Problem Detail: This is a follow up to the How does Stack Inspection work? that explores the notion in more detail Stack inspection is a mechanism for ensuring security in the context of the JVM and CLR virtual machines when externally Read More …
Author: ignougroup
LR(1) – Items, Look Ahead
Problem Detail: I am having diffuculties understanding the principle of lookahead in LR(1) – items. How do I compute the lookahead sets ? Say for an example that I have the following grammar: S -> AB A -> aAb | b Read More …
Examples of undecidable problems whose intersection is decidable
Problem Detail: I know that given two problems are undecidable it does not follow that their intersection must be undecidable. For example, take a property of languages $P$ such that it is undecidable whether the language accepted by a given pushdown Read More …
Algorithm to match numbers with minimum number of moves
Problem Detail: This is a sort of edit-distance question, and is very easy. I am just quite brain dead on this subject and can’t figure it out so far. Given a series of numbers, e.g. [3, 1, 1, 1] How Read More …
Difference Between Small and Big-step Operational Semantics
Problem Detail: What’s the fundamental difference(s) between small and big-step operational semantics? I’m having a hard time grasping what it is and the motivation for having the two. Asked By : Simon Morgan Answered By : Gilles Small-step semantics defines a method to Read More …
Finding the median in a heap
Problem Detail: Given a binary heap $H$, indexed in $[1..n]$, whose elements are integers, is there a way to quickly find its median in $O(log n)$-time? Asked By : Cássio Jandir Pagnoncelli Answered By : jbapple It takes $Omega(n)$ time to find the Read More …
Clustered index is dense or sparse?
Problem Detail: I am confused about clustered index is dense or sparse. I searched for that, sources saying it is sparse, but can be dense also. What is it exactly? Asked By : user1218927 Answered By : tanmoy Clustering index is applied when Read More …
Why is factoring large integers considered difficult?
Problem Detail: I read somewhere that the most efficient algorithm found can compute the factors in $O(exp((64/9 cdot b)^{1/3} cdot (log b)^{2/3})$ time, but the code I wrote is $O(n)$ or possibly $O(n log n)$ depending on how fast division and Read More …
What are the different types of databases?
Problem Detail: Is there is a study or classification available on different types of databases? (Examples include structured, unstructured, semi structured relational, object oriented, folksonomies, etc.) Asked By : sashank Answered By : Romuald One of the key differences between the different paradigms Read More …
Is $(a^nb^m)^r$ regular?
Problem Detail: I took my theory of computation exams a few weeks ago, and this was one of the questions: Assume language $L={(a^nb^m)^r mid n,m,rge 0}$ Is L regular? If yes provide a regular expression or an automaton for it. After Read More …
