m3tk/src/gast/ASTCopy.i3

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 ASTCopy provides a way to copy all or part of an AST. 


INTERFACE ASTCopy;

IMPORT AST, ASTWalk;

TYPE
  Closure <: Closure_public;
  Closure_public = OBJECT
  METHODS
    callback(n, ncopy: AST.NODE;
             vm: ASTWalk.VisitMode) RAISES ANY;
    init(): Closure;
  END;

PROCEDURE Nodes(
    n: AST.NODE;
    ): AST.NODE RAISES {};

 Copies the tree rooted at n and returns the root of the copy. 

PROCEDURE ModeNodes(
    n: AST.NODE;
    c: Closure;
    vm : ASTWalk.VisitModeControl;
    ): AST.NODE RAISES ANY;

 Similar to Nodes but supports a per-node callback. 

PROCEDURE IgnoreChildren(c: Closure) RAISES {};

 Suppress the copy of the children of the current node. 

END ASTCopy.

 The ASTCopy interface allows an AST to be copied, with provision
for the caller to be called back at each node, using a similar
mechanism to the ASTWalk interface. The callback can be used to copy
or share additional attributes that are not copied by the underlying
copy method, for example attributes that cause the AST to form a
graph rather than a tree. 


The Nodes procedure provides for a simple copy of the tree rooted at
its argument, n, without any callbacks.


The ModeNodes takes a closure argument that should be created with a
call of NEW(Closure, callback := YourCallback).init(). The closure can be
subtyped to provide for shared state to be accessed during the
callbacks. The vm argument can be used to control when the callback
are made in the way described in the ASTWalk interface. On an
{\em entry} callback to a node, the value of the ncopy will be NIL.
On an {\em exit} callback, ncopy will refer to the newly created copy.


The IgnoreChildren procedure can be called to suppress the copying
of a node's children. Once control leaves the node from which the call
was made, the suppression is disabled. It is only effective when
called in {\em entry} mode.