Package org.antlr.runtime.tree

Class TreeParser

  • Direct Known Subclasses:
    DebugTreeParser, TreeFilter, TreeRewriter
    public class TreeParser
extends BaseRecognizer
    A parser for a stream of tree nodes. "tree grammars" result in a subclass of this. All the error reporting and recovery is shared with Parser via the BaseRecognizer superclass.

    • Method Detail

      • reset

        public void reset()
        Description copied from class: BaseRecognizer
        reset the parser's state; subclasses must rewinds the input stream
        Overrides:
        reset in class BaseRecognizer

      • setTreeNodeStream

        public void setTreeNodeStream​(TreeNodeStream input)
        Set the input stream

      • getCurrentInputSymbol

        protected Object getCurrentInputSymbol​(IntStream input)
        Description copied from class: BaseRecognizer
        Match needs to return the current input symbol, which gets put into the label for the associated token ref; e.g., x=ID. Token and tree parsers need to return different objects. Rather than test for input stream type or change the IntStream interface, I use a simple method to ask the recognizer to tell me what the current input symbol is. This is ignored for lexers.
        Overrides:
        getCurrentInputSymbol in class BaseRecognizer

      • getMissingSymbol

        protected Object getMissingSymbol​(IntStream input,
                                  RecognitionException e,
                                  int expectedTokenType,
                                  BitSet follow)
        Description copied from class: BaseRecognizer
        Conjure up a missing token during error recovery. The recognizer attempts to recover from single missing symbols. But, actions might refer to that missing symbol. For example, x=ID {f($x);}. The action clearly assumes that there has been an identifier matched previously and that $x points at that token. If that token is missing, but the next token in the stream is what we want we assume that this token is missing and we keep going. Because we have to return some token to replace the missing token, we have to conjure one up. This method gives the user control over the tokens returned for missing tokens. Mostly, you will want to create something special for identifier tokens. For literals such as '{' and ',', the default action in the parser or tree parser works. It simply creates a CommonToken of the appropriate type. The text will be the token. If you change what tokens must be created by the lexer, override this method to create the appropriate tokens.
        Overrides:
        getMissingSymbol in class BaseRecognizer

      • matchAny

        public void matchAny​(IntStream ignore)
        Match '.' in tree parser has special meaning. Skip node or entire tree if node has children. If children, scan until corresponding UP node.
        Overrides:
        matchAny in class BaseRecognizer

      • getErrorHeader

        public String getErrorHeader​(RecognitionException e)
        Prefix error message with the grammar name because message is always intended for the programmer because the parser built the input tree not the user.
        Overrides:
        getErrorHeader in class BaseRecognizer

      • inContext

        public boolean inContext​(String context)
        Check if current node in input has a context. Context means sequence of nodes towards root of tree. For example, you might say context is "MULT" which means my parent must be MULT. "CLASS VARDEF" says current node must be child of a VARDEF and whose parent is a CLASS node. You can use "..." to mean zero-or-more nodes. "METHOD ... VARDEF" means my parent is VARDEF and somewhere above that is a METHOD node. The first node in the context is not necessarily the root. The context matcher stops matching and returns true when it runs out of context. There is no way to force the first node to be the root.

      • inContext

        public static boolean inContext​(TreeAdaptor adaptor,
                                String[] tokenNames,
                                Object t,
                                String context)
        The worker for inContext. It's static and full of parameters for testing purposes.

      • traceIn

        public void traceIn​(String ruleName,
                    int ruleIndex)

      • traceOut

        public void traceOut​(String ruleName,
                     int ruleIndex)