Strictly local languages, Theory of Computation

While the SL2 languages include some surprisingly complex languages, the strictly 2-local automata are, nevertheless, quite limited. In a strong sense, they are almost memoryless-the behavior of the automaton depends only on the most recent symbol it has read.

Certainly there are many languages of interest that are not SL2, that will require a more sophisticated algorithm than strictly 2-local automata.

One obvious way of extending the SL2 automata is to give them more memory. Consider, for instance, the language of algebraic expressions over decimal integer constants in which we permit negative constants, indicated by a pre?x ‘-'. Note that this is not the same as allowing ‘-' to be used as a unary operator. In the latter case we would allow any number of ‘-'s to occur in sequence (indicating nested negation), in the case in hand, we will allow ‘-'s to occur only singly (as either a subtraction operator or a leading negative sign) or in pairs (as a subtraction operator followed by a leading negative sign). We will still forbid embedded spaces and the use of ‘+' as a sign.

This is not an SL2 language. If we must permit ‘--' anywhere, then we would have to permit arbitrarily long sequences of ‘-'s. We can recognize this language, though, if we widen the automaton's scanning window to three symbols.

Posted Date: 3/22/2013 1:17:52 AM | Location : United States







Related Discussions:- Strictly local languages, Assignment Help, Ask Question on Strictly local languages, Get Answer, Expert's Help, Strictly local languages Discussions

Write discussion on Strictly local languages
Your posts are moderated
Related Questions
The SL 2 languages are speci?ed with a set of 2-factors in Σ 2 (plus some factors in {?}Σ and some factors in Σ{?} distinguishing symbols that may occur at the beginning and en



Suppose A = (Σ, T) is an SL 2 automaton. Sketch an algorithm for recognizing L(A) by, in essence, implementing the automaton. Your algorithm should work with the particular automa

how to write program Minimum Cost Calculation - Vogel Approximation Method(VAM

We represented SLk automata as Myhill graphs, directed graphs in which the nodes were labeled with (k-1)-factors of alphabet symbols (along with a node labeled ‘?' and one labeled

what exactly is this and how is it implemented and how to prove its correctness, completeness...

Can v find the given number is palindrome or not using turing machine

In Exercise 9 you showed that the recognition problem and universal recognition problem for SL2 are decidable. We can use the structure of Myhill graphs to show that other problems

proof ogdens lemma .with example i am not able to undestand the meaning of distinguished position .