Although the general case is undecidable, many people still do solve problems that are equivilent well enough for day to day use. In cohen's phd thesis on computer viruses, he showed how virus scanning is equivilent to the halting problem, yet we have an entire industry based around this challenge. I also have seen microsoft's terminat...
What is a Turing machine and why do people keep mentioning it? My IBM PC is all I need to do my computation! Why does anyone care about these machines? ...
I was recently reading about artificial life and came across the statement, "Conway’s Game of Life demonstrates enough complexity to be classified as a universal machine." I only had a rough understanding of what a universal machine is, and Wikipedia only brought me as close to understanding as Wikipedia ever does. I wonder if anyone cou...
Stephen Wolfram gave a fascinating talk at TED about his work with Mathematica and Wolfram Alpha. Amongst other things, he pointed out how very simple computations can yield extremely complex behaviors. (He goes on to discuss his ambition for computing the entire physical universe. Say what you will, you gotta give the guy some credit fo...
From wikipedia: "A problem H is NP-hard if and only if there is an NP-complete problem L that is polynomial time Turing-reducible to H (i.e., L ≤ TH)." Why does the problem(call it W) being reduced from need to be NP-complete? Why can't it just also be NP-hard? It seems like what you care about W being "hard" not that its in NP. Though...
Are there limitation to rebol parse function power ? Would it be capable of parsing the whole css2 / css 3 spec or will it encounter theorical impossibility to form some rules ? Update after HostileFork answer: I mean in regexp I think it would be rather impossible, is parse much more powerfull ? If yes does it mean it would be possibl...
XOR encryption is known to be quite weak. But how weak is it if I have a key that is made up of multiple keys of different (ideally prime) lengths which are combined to make a longer key. eg I have a text keys of length 5, 9 and 11. If I just apply the first key using XOR encryption then it should be easy to break as the encryption byte ...
Hi everyone, I'm working my way thorugh a book on computation (Minksy 1967) and am having a hard time with relating a recursive function to a function defined in terms of loops. Specifically he asks to find the relationship between two functions: The Ackermann function (all code in python): def a(n,m): if n==0: return m+1...
Hi, The numerical operations we do in our programs are limited by the number of bytes that a language specifies for a given datatype (or maybe hardware supports). Say I can use integer to do calculations on my paycheck (even "short" is more than enough for a year's earning!!! ;) ) but can't do the same with Bill Gates wealth. So, we go ...