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• Characteristics of an Initialization Vector

  - by Jamie Chapman

  I'm by no means a cryptography expert, I have been reading a few questions around Stack Overflow and on Wikipedia but nothing is really 'clear cut' in terms of defining an IV and it's usage. Points I have discovered: An IV is pre-pended to a plaintext message in order to strengthen the encryption The IV is truely random Each message has it's own unique IV Timestamps and cryptographic hashes are sometimes used instead of random values, but these are considered to be insecure as timestamps can be predicted One of the weaknesses of WEP (in 802.11) is the fact that the IV will reset after a specific amount of encryptions, thus repeating the IV I'm sure there are many other points to be made, what have I missed? (or misread!)

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• C++ method chaining including class constructor

  - by jena

  Hello, I'm trying to implement method chaining in C++, which turns out to be quite easy if the constructor call of a class is a separate statement, e.g: Foo foo; foo.bar().baz(); But as soon as the constructor call becomes part of the method chain, the compiler complains about expecting ";" in place of "." immediately after the constructor call: Foo foo().bar().baz(); I'm wondering now if this is actually possible in C++. Here is my test class: class Foo { public: Foo() { } Foo& bar() { return *this; } Foo& baz() { return *this; } }; I also found an example for "fluent interfaces" in C++ (http://en.wikipedia.org/wiki/Fluent_interface#C.2B.2B) which seems to be exactly what I'm searching for. However, I get the same compiler error for that code. Thanks in advance for any hint. Best, Jean

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• Programming languages: out of the box legibility and extensibility

  - by sova

  Two excellent results of SOLID development ideology are - Legibility - Extensibility over the life of a project (http://en.m.wikipedia.org/wiki/Solid_(object-oriented_design) Although SOLID is a set of language-agnostic design ideas, some languages inherently support these ideas better than others. Out-of-the-box or after various customizations, in your opinion which language is best-suited to be both easily readable and easy to extend functionality in? Some definitions to pre-empt biases and flamewars: Legibility: amount of thinking done to understand the code proportional to the amount of code: (amount_think-energy / amount_code) is fairly constant and as low as possible in the optimal case. Extensibility: Addition of X amount of functionality requires a change in code or code additions in proportion to X (amount_added_functionality / amount_added_code) is fairly constant and as high as possible in the optimal case. Supporting information and tutorials encouraged. Code snippets welcome.

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• Why does tokyo tyrant slow down exponentially even after adjusting bnum?

  - by HenryL

  Has anyone successfully used Tokyo Cabinet / Tokyo Tyrant with large datasets? I am trying to upload a subgraph of the Wikipedia datasource. After hitting about 30 million records, I get exponential slow down. This occurs with both the HDB and BDB databases. I adjusted bnum to 2-4x the expected number of records for the HDB case with only a slight speed up. I also set xmsiz to 1GB or so but ultimately I still hit a wall. It seems that Tokyo Tyrant is basically an in memory database and after you exceed the xmsiz or your RAM, you get a barely usable database. Has anyone else encountered this problem before? Were you able to solve it?

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• Can a user be a member of multiple Organization Units (OU) in Active Directory ?

  - by Stormshadow

  Can a user be a member of multiple Organization Units (OU) in Active Directory ? Also, is there a standard format mentioned by Microsoft on how an OU should be created and what its attributes are ? I found this in Wikipedia "However, Organizational Units are just an abstraction for the administrator, and do not function as true containers; the underlying domain operates as if objects were all created in a simple flat-file structure, without any OUs. It is not possible for example to create two user accounts with an identical username in two separate OUs, such as "fred.staff-ou.domain" and "fred.student-ou.domain"."

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• Question on Simple Look Up Tables [closed]

  - by CVS26

  Hi everyone... I'm doing some research on Simple Look Up Tables. I have : been thru wikipedia. Googled Look-up tables Browsed thedailywtf.com Been thru several websites illustrating/documenting look-up table code. Currently i am looking for any insight anyone can throw on the topic (LuTs). Also, I am specifically looking for any anecdotes one would like to share (again on LuTs). All content will be adequately acknowledge (or anonymised, if requested) in the article. Thank You

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• What's your favorite implementation of producing the fibonacci sequence?

  - by Terry Donaghe

  Best, most creative, most clever, fastest, smallest, written in weirdest language, etc etc. For those not familiar with this staple of programming exam question / interview question, check this out: Fibonacci Sequence at Wikipedia The question would be, write a simple program which will spit out the first n digits of the Fibonacci sequence. So, if n == 12, we produce: 0 1 1 2 3 5 8 13 21 34 55 89 144 Your implementation becomes more interesting when you set n to larger values. How long does it take your implementation to return a 25 digit sequence? How about 100?

