m3tk/src/ast/M3ASTScope.i3

 Copyright (C) 1992, Digital Equipment Corporation           
 All rights reserved.                                        
 See the file COPYRIGHT for a full description.              


INTERFACE M3ASTScope;

IMPORT ASTWalk, AST, M3AST_AS, M3AST_SM;

 This interface provides support for managing scopes, in
   terms of the M3AST_SM.SCOPE class. The assumption is
   that a client is using the ASTWalk package to visit
   each node in the AST, on entry and exit. The Set procedure
   should be called each time a node is entered, and this
   will return a SCOPE object that can be used for identifier
   lookups.



TYPE Closure <: Closure_public;
     Closure_public = ASTWalk.Closure OBJECT
    scope: M3AST_SM.SCOPE := NIL;
  END;

 Create a subtype of Closure, with callback bound to
   the procedue that will call Set, and pass it to
   ASTWalk.ModeVisitNodes. 

PROCEDURE Set(cl: Closure; n: AST.NODE; vm: ASTWalk.VisitMode);

 This procedure updates the value of cl.scope according to
   the type of n and the value of vm, (Entry/Exit). 

PROCEDURE Lookup(s: M3AST_SM.SCOPE;
                 used_id: M3AST_AS.USED_ID): M3AST_AS.DEF_ID;

 This procedure tries to bind the identifier occurrence used_id
   to a definition. If the search fails, NIL is returned, else
   the node of the defining occurrence. 

END M3ASTScope.