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• Where and how to start on C# and .Net Framework ?

  - by Rachel

  Currently, I have been working as an PHP developer for approximately 1 year now and I want learn about C# and .Net Framework, I do not have any experience with .Net Framework and C# and also there is not firm basis as to why I am going for C# and .Net Framework vs Java or any other programming languages, this decision is mere on career point of view and job opportunities. So my question is about: Is my decision wise to go for C# and .Net Framework route after working for sometime as an PHP Developer ? What are the good resources which I can refer and learn from to get knowledge on C# and .NET Framework ? How should I go about learning on C# and .NET Framework ? What all technologies should I be learning OR have experience with to be considered as an C#/.Net Developer, I am mentioning some technologies, please add or suggest one, if am missing out any ? Technologies C#-THE LANGUAGE GUI APPLICATION DEVELOPMENT WINDOWS CONTROL LIBRARY DELEGATES DATA ACCESS WITH ADO.NET MULTI THREADING ASSEMBLIES WINDOWS SERVICES VB INTRODUCTION TO VISUAL STUDIO .NET WINDOWS CONTROL LIBRARY DATA ACCESS WITH ADO.NET ASP.NET WEB TECHNOLOGIES CONTROLS VALIDATION CONTROL STATE MANAGEMENT CACHING ASP.NET CONFIGURATION ADO.NET ASP.NET TRACING & SECURITY IN ASP.NET XMLPROGRAMMING WEB SERVICES CRYSTAL REPORTS SSRS (SQL Server Reporting Services) MS-Reports LINQ: NET Language-Integrated Query NET Language-Integrated Query LINQ to SQL: SQL Integration WCF: Windows Communication Foundation What Is Windows Communication Foundation? Fundamental Windows Communication Foundation Concepts Windows Communication Foundation Architecture WPF: Windows Presentation Foundation Getting Started (WPF) Application Development WPF Fundamentals What are your thoughts, suggestions on this and from Job and Market Perspective, what areas of C#/.Net Development should I put my focus on ? I know this is very subjective and long question but advice would be highly appeciated. Thanks.

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• Need some ignition for learning Embedded Systems

  - by Rahul

  I'm very much interested in building applications for Embedded Devices. I'm in my 3rd year Electrical Engineering and I'm passionate about coding, algorithms, Linux OS, etc. And also by Googling I found out that Linux OS is one of the best OSes for Embedded devices(may be/may not be). I want to work for companies which work on mobile applications. I'm a newbie/naive to this domain & my skills include C/C++ & MySQL. I need help to get started in the domain of Embedded Systems; like how/where to start off, Hardware prerequisites, necessary programming skills, also what kind of Embedded Applications etc. I've heard of ARM, firmware, PIC Micorcontrollers; but I don't know anything & just need proper introduction about them. Thanx. P.S: I'm currently reading Bjarne Struotsup's lecture in C++ at Texas A&M University, and one chapter in it describes about Embedded Systems Programming.

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• git doesn't show where code was removed.

