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• How do I get Nunit to run selenium tests against different servers?

  - by Jon

  I have an Nunit test which uses selenium RC to run tests against our UI. I want to run the tests against 2 different servers, which means having the call to selenium.open() with 2 different servers. However, I don't want to have 2 different Nunit test suites that do the same thing but against different servers. I need a way of passing parameters from Nant or the Nunit driver program to specific which server to test against. Is there anyway to do this?

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• How can I programmatically determine (in Python) when someone connects into my windows 7 machine via

  - by Jon Cage

  This doesn't need to be a real time solution, but are there some log files or system messages that could be read to identify periods of time where someone was connected via RDP to a Windows 7 machine? I'm building a watchdog script for a computer which will be deployed in a remote place and would like to add this metric to a daily status update.

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• how to dynamically (re)position an element according to the bottom of the page using JS / Jquery?

  - by jon

  Hi All, the back story: i have a tab section on a page which when navigated through displays sections (divs) of varying height. the result, is that certain inputs (which are strangely positioned for reasons i can't change) on this page reposition themselves problematically. the proposed solution: as the page height changes, have these problem inputs repositioned according to the page bottom (from which their appropriate distances are always a constant). what i'm thinking is that i need some js that does something like, page height change triggers input position from bottom to = x. there are two inputs if that's at all relevant. :) if only there was css for this (i know there is under normal circumstances, but trust me -- not in this case). thanks for your time & help i've been struggling with this for weeks!

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• How to determine which enemy is hit and destroy it alone

  - by Jon Ferriter

  http://jsfiddle.net/5DB6K/ I have this game being made where you shoot enemies from the sides of the screen. I've got the bullets moving and being removed when they reach the end of the screen (if they didn't hit any enemy) and removing the enemy when they collide with it. //------------collision----------------// if(shot === true){ bulletY = $('.bullet').position().top + 2; bulletX = $('.bullet').position().left + 2; $('.enemy').each(function(){ if($('.enemy').hasClass('smallEnemy')){ enemyY = $(this).position().top + 7; enemyX = $(this).position().left + 7; if(Math.abs(bulletY - enemyY) <= 9 && Math.abs(bulletX - enemyX) <=9){ $(this).remove(); score = score + 40; bulletDestroy(); } } }); } However, the bullet destroys every enemy if the collision check is right which isn't what I want. I want to check if the enemy has the class of either smallEnemy, medEnemy, or lrgEnemy and then do the collision check which is what I thought I had but it doesn't seem to work. Also, the game starts to lag the more and more time goes on. Would anyone know the reason for that?

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• Find where a variable is defined in PHP (And/or SMARTY)?

  - by Jon

  I'm currently working on a very large project, and am under a lot of pressure to finish it soon, and I'm having a serious problem. The programmer who wrote this last defined variables in a very odd way - the config variables aren't all in the same file, they're spread out across the entire project of over 500 files and 100k+ lines of code, and I'm having a hell of a time figuring out where a certain variable is, so I can fix an issue. Is there a way to track this variable down? I believe he's using SMARTY (Which I can not stand, due to issues like this), and the variable is a template variable. I'm fairly sure that the variable I'm looking for was initially defined as a PHP variable, then that variable is passed into SMARTY, so I'd like to track down the PHP one, however if that's impossible - how can I track down where he defined the variable for SMARTY? P.S. I'm in Vista, and don't have ssh access to the server, so 'grep' is out of the question.

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• Output Caching - why doesn't it seem to do the job?

  - by Jon

  Hi, I have quite a big user control which creates an ASP.NET tab menu and within each tab a lengthy set of icons/menus. The menu is dynamically created from the database. I thought I could wrap the user control with an output cache directive to speed things up. I set OutputCache varybyparam="none" and duration to 120 seconds. When I navigate to my page, the usercontrol containing the tab menus and icons etc just vanishes? I thought ASP.NET was supposed to deliver some HTML that would previously have been cached. So why isn't this working? It doesn't seem to do what the label says on the tin?!? ;)

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• Text extra aliased(jagged) in IE - looks terrible - but OK in FF and Chrome

  - by jon

  I am building a website - http://www.efficaxdevelopment.com As you can see when you load the page(in IE) the text on the page that isn't an image or the menu looks terrible, while in FF and Chrome the text looks fine. you can view the source on the page and the css is here http://www.efficaxdevelopment.com/styles/mainstyle.css Also, the sliding bar over the menu appears a few pixels left of where it appears in FF and IE. Any ideas?

