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• std::map default value for build-in type

  - by Qifa Zhao

  Recently, I was confused by the std::map operator[] function. In the MSDN library, it says: "If the argument key value is not found, then it is inserted along with the default value of the data type." I tryed to search much more exactly explanation for this issue. For example here: std::map default value In this page, Michael Anderson said that "the default value is constructed by the default constructor(zero parameter constructor)". Now my quest comes to this:"what the default value for the build-in type?". Was it compiler related? Or is there a standard for this issue by the c++ stardard committee? I did a test on visual studio 2008 for the "int" type, and found the "int" type is construted with the value 0.

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• Objective-C categories: Can I add a property for a method not in my category?

  - by Squeegy

  I want to use a category to make a method on the original class available as a property as well. Class A: @interface ClassA - (NSString*)foo; @end Class A category @interface ClassA (Properties) - (void)someCategoryMethod; @property (nonatomic, readonly) NSString *foo; @end Now when I do this, it seems to work, but it gives me warnings because I am not synthesizing the property in my category implementation. How do I tell the compiler everything is actually just fine since the original class synthesizes the property for me?

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• Do I have to create a static library to test my application?

  - by Christopher Gateley

  I'm just getting started with TDD and am curious as to what approaches others take to run their tests. For reference, I am using the google testing framework, but I believe the question is applicable to most other testing frameworks and to languages other than C/C++. My general approach so far has been to do either one of three things: Write the majority of the application in a static library, then create two executables. One executable is the application itself, while the other is the test runner with all of the tests. Both link to the static library. Embed the testing code directly into the application itself, and enable or disable the testing code using compiler flags. This is probably the best approach I've used so far, but clutters up the code a bit. Embed the testing code directly into the application itself, and, given certain command-line switches either run the application itself or run the tests embedded in the application. None of these solutions are particularly elegant... How do you do it?

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• Is there a way to make `enum` type to be unsigned?

  - by Kirill V. Lyadvinsky

  Is there a way to make enum type to be unsigned? The following code gives me a warning about signed/unsigned comparison. enum EEE { X1 = 1 }; int main() { size_t x = 2; EEE t = X1; if ( t < x ) std::cout << "ok" << std::endl; return 0; } I've tried to force compiler to use unsigned underlying type for enum with the following: enum EEE { X1 = 1, XN = 18446744073709551615LL }; But that still gives the warning.

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• Scala and the Java Memory Model

  - by Ben Lings

  The Java Memory Model (since 1.5) treats final fields differently to non-final fields. In particular, provided the this reference doesn't escape during construction, writes to final fields in the constructor are guaranteed to be visible on other threads even if the object is made available to the other thread via a data race. (Writes to non-final fields aren't guaranteed to be visible, so if you improperly publish them, another thread could see them in a partially constructed state.) Is there any documentation on how/if the Scala compiler creates final (rather than non-final) backing fields for classes? I've looked through the language specification and searched the web but can't find any definitive answers. (In comparison the @scala.volatile annotation is documented to mark a field as volatile)

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• Divide and conquer of large objects for GC performance

  - by Aperion

  At my work we're discussing different approaches to cleaning up a large amount of managed ~50-100MB memory.There are two approaches on the table (read: two senior devs can't agree) and not having the experience the rest of the team is unsure of what approach is more desirable, performance or maintainability. The data being collected is many small items, ~30000 which in turn contains other items, all objects are managed. There is a lot of references between these objects including event handlers but not to outside objects. We'll call this large group of objects and references as a single entity called a blob. Approach #1: Make sure all references to objects in the blob are severed and let the GC handle the blob and all the connections. Approach #2: Implement IDisposable on these objects then call dispose on these objects and set references to Nothing and remove handlers. The theory behind the second approach is since the large longer lived objects take longer to cleanup in the GC. So, by cutting the large objects into smaller bite size morsels the garbage collector will processes them faster, thus a performance gain. So I think the basic question is this: Does breaking apart large groups of interconnected objects optimize data for garbage collection or is better to keep them together and rely on the garbage collection algorithms to processes the data for you? I feel this is a case of pre-optimization, but I do not know enough of the GC to know what does help or hinder it.

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• Interview - Program on Computer

  - by Gilad Naor

  Spent some time searching, couldn't find exactly what I'm after. We like giving hands-on programming exercises as part of the interview process. The interviewee gets a laptop, with the editor and compiler of his choice. He or she then get a programming exercise and has about an hour to code it. Depending on the nature of the question, internet access is either allowed or forbidden. I'm looking for good general questions for a junior developer. I don't care what language they choose to program in. C++ is as good as Python or Scheme, as long as (s)he can program in it (this rules out "can you write a correct copy-constructor" style questions). I just want to see how they code, if their code is self-documenting, if they write tests, check edge-cases, etc. What kind of questions would you ask?

