DEFINITION MODULE CharClass;
(* ASCII character classification (classic ISO-style names). *)

PROCEDURE IsDigit (ch : CHAR) : BOOLEAN;
(* '0'..'9' *)

PROCEDURE IsUpper (ch : CHAR) : BOOLEAN;
(* 'A'..'Z' *)

PROCEDURE IsLower (ch : CHAR) : BOOLEAN;
(* 'a'..'z' *)

PROCEDURE IsAlpha (ch : CHAR) : BOOLEAN;
(* letter *)

PROCEDURE IsSpace (ch : CHAR) : BOOLEAN;
(* space, tab, CR, LF *)

END CharClass.