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• Weird output as the numbers get bigger in Fibonacci sequence

  - by Jon

  I noticed in my fibonacci sequence that I'm getting negative numbers after a certain point. Does this have to do with the limited range of "int"? or is there something wrong with my code? Here is the code: using std::cout; int main() { int n = 50, f1 = 0, f2 = 1, fn = 0, i = 0; cout << "0 "; for (i = 0; i < n; i++) { fn = f1 + f2; f2 = f1; f1 = fn; cout << fn << " "; }

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• Orchestrating the Virtual Enterprise, Part II

  - by Kathryn Perry

  A guest post by Jon Chorley, Oracle's CSO & Vice President, SCM Product Strategy Almost everyone has ordered from Amazon.com at one time or another. Our orders are as likely to be fulfilled by third parties as they are by Amazon itself. To deliver the order promptly and efficiently, Amazon has to send it to the right fulfillment location and know the availability in that location. It needs to be able to track status of the fulfillment and deal with exceptions. As a virtual enterprise, Amazon's operations, using thousands of trading partners, requires a very different approach to fulfillment than the traditional 'take an order and ship it from your own warehouse' model. Amazon had no choice but to develop a complex, expensive and custom solution to tackle this problem as there used to be no product solution available. Now, other companies who want to follow similar models have a better off-the-shelf choice -- Oracle Distributed Order Orchestration (DOO).  Consider how another of our customers is using our distributed orchestration solution. This major airplane manufacturer has a highly complex business and interacts regularly with the U.S. Government and major airlines. It sits in the middle of an intricate supply chain and needed to improve visibility across its many different entities. Oracle Fusion DOO gives the company an orchestration mechanism so it could improve quality, speed, flexibility, and consistency without requiring an organ transplant of these highly complex legacy systems. Many retailers face the challenge of dealing with brick and mortar, Web, and reseller channels. They all need to be knitted together into a virtual enterprise experience that is consistent for their customers. When a large U.K. grocer with a strong brick and mortar retail operation added an online business, they turned to Oracle Fusion DOO to bring these entities together. Disturbing the Peace with Acquisitions Quite often a company's ERP system is disrupted when it acquires a new company. An acquisition can inject a new set of processes and systems -- or even introduce an entirely new business like Sun's hardware did at Oracle. This challenge has been a driver for some of our DOO customers. A large power management company is using Oracle Fusion DOO to provide the flexibility to rapidly integrate additional products and services into its central fulfillment operation. The Flip Side of Fulfillment Meanwhile, we haven't ignored similar challenges on the supply side of the equation. Specifically, how to manage complex supply in a flexible way when there are multiple trading parties involved? How to manage the supply to suppliers? How to manage critical components that need to merge in a tier two or tier three supply chain? By investing in supply orchestration solutions for the virtual enterprise, we plan to give users better visibility into their network of suppliers to help them drive down costs. We also think this technology and full orchestration process can be applied to the financial side of organizations. An example is transactions that flow through complex internal structures to minimize tax exposure. We can help companies manage those transactions effectively by thinking about the internal organization as a virtual enterprise and bringing the same solution set to this internal challenge.  The Clear Front Runner No other company is investing in solving the virtual enterprise supply chain issues like Oracle is. Oracle is in a unique position to become the gold standard in this market space. We have the infrastructure of Oracle technology. We already have an Oracle Fusion DOO application which embraces the best of what's required in this area. And we're absolutely committed to extending our Fusion solution to other use cases and delivering even more business value. Jon ChorleyChief Sustainability Officer & Vice President, SCM Product StrategyOracle Corporation