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• What are good resources for computer graphics basics?

  - by Hanno Fietz

  During Flex programming, I recently ran into several questions (about box models, ways to join lines and misaligning pixels [on doctype]) regarding computer graphics and layout, where I felt that I lacked some basic background on things like concepts like the box model approaches mapping real numbers to a pixel raster (like font anti-aliasing) conventions found across drawing engines, like do you count y coordinates from top or bottom, and why I feel that reading some basic Wikipedia articles, books or tutorials on these subjects might help in phrasing my questions more specifically and debugging my code more systematically. I have repeatedly found myself writing tiny test apps in Flex, just to find out how the APIs do very basic stuff. My assumption would be that if I knew the right vocabulary and some general concepts, I could solve these questions much faster.

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• What is the difference between remote procedure call and web service

  - by xiao

  Is there any clear definition about RPC and Web Service? A quick wikipedia search shows: RPC: Remote procedure call (RPC) is an Inter-process communication technology that allows a computer program to cause a subroutine or procedure to execute in another address space (commonly on another computer on a shared network) without the programmer explicitly coding the details for this remote interaction. Web Service: Web services are typically application programming interfaces (API) or web APIs that are accessed via Hypertext Transfer Protocol and executed on a remote system hosting the requested services. Web services tend to fall into one of two camps: Big Web Services[1] and RESTful Web Services. I am not quite clear what the real difference between the two things. It seems that one thing could belongs to RPC and is kind of web service at the same time. Is Web Service a higher level representation of RPC?

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• Flow Based Programming

  - by Software Monkey

  I have been doing a little reading on Flow Based Programming over the last few days. There is a wiki which provides further detail. And wikipedia has a good overview on it too. My first thought was, "Great another proponent of lego-land pretend programming" - a concept harking back to the late 80's. But, as I read more, I must admit I have become intrigued. Have you used FBP for a real project? What is your opinion of FBP? Does FBP have a future? In some senses, it seems like the holy grail of reuse that our industry has pursued since the advent of procedural languages.

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• Interview question: difference between object and object-oriented languages.

  - by Bar

  My friend was asked the following question: what's the difference between object language and object-oriented language? It's a little unintelligible question. What does term «object language» correspond to? Does that mean «pure» object-oriented language, like the Wikipedia article says: Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby, JADE, VB.NET.

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• Sprintf equivalent in Mathematica?

  - by jxy

  I don't know why Wikipedia lists Mathematica as a programming language with printf. I just couldn't find the equivalent in Mathematica. My specific task is to process a list of data files with padded numbers, which I used to do it in bash with fn=$(printf "filename_%05d" $n) The closest function I found in Mathematica is PaddedForm. And after some trial and error, I got it with "filename_" <> PaddedForm[ Round@#, 4, NumberPadding -> {"0", ""} ]& It is very odd that I have to use the number 4 to get the result similar to what I get from "%05d". I don't understand this behavior at all. Can someone explain it to me? And is it the best way to achieve what I used to in bash?

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• help implementing algorithm

  - by davit-datuashvili

  http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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• How do I do a semijoin using SQLAlchemy?

  - by Jason Baker

  http://en.wikipedia.org/wiki/Relational_algebra#Semijoin Let's say that I have two tables: A and B. I want to make a query that would work similarly to the following SQL statement using the SQLAlchemy orm: SELECT A.* FROM A, B WHERE A.id = B.id AND B.type = 'some type'; The thing is that I'm trying to separate out A and B's logic into different places. So I'd like to make two queries that I can define in separate places: one where A uses B as a subquery, but only returns rows from A. I'm sure this is fairly easy to do, but an example would be nice if someone could show me.

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• Is Classic ADO still viable for a mixed managed/unmanaged App?

  - by Andy Dent

  We have a complex architecture with much logic in unmanaged code that needs database access. Currently this is via ODBC drivers and MFC classes and we're considering the issues of migrating our abstraction layer to use ADO or ADO.Net. In the latter case we'd have to be pushing database logic back up into the .Net layer. I'm trying to decide if the pain of invoking the database via .Net callbacks is offset by the improvements in ADO.Net. The Wikipedia comparison was interesting although I'm not sure I believe all the points in the comparison table (eg: does ADO.Net always use XML to pass data?). A 2005 comparison shows ADO.Net performing dramatically faster. Microsoft's guide to ADO.Net for ADO programmers suggests we will gain much from going to ADO.Net especially the way that data is available in native (.Net) types rather than solely through OLEAutomation's Variant.

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• how to tesselate bezier triangles?

