m3tk/src/ast/M3AST_LX.i3

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 Copyright (C) 1993, Digital Equipment Corporation           
 All rights reserved.                                        
 See the file COPYRIGHT for a full description.              


INTERFACE M3AST_LX;

IMPORT M3AST;

 This interface defines the types of the lexical entities in the
Modula-3 AST. At this level of the specification, most of the entities
are declared as opaque types, to be given a definition by a particular
implementation of the AST. The exception is source position
information which is defined as an INTEGER, although the encoding of
the bits is not specified here. 


TYPE
  Symbol_rep <: REFANY;       (* identifiers *)
  Literal_rep <: REFANY;      (* all literals *)
  Number_rep <: Literal_rep;  (* numeric literals *)
  Text_rep <: Literal_rep;    (* text and character literals *)
  SrcPos = INTEGER;           (* source positions *)
  Whitespace_rep <: REFANY;   (* whitespace *)
  BadChar_rep <: REFANY;      (* illlegal character *)
  Comment_rep <: REFANY;      (* a comment *)
  Pragma_rep <: REFANY;       (* a pragma *)
  Token_rep <: REFANY;        (* reserved word or symbol *)

 The AST is capable of recording the complete set of characters that
were present in the original source file, allowing exact reproduction.
The class SRC_NODE is defined to denote a node that represents an
entity in the source form of the program.  The {\it source position}
of any SRC_NODE is available as an attribute, lx_srcpos. The
terminal symbols of the Modula-3 grammar are represented by subtypes
of SRC_NODE, as are whitespace, comments, pragmas, and illegal
characters. 


Nodes that represent non-terminals of the grammer and, therefore have
child nodes, are declared as subtypes of SRC_NODE_C. This class carries a
sequence attribute, lx_node_s, that encodes all the terminals and
child nodes, in the order of occurrence. 


<* PRAGMA FIELDS *>

TYPE
  SRC_NODE <: M3AST.NODE;
  <* FIELDS OF SRC_NODE
       lx_srcpos: SrcPos; *>

  SRC_NODE_C <: SRC_NODE;
  <* FIELDS OF SRC_NODE_T
       lx_node_s: SEQUENCE OF SRC_NODE; *>

  Whitespace <: SRC_NODE;
  <* FIELDS OF Whitespace
       lx_whitespace_rep: Whitespace_rep; *>

  Comment <: SRC_NODE;
  <* FIELDS OF Comment
       lx_comment_rep: Comment_rep; *>

  Pragma <: SRC_NODE;
  <* FIELDS OF Pragma
       lx_pragma_rep: Pragma_rep *>

  BadChar <: SRC_NODE;
  <* FIELDS OF BadChar
      lx_badchar_rep: BadChar_rep *>

  Token <: SRC_NODE;
  <* FIELDS OF Token
       lx_token_rep: Token_rep; *>

 Identifiers are represented by many different node types, all of
which are subtypes of the ID class. This class carries the lexical
attribute that denotes the name of the identifier. 


  
ID <: SRC_NODE;
  <* FIELDS OF ID
    lx_symrep: M3AST_LX.Symbol_rep; *>

 All literals are members of the class LITERAL, which carries the
lexical information. 


  
LITERAL <: SRC_NODE;
  <* FIELDS OF LITERAL
       lx_litrep: Literal_rep; *>

END M3AST_LX.





interface M3AST is in: