 }
 
 
+/**
+ * Accumulates a string representation of an AST and otherwise passes the
+ * AST unfiltered.  The result is an array of Strings, each representing a line
+ * of output.  For plaintext tracing, the lines array should be joined with "\n"
+ */
 class ASTDumper extends ASTFilter
 {
     public var lines:Array = [ ];

}


class VirtualGetResolver extends ASTFilter
{
    private var _axis:String;

}


/**
 * Returns the value of a register.
 */
class GetRegister implements ASTNode
{
    public var regv:Vector.<Number>;