  - by Andrew Myers

  So I was tasked at replacing some dummy code that our project requires for historical compatibility reasons but has mysteriously dropped out sometime since the last release. Since disappearing code makes me nervous about what else might have gone missing but un-noticed I've been digging through the logs trying to find in what commit this handful of lines was removed. I've tried a number of things including "git log -S'add-visit-resource-pcf'", git blame, and even git bisect with a script that simply checks for the existence of the line but have been unable to pinpoint exactly where these lines were removed. I find this very perplexing, particularly since the last log entry (obtained by the above command) before my re-introduction of this code was someone else adding the code as well. commit 0b0556fa87ff80d0ffcc2b451cca1581289bbc3c Author: Andrew Date: Thu May 13 10:55:32 2010 -0400 Re-introduced add-visit-resource-pcf, see PR-65034. diff --git a/spike/hst/scheduler/defpackage.lisp b/spike/hst/scheduler/defpackage.lisp index f8e692d..a6f8d38 100644 --- a/spike/hst/scheduler/defpackage.lisp +++ b/spike/hst/scheduler/defpackage.lisp @@ -115,6 +115,7 @@ #:add-to-current-resource-pcf #:add-user-package-nickname #:add-value-criteria + #:add-visit-resource-pcf #:add-window-to-gs-params #:adjust-derived-resources #:adjust-links-candidate-criteria-types commit 9fb10e25572c537076284a248be1fbf757c1a6e1 Author: Bob Date: Sun Jan 17 18:35:16 2010 -0500 update-defpackage for Spike 33.1 Delivery diff --git a/spike/hst/scheduler/defpackage.lisp b/spike/hst/scheduler/defpackage.lisp index 983666d..47f1a9a 100644 --- a/spike/hst/scheduler/defpackage.lisp +++ b/spike/hst/scheduler/defpackage.lisp @@ -118,6 +118,7 @@ #:add-user-package-nickname #:add-value-criteria #:add-vars-from-proposal + #:add-visit-resource-pcf #:add-window-to-gs-params #:adjust-derived-resources #:adjust-links-candidate-criteria-types This is for one of our package definition files, but the relevant source file reflects something similar. Does anyone know what could be going on here and how I could find the information I want? It's not really that important but this kind of things makes me a bit nervous.

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• Generate a table of contents from HTML with Python

  - by Oli

  I'm trying to generate a table of contents from a block of HTML (not a complete file - just content) based on its <h2> and <h3> tags. My plan so far was to: Extract a list of headers using beautifulsoup Use a regex on the content to place anchor links before/inside the header tags (so the user can click on the table of contents) -- There might be a method for replacing inside beautifulsoup? Output a nested list of links to the headers in a predefined spot. It sounds easy when I say it like that, but it's proving to be a bit of a pain in the rear. Is there something out there that does all this for me in one go so I don't waste the next couple of hours reinventing the wheel? A example: <p>This is an introduction</p> <h2>This is a sub-header</h2> <p>...</p> <h3>This is a sub-sub-header</h3> <p>...</p> <h2>This is a sub-header</h2> <p>...</p>

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• Does Perl auto-vivify variables used as references in subroutine calls?

  - by FM

  I've declared 2010 to be the year of higher-order programming, so I'm learning Haskell. The introduction has a slick quick-sort demo, and I thought, "Hey, that's easy to do in Perl". It turned to be easier than I expected. Note that I don't have to worry about whether my partitions ($less and $more) are defined. Normally you can't use an undefined value as an array reference. use strict; use warnings; use List::MoreUtils qw(part); my @data = (5,6,7,4,2,9,10,9,5,1); my @sorted = qsort(@data); print "@sorted\n"; sub qsort { return unless @_; my $pivot = shift @_; my ($less, $more) = part { $_ < $pivot ? 0 : 1 } @_; # Works, even though $less and $more are sometimes undefined. return qsort(@$less), $pivot, qsort(@$more); } As best I can tell, Perl will auto-vivify a variable that you try to use as a reference -- but only if you are passing it to a subroutine. For example, my call to foo() works, but not the attempted print. use Data::Dumper qw(Dumper); sub foo { print "Running foo(@_)\n" } my ($x); print Dumper($x); # Fatal: Can't use an undefined value as an ARRAY reference. # print @$x, "\n"; # But this works. foo(@$x); # Auto-vivification: $x is now []. print Dumper($x); My questions: Am I understanding this behavior correctly? What is the explanation or reasoning behind why Perl does this? Is this behavior explained anywhere in the docs?

