LL is usually a more efficient parsing technique than recursive-descent. In fact, a naive recursive-descent parser will actually be O(k^n) (where n is the input size) in the worst case. Some techniques such as memoization (which yields a Packrat parser) can improve this as well as extend the class of grammars accepted by the parser, … Read more
Regular grammar is either right or left linear, whereas context free grammar is basically any combination of terminals and non-terminals. Hence you can see that regular grammar is a subset of context-free grammar. So for a palindrome for instance, is of the form, S->ABA A->something B->something You can clearly see that palindromes cannot be expressed … Read more
A context free grammar is a grammar which satisfies certain properties. In computer science, grammars describe languages; specifically, they describe formal languages. A formal language is just a set (mathematical term for a collection of objects) of strings (sequences of symbols… very similar to the programming usage of the word “string”). A simple example of … Read more
Below is my (current) favorite demonstration of why parsing C++ is (probably) Turing-complete, since it shows a program which is syntactically correct if and only if a given integer is prime. So I assert that C++ is neither context-free nor context-sensitive. If you allow arbitrary symbol sequences on both sides of any production, you produce … Read more