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Questions tagged [grammar]

A formal grammar is a set of production rules that describe how to form strings of valid syntax. Formal Grammars are most often used to specify the syntax of a programming language.

A formal grammar is a set of production rules that describe how to form strings of valid syntax. Formal Grammars are most often used to specify the syntax of a programming language.

A grammar is formally defined as a 4-tuple, consisting of a series of production rules, terminal symbols, nonterminal symbols, and a start symbol, which itself is a nonterminal. Any terminal cannot be a nonterminal and vice-versa.

Grammars prove very useful in parsers for programming languages. A grammar can be used to determine the syntactical correctness of a given string.

Parser generators such as JavaCC or ANTLR use a given grammar (usually one of a particular form, and free of ambiguities) to generate the parser.

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Left-factoring a non-left-recursive grammar to make it LL(1)

I have removed left-recursion from a left-recursive grammar given to me. The original grammar is as follows: SPRIME::= Expr eof Expr::= Term | Expr + Term | Expr - Term Term::= Factor | Term * Factor | Term / Factor | Term mod Factor | Term div…
Richard Stokes
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Failing to generate S=>Ba from python code given

Given S=>BaB, B=>b and null(B), the code is supposed to generate S=>BaB|aB|Ba|a and B=>b but it is not generating Ba i.e the output is S=>BaB|aB|a and B=>b which is not correct. The code can generate values correctly if terminal is not in the middle…
skyridertk
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When would a parser append its input string?

Given a parser newtype Parser a = Parser { parse :: String -> [(a,String)] } (>>=) :: Parser a -> (a -> Parser b) -> Parser b p >>= f = Parser $ \s -> concat [ parse (f a) s' | (a, s') <- parse p s ] return :: a -> Parser a return a = Parser (\s…
Micha Wiedenmann
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Why bison does not convert grammar automatically?

I am learning lexer and parser, so I am reading this classical book : flex & bison (By John Levine, Publisher: O'Reilly Media). An example is given that could not be parsed by bison : phrase : cart_animal AND CART | work_animal AND…
Stef1611
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antlr grammar: Allow whitespace matching only in template string

I want to parse template strings: `Some text ${variable.name} and so on ... ${otherVariable.function(parameter)} ...` Here is my grammar: varname: VAR ; variable: varname funParameter? ('.' variable)* ; templateString: '`' (TemplateStringLiteral*…
Martin Cup
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Is it normal for some C expressions allowed in its grammar, not to be allowed when compiled in practice?

I was studying the C grammar: http://www.quut.com/c/ANSI-C-grammar-y-1999.html#unary-expression There's this rule assignment_expression : conditional_expression | unary_expression assignment_operator assignment_expression ; And unary_expression :…
Tiago Oliveira
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How to design a context free grammar that avoids repetition?

I am learning about context-free grammar and I would like to know how (if at all) it is possible to design a language that avoids repetition. Let's take the select statement from SQL as an example: possible: SELECT * FROM table SELECT * FROM…
User12547645
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Grammar LaTeX like with mixed whitespace utf and commands

I've tried to implement a LaTeX like grammar that could allow me to parse this kind of sentence : \title{Un pré é"'§è" \VAR state \draw( 200\if{expression kjlkjé} ) bis tèr } As you can see, the \title{ } can contain several kind of items : string…
chrisb06
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Is it possible to dynamically add "keywords" in VS Code syntax highlighting?

I've been playing around with syntax highlighting in VS Code and have so far been able to get a pretty good result using a custom JSON TextMate grammar. Although an extension already existed for GCC ARM Assembly, I thought it sucked, so I used the…
Aaron Beaudoin
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Ambiguous Regular Grammar?

Does such a thing exist? If so, could you please provide an example? Thanks.
Bob Dole
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Yacc parser grammar bug. int X; read separately as int X and ;

Problem Description In my yacc parser grammar, I have the following rules and corresponding actions defined (see program.y below). Parsing int X; should have the derivation type => TOK_INT and variable_list => TOK_VARIABLE, and then these match…
foobuzz
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How do I figure out ANTLR grammar failure to parse input, special timestamp in logfile

INPUT: Mar 9 10:19:07 west info tmm1[17280]: 01870003:6: /Common/mysaml.app/mysaml:Common:00000000: helloasdfasdf asdfadf vgnfg GRAMMAR: grammar scratch; lines : datestamp hostname level proc msgnum module msgstring; datestamp: …
Joel D
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ANTLR grammar: Add "dynamic" proximity operator

For a study project, I am using the following ANTLR grammar to parse query strings containing some simple boolean operators like AND, NOT and others: grammar SimpleBoolean; options { language = CSharp2; output = AST; } tokens { AndNode;…
Shackles
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Lemon Parser REPL

I'm trying to build a Smalltalk REPL based on LanguageKit, which uses a lemon gramma. Currently the parser only supports parsing complete class definitions, but not statements outside of the method syntax. For example this gets parsed: methodName…
catlan
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How can I find regular grammar for L* if we are given a grammar for language L?

Is there any general method to do so? For example, we have a general method to find grammar for L1 U L2 by adding a production S-> S1 | S2 where S1 and S2 are start symbols for grammars of L1 and L2 respectively. Thanks in advance..
Aadish Jain
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