antlr4

I want to write a lexer rule about the month and the year, the rule is(with regular expression): "hello"[0-9]{1,2}"ever"([0-9]{2}([0-9]{2})?)? the "hello" and "ever" literals are just for debuging. that's say, one or two digits for month, and two or four digits for year. And what's more, the year part could be bypass. such as: Aug 2015 ->hello08ever2015 or hello8ever2015 or hello8ever15 or hello8ever or hello08ever; Oct 2015 -> hello10ever2015 or hello10ever15 or hello10ever; and my lexer rules are as follow(ANTLR4): grammar Hello; r : 'hello' TimeDate 'ever' TimeYear? ; TimeDate : Digit Digit

I'm developing a simple calculator with the formula grammar: grammar Formula ; expr : <assoc=right> expr POW expr # pow | MINUS expr # unaryMinus | PLUS expr # unaryPlus | expr PERCENT # percent | expr op=(MULTIPLICATION|DIVISION) expr # multiplyDivide | expr op=(PLUS|MINUS) expr # addSubtract | ABS '(' expr ')' # abs | '|' expr '|' # absParenthesis | MAX '(' expr ( ',' expr )* ')' # max | MIN '(' expr ( ',' expr )* ')' # min | '(' expr ')' # parenthesis | NUMBER # number | '"' COLUMN '"' # column ; MULTIPLICATION: '*' ; DIVISION: '/' ; PLUS: '+' ; MINUS: '-' ; PERCENT: '%' ; POW: '^' ; ABS:

I am trying to define lexer rules for PostgreSQL SQL. The problem is with the operator definition and the line comments conflicting with each other. for example @--- is an operator token @- followed by the -- comment and not an operator token @--- In grako it would be possible to define the negative lookahead for the - fragment like: OP_MINUS: '-' ! ( '-' ) . In ANTLR4 I could not find any way to rollback already consumed fragment. Any ideas? Here the original definition what the PostgreSQL operator can be: The operator name is a sequence of up to NAMEDATALEN-1 (63 by default) characters from

I'm using Antlr 4 with c# target. Here is a subset of my grammar: /* * Parser Rules */ text : term+ EOF; term : a1 a2 a3; a1: .... ... ... I want to accept valid data blocks as (term)s, when error exists I want to search for the next valid term and print out the whole text which caused the error for user to analyze manually. How to synchronize input to the next valid term? and How to get the ignored text? You will need to create your own implementation of IAntlrErrorStrategy for this, and then set the Parser.ErrorHandler property to an instance of your error strategy. The documentation for the

I wrote a grammar with antlr 4.4 like this : grammar CSV; file : row+ EOF ; row : value (Comma value)* (LineBreak | EOF) ; value : SimpleValueA | QuotedValue ; Comma : ',' ; LineBreak : '\r'? '\n' | '\r' ; SimpleValue : ~(',' | '\r' | '\n' | '"')+ ; QuotedValue : '"' ('""' | ~'"')* '"' ; then I use antlr 4.4 for generating parser & lexer, this process is successful after generate classes I wrote some java code for using grammar import org.antlr.v4.runtime.ANTLRInputStream; import org.antlr.v4.runtime.CommonTokenStream; public class Main { public static void main(String[] args) { String source

How to match any symbol in ANTLR parser (not lexer)? Where is the complete language description for ANTLR4 parsers? UPDATE Is the answer is "impossible"? You first need to understand the roles of each part in parsing: The lexer: this is the object that tokenizes your input string. Tokenizing means to convert a stream of input characters to an abstract token symbol (usually just a number). The parser: this is the object that only works with tokens to determine the structure of a language. A language (written as one or more grammar files) defines the token combinations that are valid. As you can

As a beginner, when I was learning ANTLR4 from the The Definitive ANTLR 4 Reference book, I tried to run my modified version of the exercise from Chapter 7: /** * to parse properties file * this example demonstrates using embedded actions in code */ grammar PropFile; @header { import java.util.Properties; } @members { Properties props = new Properties(); } file : { System.out.println("Loading file..."); } prop+ { System.out.println("finished:\n"+props); } ; prop : ID '=' STRING NEWLINE { props.setProperty($ID.getText(),$STRING.getText());//add one property } ; ID : [a-zA-Z]+ ; STRING :(~[\r\n]

I was wondering whether we could build an AST using Antlr version 4. I couldn't find any reference on building it using antlr4. One SO answer says that it would be easy to use antlr4 which produces only parse tree but my question is what about the efficiency ? It forces us to crawl whole parse tree instead of an abstract syntax tree which is not efficient way to walk through the whole tree and perform task using visitors. There are two key items I'd like to point out first: Efficiency covers more than simple speed of execution. It can also apply to memory overhead, maintainability, and the