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• Reasons to learn MSIL

  - by mannu

  Hi, Learning MSIL is fun and all that. Understanding what is going on "under the hood" can in many ways improve how you write your code performance-wise. However, the IL that is produced by the compiler is quite verbose and does not tell the whole story since JIT will optimize away a lot of the code. I, personally, have had good use of my very basic IL understanding when I've had to make a small fix in an assembly I do not have the source code for. But, I could as well have used Reflector to generate C# code. I would like to know if you've ever had good use of MSIL understanding and/or why you think it is worth learning it (except for the fun in it, of course). I'd also like to know if you think one should not learn it and why.

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• How can I access IEnumerable<T> extension methods on my custom subclass of BindingList<T>?

  - by Dan

  I have a custom subclass of BindingList<T> that I want to execute a LINQ query over using the handy extension methods. For example: public int GetSum(MyList<T> list) { return list.Sum(x => x.Value); } But the compiler complains that it can't resolve Sum because it doesn't recognize list as an IEnumerable<T>, which it obviously is, because this works: public int GetSum(MyList<T> list) { return ((IEnumerable<T>)list).Sum(x => x.Value); } Anyone have a clever way I can avoid the ugly and unecessary cast?

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• What are differences between AssemblyVersion, AssemblyFileVersion and AssemblyInformationalVersion?

  - by Jakub Šturc

  There are three assembly version attributes. What are differences? Is it ok if I use AssemblyVersion and ignore the rest? MSDN says: AssemblyVersion: Specifies the version of the assembly being attributed. AssemblyFileVersion: Instructs a compiler to use a specific version number for the Win32 file version resource. The Win32 file version is not required to be the same as the assembly's version number. AssemblyInformationalVersion: Defines additional version information for an assembly manifest. This is follow up to What are the best practices for using Assembly Attributes?

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• C# ASP.Net The type or namespace name 'iAnywhere' could not be found

  - by Louis Russell

  Morning all, I know that this sounds like a simple referencing problem from the title this is becoming a nightmare! I have a code class that uses the "iAnywhere.Data.AsaClient.dll". This Dll is referenced in the project and in the code class I have added this dll in the Using section. Everything seems fine at build with no errors at all but when I go to run the application it comes up with the following Compilation Error: Compiler Error Message: CS0246: The type or namespace name 'iAnywhere' could not be found (are you missing a using directive or an assembly reference?) The line that the Error points to this line in the class: using iAnywhere.Data.AsaClient; I have set the dll to copy local and it makes no difference, the Dll is installed on my PC so is in the GAC, I use this Dll with many other C# projects and have no problems. I have scoured Google looking for an answer and haven't found anything that points me to an answer to my problem. Any help would be brilliant!

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• Error including image in Latex

  - by euphoria83

  I am getting the following error while compiling my Latex File : ! LaTeX Error: Cannot determine size of graphic in tree.jpg (no BoundingBox). Why do I get this error ? What has this to do with an .eps file ? Infact, I could compile it fine with MacTex on my machine. But when I submit it online to a scientific journal for publication, it compiles it on the server and sends me the resultant PDF which as all these error that prevent it from compiling. I am using the following syntax for including the images : \begin{figure}[!h] \begin{center} \scalebox{0.45}{ \includegraphics{tree.jpg}} \end{center} \caption{\small A sample} \label{tree} \end{figure} What should I do ? Could it be that their server is using an old compiler ? UPDATE : It finally worked. I converted the first image to PDF and the compilation happened perfectly. I guess it used the bounding box value from that PDF and applied it to all images.

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• Assigning an @Annotation enum a value

  - by h2g2java

  I created enum Restrictions{ none, enumeration, fractionDigits, length, maxExclusive, maxInclusive, maxLength, minExclusive, minInclusive, minLength, pattern, totalDigits, whiteSpace; public Restrictions setValue(int value){ this.value = value; return this; } public int value; } So that I could happily do something like this, which is perfectly legal syntax. Restrictions r1 = Restrictions.maxLength.setValue(64); The reason being is, I am using enum to restrict the type of restriction that could be used, and be able to assign a value to that restriction. However, my actual motivation is to use that restriction in an @annotation. @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD}) public @interface Presentable { Restrictions[] restrictions() default Restrictions.none; } So that, I intended to do this: @Presentable(restrictions=Restrictions.maxLength.setValue(64)) public String userName; to which, the compiler croaks The value for annotation enum attribute must be an enum constant expression. Is there a way to accomplish what I wish to accomplish

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• Using C# and gppg, how would I construct an abstract syntax tree?