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• C# internal VS VBNET Friend

  - by Will Marcouiller

  To this SO question: What is the C# equivalent of friend?, I would personally have answered "internal", just like Ja did among the answers! However, Jon Skeet says that there is no direct equivalence of VB Friend in C#. If Jon Skeet says so, I won't be the one telling otherwise! ;P I'm wondering how can the keyword internal (C#) not be the equivalent of Friend (VBNET) when their respective definitions are: Friend VBNET The Friend (Visual Basic) keyword in the declaration statement specifies that the elements can be accessed from within the same assembly, but not from outside the assembly. [...] internal C# Internal: Access is limited to the current assembly. To my understanding, these definitions mean quite the same to me. Then, respectively, when I'm coding in VB.NET, I use the Friend keyword to specify that a class or a property shall be accessible only within the assembly where it is declared. The same in C#, I use the internal keyword to specify the same. Am I doing something or anything wrong from this perspective? What are the refinements I don't get? Might someone please explain how or in what Friend and internal are not direct equivalences? Thanks in advance for any of your answers!

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• What is the difference between these two linq implementations?

  - by Mahesh Velaga

  I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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• One-to-many Associations Empty Columns Issue (Ext on Rails)

  - by Joe

  I'm playing with rewriting part of a web application in Rails + Ext. However, I'm having trouble getting an associated models' name to display in the grid view. I've been able to successfully convert several models and arrange the views nicely using tabs and Ext's layout helpers. However, I'm in the middle of setting up an association -- I've followed along with Jon Barket's tutorial on how to do this using Ext -- and I've made all the Rails and JS changes suggested (with appropriate name changes for my models,) the result being that the combo box is now being correctly populated with the names of the associated models, and changes are actually written correctly to database, BUT the data doesn't show up in the column, it's just empty. However, the correct data is there in the 'detail' view. Really just wondering if anyone else ran into this, or had any thoughts on what could be happening. Definitely willing to post code if requested; just note that (AFAIK) my changes follow the tutorial pretty closely. Thanks in advance! UPDATE: Alright, slight progress - kind of. I can get the associated model id # displaying properly -- just by modifying the column model slightly. But I can't get the virtual attribute displayed in the main table (in Jon's example it's country_name.) It still goes blank when I change the data source for that column from dataIndex: 'model[associated_model_id]' to dataIndex: 'virtual_attributes[associated_model_name]' ANOTHER UPDATE: Bump. Has NOBODY here tried integrating Ext with Rails?

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• Error when starting ArcGIS Server Object Manager (v10)

  - by SpatialBridge

  I just finished installing ArcGIS Server 10 and completed the post-installation. The ArcGIS Server Object Manager service is installed, but when I try to start it, I get the following error: "Windows could not start the ArcGIS Server Object Manager service on the Local Computer. Error 1067: The process terminated unexpectedly." The agsadmin and agsusers groups exist, and my local account is a member of the agsadmin group. Any ideas on what I've done wrong? Thanks, Jon.

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• Syslog message '^@' indicates server crash

  - by user1456214

  The php-cgi's died on a vps I look after and the only syslog entry is this followed by me restarting the VM: ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@ ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@Jun 13 22:00:34 VM syslogd 1.5.0#5ubuntu4: restart. Everything before appears to be fine, and there's nothing in the php log even though php timing out was the most obvious symptom (nginx was returning 504s), any ideas how to debug this? Thanks, Jon

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• How safe am I singing into Google Spreadsheets with yeroon.net/ggplot2

  - by Farrel

  I am impressed by what I have seen of yeroon.net/ggplot2 which is a web interface for Hadley Wickham's R package ggplot2. I want to try it out on my own data. The part that has me very excited is that one can use data stored in one's own Google spreadsheet as the data. One just signs into their Google Account so that yeroon.net/ggplot2 can access the spreadsheet list. I have been hesitant to do it. If I sign in whilst on yeroon.net am I handing over my username and password to a third party? It would not be wise of me to divulge my google password to third parties since Google is fast becoming my repository of everything. How do I know if Jeroon's application is using ClientLogin or OAuth? My understanding is very basic and may be wrong but nevertheless here it is. OAuth would be better since it does not actually pass the password onto the third party application.

