Lexeme class

Often we wish to group a set of lexemes together into lexeme classes if they logically behave in some uniform manner; for example, if they act uniformly in a lexical rule. By grouping related lexemes together into a class we can refer to them succinctly by their class name.

The syntax of a lexeme class declaration is

Lexeme_Class_Decl	::=	lexeme class Lexeme_Class_Eq and ¼ and Lexeme_Class_Eq ;
Lexeme_Class_Eq	::=	Id = Lexeme_Spec  - ¼ - Lexeme_Spec
Lexeme_Spec	::=	String
	|	Id Regexp

The following example, the lexeme classes MainKeywords, Symbols, and Literals are defined.

lexeme class MainKeywords =
    "rewrite" | "inference" | "match" | "matchall" | "matchscan"
  | "refine"  | "classof" | "type" | "datatype" | "instantiate"
  | "lexeme"  | "bitfield" | "begin" | "syntax"
  | "dataflow" | "module" | "signature" | "constraint" | "declare"
  | "procedure" | "fun" | "function" | "domain"
  | "graphtype" | "graphrewrite"

and  Symbols =
    ".." | "..." | "<->" | "::" | "&&" | "||" | "++" | "--" | "->"
  | "<<" | ">>" | ">=" | "<=" | "+=" | "-=" | "*=" | "/=" | "%=" | "=="
  | "!=" | "<<=" | ">>=" | "&=" | "|=" | "^=" | "=>" | "<-" | "<=>"
  | ":=" | ":-" | LONG_BAR /\-\-\-\-\-+/

and Literals =
    INT_TOK     /{integer}/
  | REAL_TOK    /{real}/
  | CHAR_TOK    /{character}/
  | STRING_TOK  /{string}/
  ;