I know that some of the capabilities of the Perl regular expression engine are not regular. However, what class is it? It might be context-free, but CS theory was never my strongest subject. ...
What s the difference between a recursive set and recursive function? ...
Can we compute a sort of distance between regular expressions ? The idea is to mesure in which way two regular expression are similar. ...
Please help me find a grammar or automaton to decide the following language: anbncn where n≥1 ...
If you look at the call stack of a program and treat each return pointer as a token, what kind of automata is needed to build a recognizer for the valid states of the program? As a corollary, what kind of automata is needed to build a recognizer for a specific bug state? (Note: I'm only looking at the info that could be had from this f...
I'm trying to learn about shift-reduce parsing. Suppose we have the following grammar, using recursive rules that enforce order of operations, inspired by the ANSI C Yacc grammar: S: A; P : NUMBER | '(' S ')' ; M : P | M '*' P | M '/' P ; A : M | A '+' M | A '-' M ; And we want to parse ...
Hello! What does it mean that a programming language is a formal programming language? And which languages are formal programming languages? And which are informal programming languages? I haven't found a good explanation yet. ...
Hi, I'm trying to learn some aspects of the Chomsky Hierarchy which are related to programming languages, and i still have to read the Dragon Book. I've read that most programming languages can be parsed as a context free grammar (CFG). In term of computational power, it equals the one of a pushdown non deterministic automaton. Am I rig...
In Chomsky's hierarchy, the set of recursive languages is not defined. I know that recursive languages are a subset of recursively enumerable languages and that all recursive languages are decidable. What I'm curious about is how recursive languages compare to context-sensitive languages. Can I assume that context-sensitive languages ar...
Long time admirer first time inquirer :) I'm working on a program which derives a deterministic finite-state automata from a context-free grammar, and the paper I have been assigned which explains how to do this keeps referring to "arbitrary probabilistic context-free grammars" but never defines the meaning of "arbitrary" in relation to...
JSON and XML are both frequently called to be context-free languages - they are both specified mainly by a formal grammar in EBNF. However this is only true for JSON as defined in RFC 4329, section 2.2 which does not require uniqueness of object keys (many may not know but {"a":1,"a":2} is valid JSON!). But if you require unique keys in ...
Consider the following regular expressions: 7+ (7)+ Does anyone that is very familiar with regular expression theory in Mathematics agree that the two regular expressions are semantically the same? ...
Hi there, I know this question is really stupid but I would really appreciate it if someone can help me out. Q: When you are proving a language is decidable, what are you effectively doing? Thank you ...