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• How safe am I signing into Google Spreadsheets with yeroon.net/ggplot2

  - by Farrel

  I am impressed by what I have seen of yeroon.net/ggplot2 which is a web interface for Hadley Wickham's R package ggplot2. I want to try it out on my own data. The part that has me very excited is that one can use data stored in one's own Google spreadsheet as the data. One just signs into their Google Account so that yeroon.net/ggplot2 can access the spreadsheet list. I have been hesitant to do it. If I sign in whilst on yeroon.net am I handing over my username and password to a third party? It would not be wise of me to divulge my google password to third parties since Google is fast becoming my repository of everything. How do I know if Jeroon's application is using ClientLogin or OAuth? My understanding is very basic and may be wrong but nevertheless here it is. OAuth would be better since it does not actually pass the password onto the third party application.

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• break dataframe into subsets by factor values, send to function that returns glm class, how to recom

  - by Alex Holcombe

  Thanks to Hadley's plyr package ddply function we can take a dataframe, break it down into subdataframes by factors, send each to a function, and then combine the function results for each subdataframe into a new dataframe. But what if the function returns an object of a class like glm or in my case, a c("glm", "lm"). Then, these can't be combined into a dataframe can they? I get this error instead Error in as.data.frame.default(x[[i]], optional = TRUE, stringsAsFactors = stringsAsFactors) : cannot coerce class 'c("glm", "lm")' into a data.frame Is there some more flexible data structure that will accommodate all the complex glm class results of my function calls, preserving the information regarding the dataframe subsets? Or should this be done in an entirely different way?

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• How can I manipulate the strip text of facet plots in ggplot2?

  - by briandk

  I'm wondering how I can manipulate the size of strip text in facetted plots. My question is similar to a question on plot titles, but I'm specifically concerned with manipulating not the plot title but the text that appears in facet titles (strip_h). As an example, consider the mpg dataset. library(ggplot2) qplot(hwy, cty, data = mpg) + facet_grid( . ~ manufacturer) The resulting output produces some facet titles that don't fit in the strip. I'm thinking there must be a way to use grid to deal with the strip text. But I'm still a novice and wasn't sure from the grid appendix in Hadley's book how, precisely, to do it. Also, I was afraid if I did it wrong it would break my washing machine, since I believe all technology is connected through The Force :-( Many thanks in advance.

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• Extract a regular expression match in R version 2.10

  - by tovare

  Hi, I'm trying to extract a number from a string. And do something like this [0-9]+ on this string "aaaa12xxxx" and get "12". I thought it would be something like: > grep("[0-9]+","aaa12xxx", value=TRUE) [1] "aaa12xxx" And then I figured... > sub("[0-9]+", "\\1", "aaa12xxxx") [1] "aaa12xxx" But I got some form of response doing: > sub("[0-9]+", "ARGH!", "aaa12xxxx") [1] "aaaARGH!xxx" There's a small detail I'm missing Please advice :-) I'm using R version 2.10.1 (2009-12-14) Thanks ! Comments on the solution The best solution is to ignore the standard functions and install Hadley Wickham's stringr package to get something that actually makes sense. Kudos to Marek for figuring out how the standard library worked.

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• Using reshape + cast to aggregate over multiple columns

  - by DamonJW

  In R, I have a data frame with columns for Seat (factor), Party (factor) and Votes (numeric). I want to create a summary data frame with columns for Seat, Winning party, and Vote share. For example, from the data frame df <- data.frame(party=rep(c('Lab','C','LD'),times=4), votes=c(1,12,2,11,3,10,4,9,5,8,6,15), seat=rep(c('A','B','C','D'),each=3)) I want to get the output seat winner voteshare 1 A C 0.8000000 2 B Lab 0.4583333 3 C C 0.5000000 4 D LD 0.5172414 I can figure out how to achieve this. But I'm sure there must be a better way, probably a cunning one-liner using Hadley Wickham's reshape package. Any suggestions? For what it's worth, my solution uses a function from my package djwutils_2.10.zip and is invoked as follows. But there are all sorts of special cases it doesn't deal with, so I'd rather rely on someone else's code. aggregateList(df, by=list(seat=seat), FUN=list(winner=function(x) x$party[which.max(x$votes)], voteshare=function(x) max(x$votes)/sum(x$votes)))

