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Antlr Syntax Error


Thank you for posting this, specifically the conditional re-write rules, it was exactly what I was searching for. Grammar: /Users/gpollice/WPI/Compilers/git/gfp-compilers/Base_Dijkstra/Grammars/Dijkstra.g error(100): /Base_Dijkstra/Grammars/Dijkstra.g:11:1: syntax error: antlr: NoViableAltException([email protected][]) error(100): /Base_Dijkstra/Grammars/Dijkstra.g:11:2: syntax error: antlr: NoViableAltException([email protected][]) |---> @parser::header { error(100): /Base_Dijkstra/Grammars/Dijkstra.g:11:8: syntax error: antlr: MissingTokenException(inserted [@-1,0:0='',<50>,11:7] at :) |---> @parser::header { error(100): However, before we can examine how to implement your own recovery, we need to know something about how ANTLR recovers from mismatch problems. Well, we could of course write a custom method for each parse point, and call it in an action directly after the classMember rule. this contact form

Lexer runs first and splits input into pieces called tokens. Here we look at how ANTLR recovers from the various mismatch cases and what techniques you can use to override or influence that recovery. This is really nice Mar 15, 2013, 7:06:00 PM Antonio Guilherme said... First expression is labeled b, the rest goes to the list a: //flat tree from any number of expressions (including one) binaryAnd: b=expression (AND a+=expression)* If there are no additional arguments, http://www.antlr2.org/doc/err.html

Antlr Parser Get Error

The default exception handler will report an error, sync to the follow set of the rule, and return from that rule. EndDepending on the language you try to create, parser construction may be very easy or difficult. NoViableAltException The parser finds an unexpected token; that is, it finds a token that does not begin any alternative in the current decision. This was very very good!

You signed in with another tab or window. All of the above messages are generated using the getMessage method of the exceptions thrown by ANTLR. As ANTLR parses your grammar it constructs an NFA for each block of alternatives in a rule or subrule. Antlr4 Error Handling Example You can leave a response, or trackback from your own site. 5 Responses to "ANTLR By Example: Part 5: Extra Credit" August 9th, 2006 at 12:12 am Ibrahim says: Hi!

For example, this lexer rule matches salutation 'Hello': SALUTATION: 'Hello'; Use '|' to express alternatives. Specifying Parser Exception-Handlers You may attach exception handlers to a rule, an alternative, or a labeled element. Imagine grammar containing lists of letters. http://stackoverflow.com/questions/10386499/handling-antlr-syntax-errors-or-how-to-give-a-better-message-on-unexpected-token matches otherexpression to the rule beginning first.

considering the DRY violation, have you tried class MyParser extends Parser; options { importVocab=V; } ANTLR will now look for VTokenTypes.txt in the current directory and preload the token manager for Antlr Error Handling Basic AST ModificationsWhile previous grammar parses all needed expressions, the result tree leaves a lot to be desired. In fact, all we need do is utilize a simple trick, which is perfectly 'legal' and will do all the calculations for us. Lexer rule matching anything except a digit: NOT_A_DIGIT: ~('0'..'9'); How Lexer WorksIf we ignore details, lexers algorithm is very simple.

Antlr Recover From Mismatched Token

in front of each argument: //the function neither(p1, p2, ..., pn) is equivalent to !p1 && !p2 && ... && !pn neitherFunction : NEITHER LPAREN b=andexpression (',' a+=andexpression)* RPAREN //if the https://theantlrguy.atlassian.net/wiki/display/ANTLR3/Custom+Syntax+Error+Recovery How do I programmatically generate an entity form? Antlr Parser Get Error It now only remains to sync the input stream to this set within our empty rule. Antlr Error Listener Example The rule expression in Hello Word grammar:SALUTATION:'Hello word'; ENDSYMBOL:'!'; expression : SALUTATION ENDSYMBOL; is unambiguous.

void syntaxError(Recognizerrecognizer, ObjectoffendingSymbol, intline, intcharPositionInLine, Stringmsg, RecognitionExceptione) Upon syntax error, weblink First, if you do nothing, ANTLR will generate a default exception handler for every parser rule. Each full-context prediction which does not result in a syntax error will call either reportContextSensitivity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, int, org.antlr.v4.runtime.atn.ATNConfigSet) or reportAmbiguity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, boolean, java.util.BitSet, org.antlr.v4.runtime.atn.ATNConfigSet). This would of course require throwing an exception on inline recovery, so I am suggesting that your cited documentation would change (for the better). Antlr4 Error Handling

Case 1: Unrecognised word: $ java NotifyConditionParserTest "changed or tuer" Caught error: unexpected token: tuer Case 2: Unrecognised character: $ java NotifyConditionParserTest "6 and false" Caught error: unexpected char: '6' Case A little madness is the blog of Daniel Ostermeier and Jason Sankey. Z - the First set for ruleY is the set of tokens that show ruleY should be invoked. navigate here For example, the parser for the 'Hello World' grammar:expression : SALUTATION ENDSYMBOL; would validate whether the input token stream contains a SALUTATION token followed by an ENDSYMBOL token.

more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed Antlr4 Throw Exception On Error Method Detail syntaxError voidsyntaxError(Recognizerrecognizer, ObjectoffendingSymbol, intline, intcharPositionInLine, Stringmsg, RecognitionExceptione) Upon syntax error, notify any interested parties. Rosa Parks is a [symbol?] for the civil rights movement?

Under the surface, they are very different.

Besides that, everything explained in this post is language independent. So, how can we implement such a resync? All parser rules throw this exception. Antlrerrorstrategy Generally, you will still call reportError(), unless you wish to suppress the error, but then you can use your own method/algorithm to recover the input point.

INT ; INT : '0'..'9'+ ; When someone enters a numeric value everything is fine, but if they mistakenly type something like 1O (one and capital o) we get a cryptic syntaxError(new SyntaxError(msg, e)); } public void syntaxError(RecognitionException e) { // Do stuff knowing that RecognitionException e unambiguously contains all the information you need. } Here are the InlineRecognitionException and SyntaxError classes: ANTLR Exception Hierarchy ANTLR-generated parsers throw exceptions to signal recognition errors or other stream problems. http://dis-lb.net/error-handling/antlr-better-error-messages.php All Rights Reserved.

It always starts with a left most condition. ANTLR Exception Hierarchy ANTLR-generated parsers throw exceptions to signal recognition errors or other stream problems. Remove the other parameters (aside from "RecognitionException e") in the method signature of ANTLRErrorListener.syntaxError since they will be extraneous and lead to confusion. If you wish to do the same, add following into your grammar: WS : ( ' ' | '\t' | '\r' | '\n' )+ { $channel = HIDDEN; } Parser -

I even took a look at some of the example grammars on the ANTLR website, and noticed that they suffer from a similar problem. This method is not used by lexers. This post explains what is lexer, what is parser and how to write grammar files to generate them.