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• Using ScriptingBridge framework for communicating with Entourage

  - by Subramanian Ganapathy

  Hi, The motivation for my question is the following doc, which describes how mail.app could be integrated using ScriptingBridge: http://developer.apple.com/mac/library/samplecode/SBSendEmail/Introduction/Intro.html I tried to apply a similar technique with Entourage as well but could not get any results so far. I understand that using AppleScript would help me solve my problem and mactech.com has extensive documentation for doing so. But i find this ScriptingBridge technique elegant and want to figure why it is not working for me with Entourage. The biggest problem seems to be my inability to create Scripting classes based on their names as it happens in Mail because Entourage has a different interface than Mail as their headers indicate. Could someone please tell me what I am missing or provide any sort of hint on why this wont work? I am also adding sample code ` MicrosoftEntourageApplication * mail = [SBApplication applicationWithBundleIdentifier:@"com.Microsoft.Entourage"]; MicrosoftEntourageOutgoingEmailMessage * emailMessage = [[[mail classForScriptingClass:@"outgoing message"] alloc] initWithProperties: [NSDictionary dictionaryWithObjectsAndKeys: @"my sample subject", @"subject", @"my sample body", @"content", nil]]; //then i create a set of recipients and try to use "to recipient" as the string scripting class id, but MicrosoftEntourageRecipient is returned as nil MicrosoftEntourageRecipient * theRecipient = [[[mail classForScriptingClass:@"to recipient"] alloc] initWithProperties: [NSDictionary dictionaryWithObjectsAndKeys: @"[email protected]", @"address", nil]]; ` I am trying to make the simple thing work, I am not even concentrating on the task I am supposed to do now. I am a Cocoa beginner( and willing to learn ), please excuse an syntactic naivetes and do point them out in the sample code, in addition to answering my question. Best Regards, Subramanian

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• how would you like computer science classes to be taught?

  - by aaa

  hello I am a graduate student now, and hopefully someday I will teach. my interests are C++, Python, embedded languages, and scientific computing. Meanwhile I daydream about how I would teach. I was not quite happy with my undergraduate university as I found many computer science classes lacking. so I would like to ask you, if you were a student, how would you like your computer science classes to be taught? I understand it is a very subjective question, but nevertheless I think it's important to know what people want. Some specific points I am interested in: should computer languages be taught explicitly, or should students be required to pick up language on their own? what is better for learning, tests, projects, some sort of take-home exam? how do you think classtime should be used? theory, introduction, explanations, etc.? do you think the group projects are important? how much about computer architecture do you want to learn in computer science class, not necessarily assembler class. should particular operating system/editor be mandated or encouraged? Thanks thank you for your comments. Question has been closed because it is a discussion question rather than Q&A. If you know appropriate website for discussions of such sort with low noise ratio, please let me know.

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• How to rename goals in Maven?

  - by mjs

  In the Maven document Introduction to the Build Lifecycle, a goal of display:time is described that outputs the current time. The plugin is as follows: ... <plugin> <groupId>com.mycompany.example</groupId> <artifactId>maven-touch-plugin</artifactId> <version>1.0</version> <executions> <execution> <phase>process-test-resources</phase> <goals> <goal>timestamp</goal> </goals> </execution> </executions> </plugin> ... I have several questions relating to this plugin: How can I change the name of the goal to, for example, foo:bar? (Why does neither display nor time appear anywhere in the XML fragment? How can you tell, from looking at the fragment, what goals it defines?) How can I manually run this goal? (For similar constructs, the equivalent of mvn display:time sometimes works, but this doesn't work consistently.) How can I see if this goal exists? (i.e. list available goals; this question suggests this is impossible.)

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• What techniques can be used to detect so called "black holes" (a spider trap) when creating a web crawler?

  - by Tom

  When creating a web crawler, you have to design somekind of system that gathers links and add them to a queue. Some, if not most, of these links will be dynamic, which appear to be different, but do not add any value as they are specifically created to fool crawlers. An example: We tell our crawler to crawl the domain evil.com by entering an initial lookup URL. Lets assume we let it crawl the front page initially, evil.com/index The returned HTML will contain several "unique" links: evil.com/somePageOne evil.com/somePageTwo evil.com/somePageThree The crawler will add these to the buffer of uncrawled URLs. When somePageOne is being crawled, the crawler receives more URLs: evil.com/someSubPageOne evil.com/someSubPageTwo These appear to be unique, and so they are. They are unique in the sense that the returned content is different from previous pages and that the URL is new to the crawler, however it appears that this is only because the developer has made a "loop trap" or "black hole". The crawler will add this new sub page, and the sub page will have another sub page, which will also be added. This process can go on infinitely. The content of each page is unique, but totally useless (it is randomly generated text, or text pulled from a random source). Our crawler will keep finding new pages, which we actually are not interested in. These loop traps are very difficult to find, and if your crawler does not have anything to prevent them in place, it will get stuck on a certain domain for infinity. My question is, what techniques can be used to detect so called black holes? One of the most common answers I have heard is the introduction of a limit on the amount of pages to be crawled. However, I cannot see how this can be a reliable technique when you do not know what kind of site is to be crawled. A legit site, like Wikipedia, can have hundreds of thousands of pages. Such limit could return a false positive for these kind of sites. Any feedback is appreciated. Thanks.