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• Megjelent a MySQL 5.5

  - by Lajos Sárecz

  Rekord ido alatt készült el az új MySQL 5.5 verziót, melyet a mai nap jelentett be az Oracle. Ez újabb bizonyítéka annak, hogy az Oracle komolyan fejleszti a MySQL-t is, és igyekszik innovatív megoldásokkal megörvendeztetni a MySQL felhasználókat is. Akinek 'Déja-vu' érzése van, az nem véletlen, hiszen a szeptemberi OpenWorld konferencián került bejelentésre a MySQL 5.5 RC, azaz a Release Candidate, melyrol beszámolt például a hwsw.hu is. Az új verzióban elsosorban a teljesítményen és a skálázhatóságon fejlesztett az Oracle. Így például alapértelmezetten az InnoDB storage engine jön a MySQL-el, aminek köszönhetoen például ACID (atomicity, consistency, isolation, durability) tranzakciókat hajt végre az adatbázis-kezelo (ez mondjuk nem egy apró részlet...). Emellett újdonságot jelent még a majdnem szinkron replikáció, a fejlettebb index és tábla particionálás, valamint diagnosztika terén bevezetésre került egy új PERFORMANCE_SCHEMA, aminek köszönhetoen javult a MySQL menedzselhetosége. A RC verzióval futtatott tesztek jelentos gyorsulást mutattak a MySQL 5.1-es verziójához képest, így érdemes megfontolni a verzió frissítést.

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• Pure virtual or abstract, what's in a name?

  - by Steven Jeuris

  While discussing a question about virtual functions on Stack Overflow, I wondered whether there was any official naming for pure (abstract) and non-pure virtual functions. I always relied on wikipedia for my information, which states that pure and non-pure virtual functions are the general term. Unfortunately, the article doesn't back it up with a origin or references. To quote Jon Skeet's answer to my reply that pure and non-pure are the general term used: @Steven: Hmm... possibly, but I've only ever seen it in the context of C++ before. I suspect anyone talking about them is likely to have a C++ background :) Did the terms originate from C++, or were they first defined or implemented in a earlier language, and are they the 'official' scientific terms?

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• Programming Pearls (2nd Edition) vs More Programming Pearls: Confessions of a Coder [closed]

  - by Geek

  I have been reading very good reviews of the books by Jon Bentley : Programming Pearls (2nd Edition) More Programming Pearls: Confessions of a Coder. I know that these books have been out there for a long time and I feel bad that I haven't read either one . But it is always better late than never . I understand that the second one was written after the first one . So are these two books complementary to each other ? Do the second one assume that the reader has read the first one ? For some one who haven't read either which one would you propose to read up first ?

