runtime/tree/TreeAdaptor.as

/*
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 Copyright (c) 2005-2007 Terence Parr
 All rights reserved.

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package org.antlr.runtime.tree {

	import org.antlr.runtime.*;

	/** How to create and navigate trees.  Rather than have a separate factory
	 *  and adaptor, I've merged them.  Makes sense to encapsulate.
	 *
	 *  This takes the place of the tree construction code generated in the
	 *  generated code in 2.x and the ASTFactory.
	 *
	 *  I do not need to know the type of a tree at all so they are all
	 *  generic Objects.  This may increase the amount of typecasting needed. :(
	 */
	public interface TreeAdaptor {
		// C o n s t r u c t i o n

		/** Create a tree node from Token object; for CommonTree type trees,
		 *  then the token just becomes the payload.  This is the most
		 *  common create call.
		 *
		 * 	Override if you want another kind of node to be built.
	     */
		function createWithPayload(payload:Token):Object;

		/** Duplicate a single tree node.
	 	 *  Override if you want another kind of node to be built.
	 	 */
	 	function dupNode(treeNode:Object):Object;

		/** Duplicate tree recursively, using dupNode() for each node */
		function dupTree(tree:Object):Object;

		/** Return a nil node (an empty but non-null node) that can hold
		 *  a list of element as the children.  If you want a flat tree (a list)
		 *  use "t=adaptor.nil(); t.addChild(x); t.addChild(y);"
		 */
		function nil():Object;

    	/** Return a tree node representing an error.  This node records the
    	 *  tokens consumed during error recovery.  The start token indicates the
    	 *  input symbol at which the error was detected.  The stop token indicates
    	 *  the last symbol consumed during recovery.
    	 *
    	 *  You must specify the input stream so that the erroneous text can
    	 *  be packaged up in the error node.  The exception could be useful
    	 *  to some applications; default implementation stores ptr to it in
    	 *  the CommonErrorNode.
    	 *
    	 *  This only makes sense during token parsing, not tree parsing.
    	 *  Tree parsing should happen only when parsing and tree construction
    	 *  succeed.
    	 */
    	function errorNode(input:TokenStream, start:Token, stop:Token, e:RecognitionException):Object;

		/** Is tree considered a nil node used to make lists of child nodes? */
		function isNil(tree:Object):Boolean;

		/** Add a child to the tree t.  If child is a flat tree (a list), make all
		 *  in list children of t.  Warning: if t has no children, but child does
		 *  and child isNil then you can decide it is ok to move children to t via
		 *  t.children = child.children; i.e., without copying the array.  Just
		 *  make sure that this is consistent with have the user will build
		 *  ASTs.  Do nothing if t or child is null.
		 */
		function addChild(t:Object, child:Object):void;

		/** If oldRoot is a nil root, just copy or move the children to newRoot.
		 *  If not a nil root, make oldRoot a child of newRoot.
		 *
		 *    old=^(nil a b c), new=r yields ^(r a b c)
		 *    old=^(a b c), new=r yields ^(r ^(a b c))
		 *
		 *  If newRoot is a nil-rooted single child tree, use the single
		 *  child as the new root node.
		 *
		 *    old=^(nil a b c), new=^(nil r) yields ^(r a b c)
		 *    old=^(a b c), new=^(nil r) yields ^(r ^(a b c))
		 *
		 *  If oldRoot was null, it's ok, just return newRoot (even if isNil).
		 *
		 *    old=null, new=r yields r
		 *    old=null, new=^(nil r) yields ^(nil r)
		 *
		 *  Return newRoot.  Throw an exception if newRoot is not a
		 *  simple node or nil root with a single child node--it must be a root
		 *  node.  If newRoot is ^(nil x) return x as newRoot.
		 *
		 *  Be advised that it's ok for newRoot to point at oldRoot's
		 *  children; i.e., you don't have to copy the list.  We are
		 *  constructing these nodes so we should have this control for
		 *  efficiency.
		 */
		function becomeRoot(newRoot:Object, oldRoot:Object):Object;

		/** Given the root of the subtree created for this rule, post process
		 *  it to do any simplifications or whatever you want.  A required
		 *  behavior is to convert ^(nil singleSubtree) to singleSubtree
		 *  as the setting of start/stop indexes relies on a single non-nil root
		 *  for non-flat trees.
		 *
		 *  Flat trees such as for lists like "idlist : ID+ ;" are left alone
		 *  unless there is only one ID.  For a list, the start/stop indexes
		 *  are set in the nil node.
		 *
		 *  This method is executed after all rule tree construction and right
		 *  before setTokenBoundaries().
		 */
		function rulePostProcessing(root:Object):Object;

