IsAlpha;

PROCEDURE IsSpace (ch : CHAR) : BOOLEAN;
BEGIN
  RETURN (ch = " ") OR (ch = CHR(9)) OR (ch = CHR(13)) OR (ch = CHR(10))
END IsSpace;

END CharClass.