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• F# for the C# Programmer

  - by mbcrump

  Are you a C# Programmer and can’t make it past a day without seeing or hearing someone mention F#?  Today, I’m going to walk you through your first F# application and give you a brief introduction to the language. Sit back this will only take about 20 minutes. Introduction Microsoft's F# programming language is a functional language for the .NET framework that was originally developed at Microsoft Research Cambridge by Don Syme. In October 2007, the senior vice president of the developer division at Microsoft announced that F# was being officially productized to become a fully supported .NET language and professional developers were hired to create a team of around ten people to build the product version. In September 2008, Microsoft released the first Community Technology Preview (CTP), an official beta release, of the F# distribution . In December 2008, Microsoft announced that the success of this CTP had encouraged them to escalate F# and it is now will now be shipped as one of the core languages in Visual Studio 2010 , alongside C++, C# 4.0 and VB. The F# programming language incorporates many state-of-the-art features from programming language research and ossifies them in an industrial strength implementation that promises to revolutionize interactive, parallel and concurrent programming. Advantages of F# F# is the world's first language to combine all of the following features: Type inference: types are inferred by the compiler and generic definitions are created automatically. Algebraic data types: a succinct way to represent trees. Pattern matching: a comprehensible and efficient way to dissect data structures. Active patterns: pattern matching over foreign data structures. Interactive sessions: as easy to use as Python and Mathematica. High performance JIT compilation to native code: as fast as C#. Rich data structures: lists and arrays built into the language with syntactic support. Functional programming: first-class functions and tail calls. Expressive static type system: finds bugs during compilation and provides machine-verified documentation. Sequence expressions: interrogate huge data sets efficiently. Asynchronous workflows: syntactic support for monadic style concurrent programming with cancellations. Industrial-strength IDE support: multithreaded debugging, and graphical throwback of inferred types and documentation. Commerce friendly design and a viable commercial market. Lets try a short program in C# then F# to understand the differences. Using C#: Create a variable and output the value to the console window: Sample Program. using System;   namespace ConsoleApplication9 {     class Program     {         static void Main(string[] args)         {             var a = 2;             Console.WriteLine(a);             Console.ReadLine();         }     } } A breeze right? 14 Lines of code. We could have condensed it a bit by removing the “using” statment and tossing the namespace. But this is the typical C# program. Using F#: Create a variable and output the value to the console window: To start, open Visual Studio 2010 or Visual Studio 2008. Note: If using VS2008, then please download the SDK first before getting started. If you are using VS2010 then you are already setup and ready to go. So, click File-> New Project –> Other Languages –> Visual F# –> Windows –> F# Application. You will get the screen below. Go ahead and enter a name and click OK. Now, you will notice that the Solution Explorer contains the following: Double click the Program.fs and enter the following information. Hit F5 and it should run successfully. Sample Program. open System let a = 2        Console.WriteLine a As Shown below: Hmm, what? F# did the same thing in 3 lines of code. Show me the interactive evaluation that I keep hearing about. The F# development environment for Visual Studio 2010 provides two different modes of execution for F# code: Batch compilation to a .NET executable or DLL. (This was accomplished above). Interactive evaluation. (Demo is below) The interactive session provides a > prompt, requires a double semicolon ;; identifier at the end of a code snippet to force evaluation, and returns the names (if any) and types of resulting definitions and values. To access the F# prompt, in VS2010 Goto View –> Other Window then F# Interactive. Once you have the interactive window type in the following expression: 2+3;; as shown in the screenshot below: I hope this guide helps you get started with the language, please check out the following books for further information. F# Books for further reading   Foundations of F# Author: Robert Pickering An introduction to functional programming with F#. Including many samples, this book walks through the features of the F# language and libraries, and covers many of the .NET Framework features which can be leveraged with F#.       Functional Programming for the Real World: With Examples in F# and C# Authors: Tomas Petricek and Jon Skeet An introduction to functional programming for existing C# developers written by Tomas Petricek and Jon Skeet. This book explains the core principles using both C# and F#, shows how to use functional ideas when designing .NET applications and presents practical examples such as design of domain specific language, development of multi-core applications and programming of reactive applications.

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• Why do you need float/double?

  - by acidzombie24

  I was watching http://www.joelonsoftware.com/items/2011/06/27.html and laughed at Jon Skeet joke about 0.3 not being 0.3. I personally never had problems with floats/decimals/doubles but then I remember I learned 6502 very early and never needed floats in most of my programs. The only time I used it was for graphics and math where inaccurate numbers were ok and the output was for the screen and not to be stored (in a db, file) or dependent on. My question is, where are places were you typically use floats/decimals/double? So I know to watch out for these gotchas. With money I use longs and store values by the cent, for speed of an object in a game I add ints and divide (or bitshift) the value to know if I need to move a pixel or not. (I made object move in the 6502 days, we had no divide nor floats but had shifts). So I was mostly curious.

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