  - by Rupert

  Is there a way to do this almost out-of-the-box? I could go and write a big method that would use the collected tokens to figure out which leaves should be put in which branches and in the end populate a TreeNode object, but since gppg already handled everything by using supplied regular expressions, I was wondering if there's an easier way? Even if not, any pointers as to how best to approach the problem of creating an AST would be appreciated. Apologies if I said anything silly, I'm only just beginning to play the compiler game. :)

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• How can I compare market data feed sources for quality and latency improvement?

  - by yves Baumes

  I am in the very first stages of implementing a tool to compare 2 market data feed sources in order to prove the quality of new developed sources to my boss ( meaning there are no regressions, no missed updates, or wrong ), and to prove latencies improvement. So the tool I need must be able to check updates differences as well as to tell which source is the best (in term of latency). Concrectly, reference source could be Reuters while the other one is a Feed handler we develop internally. People warned me that updates might not arrive in the same order as Reuters implementation could differs totally from ours. Therefore a simple algorithm based on the fact that updates could arrive in the same order is likely not to work. My very first idea would be to use fingerprint to compare feed sources, as Shazaam application does to find the title of the tube you are submitting. Google told me it is based on FFT. And I was wondering if signal processing theory could behaves well with market access applications. I wanted to know your own experience in that field, is that possible to develop a quite accurate algorithm to meet the needs? What was your own idea? What do you think about fingerprint based comparison?

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• Haskell Syntax: Parse Error On Input

  - by NuNu

  As part of a mini-haskell compiler that I'm writing, I have a function named app. What I want this function to do is take in these arguments epp (App e1 e2). The first step would be to evaluate e1 recursively (epp e1) and check if the output would be an error. If not then evaluate e2 and then call another function eppVals to evaluate the outputs of the calls on e1 and e2 which I defined as v1 and v2 respectively. epp (App e1 e2) | epp e1 /= Error = eppVals v1 v2 | otherwise = Error where v1 = epp e1 v2 = epp e2 <- parse error on input `=' Logically I believe what I have written so far works but I'm getting a parse error on input = where I stated above. Any idea why? My second try epp :: Exp -> Error Val epp (App e1 e2) = (eppVals v1 v2) where v1 = (epp e1) v2 = (epp e2) But now throws Couldn't match expected type Val with actual type Error Val

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• maven compile fails because i have a non-maven jar

  - by pstanton

  i have a couple of internal libraries which i haven't/don't know how to add to my local maven repository. i've added them to the project's classpath but my maven-compile failes stating that it can't find the classes in the external jars (as expected): [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.0.2:compile (default-compile) on project proj: Compilation failure: Compilation failure: dir\src\main\java\package\MyClass.java:[8,25] package blah does not exist dir\src\main\java\package\MyClass.java:[9,25] package blah does not exist dir\src\main\java\package\MyClass.java:[21,12] cannot find symbol symbol : variable Blah location: class package.MyClass dir\src\main\java\package\MyClass.java:[28,9] cannot find symbol symbol : variable Blah location: class package.MyClass how do i tell maven about a jar i've sneakily added to my project's classpath so it can use it to compile?

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• PEAR mail not sending to .eu email addresses

  - by andy-score

  I have a PEAR mailing script that is used to send newsletters from a clients website. I've used the same code before to produce another newsletter system and it has worked well and been used to send emails to various addresses, however our latest client has email addresses ending .eu and this seems to cause a problem. When the newsletter is sent from the site to the various subscribers, including gmail, hotmail, yahoo and our own company emails, the emails are received correctly by all but the clients email addresses, the ones ending in .eu. As there is nothing different between their mailing system and our own, which is run from the same hosting company, I have to conclude that it is something to do with the domain name. The emails are being sent to the addresses from the system, as I have a log file storing the email addresses when the mail out function is called, but the newsletter never appears in the inbox. I have created a new email account for the domain and that too isn't receiving the emails. It's not going into a spam folder as the webmail system marks spam by adding SPAM into the subject. I've tried to log if there are any errors using the following foreach($subscribers as $recipient) { $send_newsletter = $mail->send($recipient, $headers, $body); // LOG INFO $message = $recipient; if($send_newsletter) { $message .= ' SENT'; } elseif(PEAR::isError($send_newsletter)) { $message .= ' ERROR: '.$send_newsletter->getMessage(); } $message .= ' | '; fwrite($log_file,$message); } However this simple returns SENT for all recipients, so in theory there isn't anything wrong with the mailing function. I don't know a great deal about PEAR or the mailing function so I may be missing something important, but I'd have thought seeing the last thing to happen is sending the email out, and that seems to work, then it should reach the clients inbox. Is this something to do with the PEAR mailing function not liking .eu addresses or is it more likely to be something wrong in my code or with their domain? Any help is greatly appreciated as the client and myself are getting both confused and frustrated by the whole thing. Cheers

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• How can I find a package?