		/** For identifying trees.
		 *
		 *  How to identify nodes so we can say "add node to a prior node"?
		 *  Even becomeRoot is an issue.  Use System.identityHashCode(node)
		 *  usually.
		 */
		function getUniqueID(node:Object):int;


		// R e w r i t e  R u l e s

		/** Create a new node derived from a token, with a new token type.
		 *  This is invoked from an imaginary node ref on right side of a
		 *  rewrite rule as IMAG[$tokenLabel] or IMAG[$tokenLabel, "IMAG"].
		 *
		 *  This should invoke createToken(Token).
		 */
		function createFromToken(tokenType:int, fromToken:Token, text:String = null):Object;

		/** Create a new node derived from a token, with a new token type.
		 *  This is invoked from an imaginary node ref on right side of a
		 *  rewrite rule as IMAG["IMAG"].
		 *
		 *  This should invoke createToken(int,String).
		 */
		function createFromType(tokenType:int, text:String):Object;


		// C o n t e n t

		/** For tree parsing, I need to know the token type of a node */
		function getType(t:Object):int;

		/** Node constructors can set the type of a node */
		function setType(t:Object, type:int):void;

		function getText(t:Object):String;

		/** Node constructors can set the text of a node */
		function setText(t:Object, text:String):void;

		/** Return the token object from which this node was created.
		 *  Currently used only for printing an error message.
		 *  The error display routine in BaseRecognizer needs to
		 *  display where the input the error occurred. If your
		 *  tree of limitation does not store information that can
		 *  lead you to the token, you can create a token filled with
		 *  the appropriate information and pass that back.  See
		 *  BaseRecognizer.getErrorMessage().
		 */
		function getToken(t:Object):Token;

		/** Where are the bounds in the input token stream for this node and
		 *  all children?  Each rule that creates AST nodes will call this
		 *  method right before returning.  Flat trees (i.e., lists) will
		 *  still usually have a nil root node just to hold the children list.
		 *  That node would contain the start/stop indexes then.
		 */
		function setTokenBoundaries(t:Object, startToken:Token, stopToken:Token):void;

		/** Get the token start index for this subtree; return -1 if no such index */
		function getTokenStartIndex(t:Object):int;

		/** Get the token stop index for this subtree; return -1 if no such index */
		function getTokenStopIndex(t:Object):int;


		// N a v i g a t i o n  /  T r e e  P a r s i n g

		/** Get a child 0..n-1 node */
		function getChild(t:Object, i:int):Object;

		/** Set ith child (0..n-1) to t; t must be non-null and non-nil node */
		function setChild(t:Object, i:int, child:Object):void;

		/** Remove ith child and shift children down from right. */
		function deleteChild(t:Object, i:int):Object;

		/** How many children?  If 0, then this is a leaf node */
		function getChildCount(t:Object):int;

		/** Who is the parent node of this node; if null, implies node is root.
		 *  If your node type doesn't handle this, it's ok but the tree rewrites
		 *  in tree parsers need this functionality.
		 */
		function getParent(t:Object):Object;
		function setParent(t:Object, parent:Object):void;

		/** What index is this node in the child list? Range: 0..n-1
		 *  If your node type doesn't handle this, it's ok but the tree rewrites
		 *  in tree parsers need this functionality.
		 */
		function getChildIndex(t:Object):int;
		function setChildIndex(t:Object, index:int):void;

		/** Replace from start to stop child index of parent with t, which might
		 *  be a list.  Number of children may be different
		 *  after this call.
		 *
		 *  If parent is null, don't do anything; must be at root of overall tree.
		 *  Can't replace whatever points to the parent externally.  Do nothing.
		 */
		function replaceChildren(parent:Object, startChildIndex:int, stopChildIndex:int, t:Object):void;


		// Code - generator support - TODO place in separate namespace

		/**
		 * Private method used by generated code.  Based on type and number of arguments will call one of:
		 *
		 * 	* createWithPayload
		 *  * createFromToken
		 *  * createFromType
		 */
		function create(... args):Object;
	}
}