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• Delphi TRttiType.GetMethods return zero TRttiMethod instances

  - by conciliator

  I've recently been able to fetch a TRttiType for an interface using TRttiContext.FindType using Robert Loves "GetType"-workaround ("registering" the interface by an explicit call to ctx.GetType, e.g. RType := ctx.GetType(TypeInfo(IMyPrettyLittleInterface));). One logical next step would be to iterate the methods of said interface. Consider program rtti_sb_1; {$APPTYPE CONSOLE} uses SysUtils, Rtti, mynamespace in 'mynamespace.pas'; var ctx: TRttiContext; RType: TRttiType; Method: TRttiMethod; begin ctx := TRttiContext.Create; RType := ctx.GetType(TypeInfo(IMyPrettyLittleInterface)); if RType <> nil then begin for Method in RType.GetMethods do WriteLn(Method.Name); end; ReadLn; end. This time, my mynamespace.pas looks like this: IMyPrettyLittleInterface = interface ['{6F89487E-5BB7-42FC-A760-38DA2329E0C5}'] procedure SomeProcedure; end; Unfortunately, RType.GetMethods returns a zero-length TArray-instance. Are there anyone able to reproduce my troubles? (Note that in my example I've explicitly fetched the TRttiType using TRttiContext.GetType, not the workaround; the introduction is included to warn readers that there might be some unresolved issues regarding rtti and interfaces.) Thanks!

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• Need some ignition in Embedded Systems

  - by Rahul

  I'm very much interested in building applications for Embedded Devices. I'm in my 3rd year Electrical Engineering and I'm passionate about coding, algorithms, Linux OS, etc. And also by Googling I found out that Linux OS is one of the best OSes for Embedded devices(may be/may not be). I want to work for companies which work on mobile applications. I'm a newbie/naive to this domain & my skills include C/C++ & MySQL. I need help to get started in the domain of Embedded Systems; like how/where to start off, Hardware prerequisites, necessary programming skills, also what kind of Embedded Applications etc. I've heard of ARM, firmware, PIC Micorcontrollers; but I don't know anything & just need proper introduction about them. Thanx. P.S: I'm currently reading Bjarne Struotsup's lecture in C++ at Texas A&M University, and one chapter in it describes about Embedded Systems Programming.

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• When to choose which machine learning classifier?

  - by LM

  Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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• What is your favorite API developer community site? And why? [closed]

  - by whatupwilly

  There are a lot of great sites out there that offer good documentation, tools, tips, best-practices, sample code, etc. for the API's they are publishing. A sample: http://apiwiki.twitter.com http://developer.netflix.com/ http://developers.facebook.com/ https://affiliate-program.amazon.com/gp/advertising/api/detail/main.html http://code.google.com/ http://remix.bestbuy.com/ http://www.flickr.com/services/api/misc.overview.html http://products.wolframalpha.com/api/webserviceapi.html There are some no-brainers that I think a good developer site should have: Hi level introduction Quick start guide API specific details - showing example request and responses Links to sample code and/or 3rd party libraries Developer registration (e.g. get an API key) Blog But what about some other things: Online-Forum or Msg Board vs. Google Group (or similar) Galleries/ShowCases - spotlighting great apps built on the API - who has done nice galleries? Community Wiki - How do people feel about letting the community have edit rights on API documentation pages Online testing tools (like Facebook has a lot of nice interactive tools to simulate request/responses) What are some packages that you would recommend to put this all together: pbwiki Google Group pages MediaWiki API vendor package such as Sonoa Systems that offers a customizable developer portal So, to summarize: What are some other great API developer portals out there What are some nice features you like on them Any recommendations on what to use to build these features out Thanks, Will Zappos.com Public API (soon to launch) Product Manager

