grammar

I used ANTLR version 4 for creating compiler.First Phase was the Lexer part. I created "CompilerLexer.g4" file and putted lexer rules in it.It works fine. CompilerLexer.g4: lexer grammar CompilerLexer; INT : 'int' ; //1 FLOAT : 'float' ; //2 BEGIN : 'begin' ; //3 END : 'end' ; //4 To : 'to' ; //5 NEXT : 'next' ; //6 REAL : 'real' ; //7 BOOLEAN : 'bool' ; //8 . . . NOTEQUAL : '!=' ; //46 AND : '&&' ; //47 OR : '||' ; //48 POW : '^' ; //49 ID : [a-zA-Z]+ ; //50 WS : ' ' -> channel(HIDDEN) //50 ; Now it is time for phase 2 which is the parser.I created "CompilerParser.g4" file and putted grammars

I have a small custom scripting language, and I am trying to update it to allow boolean expressions such as a > 2 and a > 2 and (b < 3 or c > 5) . It's the parenthetical expressions that I am having trouble with here. Here is a (edited since the original post based on the answer from @Bart Kiers) full grammar that exhibits the problem. This is a pared-down version of my actual grammar, but the problem occurs here too. grammar test; options { language = 'JavaScript'; output = AST; } statement : value_assignment_statement EOF ; value_assignment_statement : IDENT '=' expression ; value_expression

I have the following simple expression parser: expr(+(T,E))-->term(T),"+",expr(E). expr(T)-->term(T). term(*(F,T))-->factor(F),"*",term(T). term(F)-->factor(F). factor(N)-->nat(N). factor(E)-->"(",expr(E),")". nat(0)-->"0". nat(1)-->"1". nat(2)-->"2". nat(3)-->"3". nat(4)-->"4". nat(5)-->"5". nat(6)-->"6". nat(7)-->"7". nat(8)-->"8". nat(9)-->"9". However this only supports 1-digit numbers. How can I parse numbers with multiple digits in this case? Use accumulator variables, and pass those in recursive calls. In the following, A and A1 are the accumulator. digit(0) --> "0". digit(1) --> "1". %

Namely, is there a tool out there that will automatically show the full language for a given grammar, including highlighting ambiguities (if any)? There might be some peculiarity about BNF-style grammars, but in general, deciding whether a given context-free grammar (such as BNF) is ambiguous is not possible. In short, there does not exist a tool because in general, that tool is mathematically impossible. There might be some special cases that could work for you, though. In general, no. But as a practical approach, what you can do, is given a grammar, is for each rule, to enumerate possible

This question is inspired by Is sizeof(void()) a legal expression? but with an important difference as explained below. The expression in question is: sizeof( int() ) In the C++ grammar there appears: unary-expression: sizeof unary-expression sizeof ( type-id ) however, ( int() ) can match both of these cases with different meanings: As a unary-expression , it is a value-initialized int prvalue, surrounded in redundant parentheses As a type-id , it is the type of a function with no parameters returning int . In the semantic constraints for sizeof , i.e. C++14 [expr.sizeof]/1, it explains that

This is a typescript interface: interface A { l: { x: string; y:number } } But this (similar thing) produces an error: interface A { l: { x: string, y:number } } // => Error: ';' expected. On p.37 of the spec: http://www.typescriptlang.org/Content/TypeScript%20Language%20Specification.pdf I see that indeed it is specified that a ; should appear there, but coming from JavaScript the semicolon in the middle of the object-literal-ish thing looks wrong. Was this decision made to avoid ambiguity in the parser, or for some other reason? As of TypeScript 1.6 or so, you can now use either , or ; as a

I am currently trying to make my java code (using eclipse) perform some function if a certain thing is said. I am using the Sphinx4 libraries and this is what I currently have: What I would like it to do is at the line where it says: IF (TRUE) someFunction(); is to run the function if my speech is Hello Computer, Hello Jarvis, Good Morning Computer, or Good Morning Jarvis. Or in other words, run the function if the speech matches the "public < greet >" line of code in the .gram file. Even more specific, return "greet" if my speech corresponds with that grammar rule. I am sorry if this doesnt