  - by Cheery

  My concern are quadratic bezier triangles which I'm trying to tesselate for rendering them. I've managed to implement this by subdividing the triangle recursively like described in a wikipedia page. Though I'd like to get more precision to subdivision. The problem is that I'll either get too few subdivisions or too many because the amount of surfaces doubles on every iteration of that algorithm. In particular I would need an adaptive tesselation algorithm that allows me to define the amount of segments at the edges. I'm not sure whether I can get that though so I'd also like to hear about uniform tesselation techniques. Hardest trouble I have trouble with calculating normals for a point in bezier surface, which I'm not sure whether I need, but been trying to solve out.

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• Bash script to (more or less) reliably check if the internet is up

  - by João Portela

  I need a bash script to put in a cron job that every minute checks if the internet is up. This is how I did it: #! /bin/sh host1=google.com host2=wikipedia.org curr_date=`date +"%Y%m%d%H%M"` echo -n "${curr_date};" ((ping -w5 -c3 $host1 || ping -w5 -c3 $host2) > /dev/null 2>&1) && echo "up" || (echo "down" && exit 1) How would you do it? Which hosts would you ping? Thanks in advance.

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• Has ordinal index of functions in Windows API dlls ever changed?

  - by Panda

  You know that functions in a dll can be imported either by name or by ordinal index. From wikipedia: For most Windows API functions only the names are preserved across different Windows releases; the ordinals are subject to change. Thus, one cannot reliably import Windows API functions by their ordinals. My Question: I know these ordinals MAY CHANGE, but I want to know if they've ever ACTUALLY CHANGED. (Especially about kernel32 & user32 dlls) Why I'm asking this? I heard some viruses do import win32 functions by ordinal. I want to catch them, and I want to know whether I can test for an ordinal number or not. Thanks.

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• Why does Perl lose foreign characters on Windows input - can this be fixed (if so, how) or is Perl an outdated dinosaur that just can't handle this?

  - by Alex R

  Note below how ã changes to a This is causing me a huge problem as foreign characters show up in URLs, e.g. http://pt.wikipedia.org/wiki/Cão The OS is Windows 7, 64-bit. The Perl is: This is perl 5, version 12, subversion 2 (v5.12.2) built for MSWin32-x64-multi-thread (with 8 registered patches, see perl -V for more detail) Copyright 1987-2010, Larry Wall Binary build 1202 [293621] provided by ActiveState http://www.ActiveState.com Built Sep 6 2010 22:53:42 Additional update: To get around my particular problem, I tried using File::Find instead of piped input. The issue actually gets worse:

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• What open source document-oriented database system is most mature for Windows usage?

  - by jdk

  After using relational databases as back-end storage all my Windows programming life (currently .NET), I want to experiment with a document-oriented database by this Wikipedia definition; it can be standalone or layered over an existing non-commercial database system. What open source document-oriented database solution would you recommend from your own experience and why? A nice to have would be a .NET provider. Admittedly this is somewhat subjective and potentially argumentative so keep it real folks and I'll do the same - also your answers will be invaluable to others looking into document-oriented databases for the first time on Windows. I'm sure the overall value of your answers will outweigh any biases. Thanks.

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• Use CSS selectors to collect HTML elements from a streaming parser (e.g. SAX stream)

  - by Jakub Narebski

  How to parse CSS (CSS3) selector and use it (in jQuery-like way) to collect HTML elements not from DOM (from tree structure), but from stream (e.g. SAX), i.e. using sequential access parser? Are there CSS selectors that need access to DOM (Wikipedia SAX page says that XPath selectors "need to be able to access any node at any time in the parsed XML tree")? I am most inetersted in implementing selector combinators, e.g. 'A B' descendant selector. I prefer solutions describing algorithm, or in Perl.

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• command design pattern usage

  - by sagie

  Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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• help implementing All Nearest Smaller Values algorithm

  - by davit-datuashvili

  http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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• Library for Dataflow in C

  - by msutherl

  How can I do dataflow (pipes and filters, stream processing, flow based) in C? And not with UNIX pipes. I recently came across stream.py. Streams are iterables with a pipelining mechanism to enable data-flow programming and easy parallelization. The idea is to take the output of a function that turns an iterable into another iterable and plug that as the input of another such function. While you can already do this using function composition, this package provides an elegant notation for it by overloading the operator. I would like to duplicate a simple version of this kind of functionality in C. I particularly like the overloading of the operator to avoid function composition mess. Wikipedia points to this hint from a Usenet post in 1990. Why C? Because I would like to be able to do this on microcontrollers and in C extensions for other high level languages (Max, Pd*, Python). * (ironic given that Max and Pd were written, in C, specifically for this purpose – I'm looking for something barebones)

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• commad design pattern usage

  - by sagie

  Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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