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• vectorizing loops in Matlab - performance issues

  - by Gacek

  This question is related to these two: http://stackoverflow.com/questions/2867901/introduction-to-vectorizing-in-matlab-any-good-tutorials http://stackoverflow.com/questions/2561617/filter-that-uses-elements-from-two-arrays-at-the-same-time Basing on the tutorials I read, I was trying to vectorize some procedure that takes really a lot of time. I've rewritten this: function B = bfltGray(A,w,sigma_r) dim = size(A); B = zeros(dim); for i = 1:dim(1) for j = 1:dim(2) % Extract local region. iMin = max(i-w,1); iMax = min(i+w,dim(1)); jMin = max(j-w,1); jMax = min(j+w,dim(2)); I = A(iMin:iMax,jMin:jMax); % Compute Gaussian intensity weights. F = exp(-0.5*(abs(I-A(i,j))/sigma_r).^2); B(i,j) = sum(F(:).*I(:))/sum(F(:)); end end into this: function B = rngVect(A, w, sigma) W = 2*w+1; I = padarray(A, [w,w],'symmetric'); I = im2col(I, [W,W]); H = exp(-0.5*(abs(I-repmat(A(:)', size(I,1),1))/sigma).^2); B = reshape(sum(H.*I,1)./sum(H,1), size(A, 1), []); But this version seems to be as slow as the first one, but in addition it uses a lot of memory and sometimes causes memory problems. I suppose I've made something wrong. Probably some logic mistake regarding vectorizing. Well, in fact I'm not surprised - this method creates really big matrices and probably the computations are proportionally longer. I have also tried to write it using nlfilter (similar to the second solution given by Jonas) but it seems to be hard since I use Matlab 6.5 (R13) (there are no sophisticated function handles available). So once again, I'm asking not for ready solution, but for some ideas that would help me to solve this in reasonable time. Maybe you will point me what I did wrong.

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• ARM Assembly - Converting Endianness

  - by SoulBeaver

  Hello people! This is currently a homework project that me and my teammate are stuck on. We haven't been given much of an introduction into Assembly, and this is supposed to be our first homework exercise. The task is to create a program that converts 0xAABBCCDD into 0xDDCCBBAA. I'm not looking for an answer, as that would defeat the purpose, but we are getting severely frustrated over the difficulty of this stupid thing. We think we have a good start in creating a viable solution, but we just cannot come up with the rest of the program. First, we mask every single tupel (aa), (bb), (cc), (dd) into a different register: LDR R0, LittleEndian // 0xAABBCCDD AND R1, R0, #0xFF000000 // 0xAA AND R2, R0, #0x00FF0000 // 0xBB AND R3, R0, #0x0000FF00 // 0xCC AND R4, R0, #0x000000FF // 0xDD Then we try to re-align them into the R0 register, but hell if we could come up with a good solution... Our best effort came from: ORR R0, R1, LSL #24 ORR R0, R2, LSL #8 ORR R0, R3, LSR #8 ORR R0, R4, LSR #24 which produced 0xBBBBCCDD for some odd reason; we really don't know. Any hints would be greatly appreciated. Again, we are asking for help, but not for a solution. Cheers!

