computer-science

My understanding is that a hash code and checksum are similar things - a numeric value, computed for a block of data, that is relatively unique. i.e. The probability of two blocks of data yielding the same numeric hash/checksum value is low enough that it can be ignored for the purposes of the application. So do we have two words for the same thing, or are there important differences between hash codes and checksums? I would say that a checksum is necessarily a hashcode . However, not all hashcodes make good checksums. A checksum has a special purpose --- it verifies or checks the integrity of

The question of whether P=NP is perhaps the most famous in all of Computer Science. What does it mean? And why is it so interesting? Oh, and for extra credit, please post a proof of the statement's truth or falsehood. :) P stands for polynomial time. NP stands for non-deterministic polynomial time. Definitions: Polynomial time means that the complexity of the algorithm is O(n^k), where n is the size of your data (e. g. number of elements in a list to be sorted), and k is a constant. Complexity is time measured in the number of operations it would take, as a function of the number of data items

It's been a few years since my computer-language class and so I've forgotten the finer points of BNF's and EBNF's and I don't have a textbook next to me. Specifically, I've forgotten how to convert an EBNF into BNF. From what little I remember, I know that one of the main points is to convert { term } into <term> | <many-terms> . But I don't remember the other rules. I've tried to look this up online but I can only find links to either homework questions, or a small comment about converting terms with curly braces. I can't find an exhaustive list of rules that define the translation. 500 -

Isn't a three state object immedately capable of holding more information and handling larger values? I know that processors currently use massive nets of XOR gates and that would need to be reworked. Since we are at 64 bit (we can represent 2^63 possible states) computing the equivalent ternary generation could support number with 30 more tens places log(3^63-2^63). I imagine it is as easy to detect the potential difference between +1 and 0 as it is between -1 and 0. Would some compexity of the hardware, power consumption, or chip density offset any gains in storage and computing power?

This question already has an answer here: What is a predicate? 11 answers Specifically I've seen it used in the context of text filtering. As if "predicate" == "filter criteria". Is this accurate? Prasoon Saurav It is a term most commonly used in the field of Mathematical Logic. From wikipedia In mathematics, a predicate is either a relation or the boolean-valued function that amounts to the characteristic function or the indicator function of such a relation. A function P: X→ {true, false} is called a predicate on X. When P is a predicate on X, we sometimes say P is a property of X. .

I have a rough idea about what this is but if someone has an explanation of the 'expression problem' that they think is succinct and intuitive I would love to hear it. Watch this lecture . The idea is that your program is a combination of a datatype and operations over it. The problem asks for an implementation that allows to add new cases of the type and new operations without the need for recompilation of the old modules and keeping static type safety(no casts or runtime type checks). It's interesting to notice that in functional programming languages it's easy to add new operations, but