  - by Roman

  In my code I have the following statement import com.apple.dnssd.*; and compiler (javac) complains about this line. It writes that the package does not exist. But I think that it could be that "javac" search the package in a wrong place (directory). In this respect I have two questions: How can I know where javac search for the packages? I think that it is very likely that I have the above mentioned package but I do not know where it is located. What are the typical place to look for the packages?

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• Naming convention in Objective C /C , start with "_"?

  - by Tattat

  Something I see ppl define the variable like this: b2World *_world; b2Body *_body; CCSprite *_ball; instead of b2World *world; b2Body *body; CCSprite *ball; I familiar with the second one, but not the first one. So, I checked the Wikipedia about naming convention: Names beginning with double underscore or an underscore and a capital letter are reserved for implementation (compiler, standard library) and should not be used (e.g. __reserved or _Reserved). So, is that any special meaning which is start with "_"? The wiki page.

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• CString error, 'CString': is not a member of 'ATL::CStringT<BaseType, StringTraits>'

  - by flavour404

  Hi, I am trying to do this: #include <atlstr.h> CHAR Filename; // [sp+26Ch] [bp-110h]@1 char v31; // [sp+36Ch] [bp-10h]@1 int v32; // [sp+378h] [bp-4h]@1 GetModuleFileNameA(0, &Filename, 0x100u); CString::CString(&v31, &Filename); But I am getting the compiler error C2039:'CString': is not a member of 'ATL::CStringT' This is a non MFC based dll, but according to the docs you should be able to use CString functionality with the include #include atlstr.h how do I make it work? Thanks

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• Unchecked call to compareTo

  - by Dave Jarvis

  Background Create a Map that can be sorted by value. Problem The code executes as expected, but does not compile cleanly: http://pastebin.com/bWhbHQmT The syntax for passing Comparable as a generic parameter along to the Map.Entry<K, V> (where V must be Comparable?) -- so that the (Comparable) typecast shown in the warning can be dropped -- eludes me. Warning Compiler's cantankerous complaint: SortableValueMap.java:24: warning: [unchecked] unchecked call to compareTo(T) as a member of the raw type java.lang.Comparable return ((Comparable)entry1.getValue()).compareTo( entry2.getValue() ); Question How can the code be changed to compile without any warnings (without suppressing them while compiling with -Xlint:unchecked)? Related TreeMap sort by value How to sort a Map on the values in Java? http://paaloliver.wordpress.com/2006/01/24/sorting-maps-in-java/ Thank you!

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• SubSonic 3.0 - Save method with all columns as parameters?

  - by Todd Menier

  Hi, Just getting started with SubSonic. I'm using the Repository pattern, so my domain objects are totally seperate, and SubSonic-generated classes are used only in my data access layer. I'm wondering if a template exists that will give me a Save method (Insert/Update) that requires all table column values as parameters. My thinking is that since I need to do the mapping work manually, at least if my database schema changes (ie, a new column is added), I won't forget to add a corresponding mapping, since the auto-generated method signature would change and the compiler would catch it. I've considered messing with the T4 templates to add this feature, but thought I'd check if this already exists somewhere before I head down that path. Thanks in advance.

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• Use WM_COPYDATA to send data between processes

  - by Charles Gargent

  I wish to send text between processes. I have found lots of examples of this but none that I can get working. Here is what I have so far: for the sending part: COPYDATASTRUCT CDS; CDS.dwData = 1; CDS.cbData = 8; CDS.lpData = NULL; SendMessage(hwnd, WM_COPYDATA , (WPARAM)hwnd, (LPARAM) (LPVOID) &CDS); the receiving part: case WM_COPYDATA: COPYDATASTRUCT* cds = (COPYDATASTRUCT*) lParam; I dont know how to construct the COPYDATASTRUCT, I have just put something in that seems to work. When debugging the WM_COPYDATA case is executed, but again I dont know what to do with the COPYDATASTRUCT. I would like to send text between the two processes. As you can probably tell I am just starting out, I am using GNU GCC Compiler in Code::Blocks, I am trying to avoid MFC and dependencies.

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• F# - This code isn't compiling for me

  - by stacker

  This code isn't compiling for me: let countDown = [5L .. -1L .. 0L];; I have a book that says it should return this: val countDown : int list = [5L; 4L; 3L; 2L; 1L; 0L] Compiler Error: Program.fs(42,24): error FS0010: Unexpected character '-' in expression > > let countDown = [5L .. -1L .. 0L];; let countDown = [5L .. -1L .. 0L];; -----------------------^

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