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• Same font, character spacing and line-height but different results

  - by Ben Huh

  The introduction of @font-face in CSS3 allows web designers to use fonts that look the same across all browsers. That is what I thought until trying it out with the following code in jsFiddle: HTML: <div> The_Quick_Brown<br> Fox_Jumps_Over<br> The_Lazy_Dog </div> CSS: @font-face { font-family: 'Open Sans'; font-style: normal; font-weight: 400; src: url('http://themes.googleusercontent.com/static/fonts/opensans/v6/cJZKeOuBrn4kERxqtaUH3T8E0i7KZn-EPnyo3HZu7kw.woff') format('woff'); } div { display: block; width: 496px; height: 86px; font-size: 1.3em; font-family: 'Open Sans'; font-style: normal; margin: 0; border: 0; padding: 0; background: cyan; letter-spacing: 1.44em; line-height: 1.44; overflow: hidden; } This is the view from Firefox 12.0. Take note of the partially obscured 'o' in 'brown', the position of 'g' in 'dog' and the underscore '_' at the bottom edge. This is the view from Google Chrome 19.0. Despite explicitly setting letter-spacing and line-height for the same font, why are the results still different?

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• smlnj rephrased question for listdir(filename, directoryname)

  - by czy1985

  i am a newbie learning sml and the question i am thrown with involves IO functions that i have no idea how it works even after reading it. Here is the 2 questions that i really need help with to get me started, please provide me with codings and some explaination, i will be able to trial and error with the code given for the other questions. Q1) listdir(filename,directoryname), which given the name of a directory, list its contents in a text file. The listing is in a form that makes it easy to seperate filenames, dates and sizes from each other. (similar to what msdos does with "dir" but instead of just listing it out, it places all the files and details into a text file. Q2) readlist(filename) which reads a list of filenames (each of which were produced by listdir in (Q1) and combines them into one large list. (reads from the text file in Q1 and then assigning the contents into 1 big list containing all the information) Thing is, i only learned from the lecturer in school on the introduction section, there isnt even a system input or output example shown, not even the "use file" function is taught. if anyone that knows sml sees this, please help. Thanks to anyone who took the effort helping me. Thanks for the reply, current I am using SMLNJ to try and do this. Basically, Q1 requires me to list the directory's files of the "directoryname" provided into a text file in "filename". The Q2 requires me to read from the "filename" text file and then place the contents into one large list. Duplicate of: smlnj listdir

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• Is C++ (one of) the best language to learn at first

  - by AlexV

  C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's one that will reward in the long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Is C++ (one of) the best language to learn at first for you. Since it's subjective, I've marked this question as community wiki. EDIT: This question is not about why Java (or C# or any other language) is better than C++ to start with, it's about what's make C++ a good choice or not a good choice to learn as one of your firsts languages. For example, for me C++ made me understand how the memory works. Now today in many languages everything is managed by the garbadge collector and some people don't even know that. I'm glad I know how it works underneath and I think it can help you to write better code.

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• ADO.NET DataTable/DataRow Thread Safety

  - by Allen E. Scharfenberg

  Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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• C++ STL type_traits question.

  - by Kim Sun-wu

  I was watching the latest C9 lecture and noticed something interesting.. In his introduction to type_traits, Stephan uses the following (as he says, contrived) example: template <typename T> void foo(T t, true_type) { std::cout << t << " is integral"; } template <typename T> void foo(T t, false_type) { std::cout << t << " is not integral"; } template <typename T> void bar(T t) { foo(t, typename is_integral<T>::type()); } This seems to be far more complicated than: template <typename T> void foo(T t) { if(std::is_integral<T>::value) std::cout << "integral"; else std::cout << "not integral"; } Is there something wrong with the latter way of doing it? Is his way better? Why? Thanks.

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• Multiple exports with MEF does some really heinous stuff -- why, and why is it allowed?

  - by Dave

  I have an interesting situation where I need to do something like this: [Export[typeof(ICandy1)] [Export[typeof(ICandy2)] public class Candy : ICandy2 { ... } where public interface ICandy1 { ... } public interface ICandy2 : ICandy1 { ... } I couldn't find any posts anywhere regarding using multiple [Export] attributes, so I figured, what the hell, might as well try it. At first glance, it actually seemed to work. I have a couple of methods that call into both interfaces of a Candy instance, and it was fine. However, as I started to test the app, I saw that the behavior wasn't right, and when looking at the Output window, I saw that I was getting tons of COMExceptions. I couldn't track down where they were all coming from, but they always occurred when a worker thread was sleeping. I figured that it had to be from the main thread, then, but didn't know how to debug this at all. Nothing should have been going on in the GUI, and I disabled my DispatchTimers just in case -- same thing. Even more strange than the COMExceptions was the really, really erratic behavior when stepping through code. About 30% of the time, when I single stepped, it would pop out of the method, or it would single step over two lines of code! Totally weird stuff that I am not used to seeing. The only thing that changed between working and non-working code was the introduction of MEF through my plugin loading code. So as a test, I changed my plugin assembly to only export one interface, and I hardcoded everything in the app that relied on the other (now not-implemented) interface. And now the COMExceptions are gone, and the weird debugging behavior is gone. Is this something people here have seen before? If MEF is not expected to allow a class to Export multiple interfaces, then shouldn't a CompositionException get raised when composing the parts? Can anyone explain why MEF would cause these weird problems???

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• Using MATLAB's plotting features as an interactive part of a Fortran program

  - by ldigas

  Although many of you will have a decent idea of what I'm aiming at, just from reading the title -- allow me a simple introduction still. I have a Fortran program - it consists of a program, some internal subroutines, 7 modules with its own procedures, and ... uhmm, that's it. Without going into much detail, for I don't think it's necessary at this point, what would be the easiest way to use MATLAB's plotting features (mainly plot(x,y) with some customizations) as an interactive part of my program ? For now I'm using some of my own custom plotting routines (based on HPGL and Calcomp's routines), but just as part of an exercise on my part, I'd like to see where this could go and how would it work (is it even possible what I'm suggesting?). Also, how much effort would it take on my part ? I know this subject has been rather extensively described in many "tutorials" on the net, but for some reason I have trouble finding the really simple yet illustrative introductory ones. So if anyone can post an example or two, simple ones, I'd be really grateful. Or just take me by the hand and guide me through one working example. platform: IVF 11.something :) on Win XP SP2, Matlab 2008b

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• How can I create photo effects in Android?

  - by PaulH

  I'd like to make an Android app that lets a user apply cool effects to photos taken with the camera. There are already a few out there, I know, but I'd like to try my own hand at one. I'm trying to figure out the best way to implement these effects. Here are some examples from the excellent Vignette app (which I own): http://www.flickr.com/groups/vignetteforandroid/pool/ I have been googling and stack-overflowing, but so far I've mostly found some references to published papers or books. I am ordering this one from Amazon presently - Digital Image Processing: An Algorithmic Introduction using Java After some reading, I think I have a basic understanding of manipulating the RGB values for all the pixels in the image. My main question is how do I come up with a transformation that produces cool effects? By cool effects I mean some like those in the Vignette app or IPhone apps: ToyCamera Polarize I already have quite a bit of experience with Java, and I've made my first app for android already. Any ideas? Thanks in advance.

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• How do I implement a group of strings that starts randomly, but is bound by relevance upon selection?

  - by Freakishly

  Okay the title may be a little confusing, but here's what I'm trying to do :) I have a game in XNA where every tap from the user draws a moving circle on the screen. The circle has a tag, say 'dogs' displayed on it. So imagine multiple taps on the screen, and we have all these circles of various colors and sizes moving around the screen with different (but constant) velocities. Each circle with different tags: 'dogs', 'cats' and so on... Clicking on empty space generates a new circle at that point. Clicking on one of the circles "selects" it, turning it into a greeen shade and slowing its velocity down to a fraction of what it was. Clicking on it again "unselects" it, and restores its original color and velocity (trajectory does not change). With each circle comes a tag, and as of now I'm populating these tags randomly from a string array (which means there's a chance tags will repeat). I would like the tags for newly created circles to be relevant to previous "selected" tags. So when I click on 'dogs', I would like 'German Shepherd' but I would also like 'dog parks' and 'lemurs' assuming dogs get along well with lemurs. What would be the best way to approach this problem. In my head I have a massive many-to-many mapping, but I can't seem to translate it to code. Thanks for looking. FYI I'm using the sample project from here: http://mobile.tutsplus.com/tutorials/windows/introduction-to-xna-on-windows-phone-7/

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