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• Create an object in C# from an F# object with optional arguments

  - by Mark Pearl

  I have a object in F# as follows... type Person(?name : string) = let name = defaultArg name "" member x.Name = name I want to be able to create an instance of this object in a C# project. I have added as a reference the correct libraries to the project and can see the object via intellisense however I am not sure on the correct syntaxt to create an instance of the object. Currently I have the following in my C# project - which the compiler doesn't like... var myObj1 = new Person("mark");

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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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• 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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• ASP.net page gets error on import statement, but I do have the reference in place?

  - by Greg

  Hi, Any ideas why I am getting the below error in my MVC2 project, even through in the project itself I definitely have a reference to "system.Web.Entity"? Compiler Error Message: CS0234: The type or namespace name 'Entity' does not exist in the namespace 'System.Data' (are you missing an assembly reference?) Source Error: Line 1: <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<List<Node>>" %> Line 2: <%@ Import Namespace="TopologyDAL" %> Line 3: <%@ Import Namespace="System.Data.Entity" %> thanks

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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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• 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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• 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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• How does sizeof calculate the size of structures

  - by Gearoid Murphy

  I know that a char and an int are calculated as being 8 bytes on 32 bit architectures due to alignment, but I recently came across a situation where a structure with 3 shorts was reported as being 6 bytes by the sizeof operator. Code is as follows: #include <iostream> using namespace std ; struct IntAndChar { int a ; unsigned char b ; }; struct ThreeShorts { unsigned short a ; unsigned short b ; unsigned short c ; }; int main() { cout<<sizeof(IntAndChar)<<endl; // outputs '8' cout<<sizeof(ThreeShorts)<<endl; // outputs '6', I expected this to be '8' return 0 ; } Compiler : g++ (Debian 4.3.2-1.1) 4.3.2. This really puzzles me, why isn't alignment enforced for the structure containing 3 shorts?

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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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• How do I work with WIndows Forms in WPF?

  - by xarzu

  How do I work with WIndows Forms in WPF? In my WPF program I created a Windows Form class. In this Form, I placed an OK button and I went into the properties of the button and set the DialogResult to OK. Now, I am calling this Dialog (Window Form) from the MainWindow.xaml.cs: dres = form.ShowDialog(); if (dres != DialogResult.OK) return; The compiler is complaining: Error 3 'System.Nullable<bool>' does not contain a definition for 'OK' and no extension method 'OK' accepting a first argument of type 'System.Nullable<bool>' could be found (are you missing a using directive or an assembly reference?)

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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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• 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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• Anyone know how to use TValue.AsType<TNotifyEvent> properly?

  - by Mason Wheeler

  I'm trying to use RTTI to add an event handler to a control, that may already have an event handler set. The code looks something like this: var prop: TRttiProperty; val: TValue; begin prop := FContext.GetType(MyControl.ClassInfo).GetProperty('OnChange'); val := prop.GetValue(MyControl); FOldOnChange := val.AsType<TNotifyEvent>; prop.SetValue(MyControl, TValue.From<TNotifyEvent>(self.MyOnChange)); end; I want this so I can do this in MyOnChange: begin if assigned(FOldOnChange) then FOldOnChange(Sender); //additional code here end; Unfortunately, the compiler doesn't seem to like the line FOldOnChange := val.AsType<TNotifyEvent>;. It says E2010 Incompatible types: 'procedure, untyped pointer or untyped parameter' and 'TNotifyEvent' Anyone know why that is or how to fix it? It looks right to me...

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• gcc, UTF-8 and limits.h

  - by bobby

  My OS is Debian, my default locale is UTF-8 and my compiler is gcc. By default CHAR_BIT in limits.h is 8 which is ok for ASCII because in ASCII 1 char = 8 bits. But since I am using UTF-8, chars can be up to 32 bits which contradicts the CHAR_BIT default value of 8. If I modify CHAR_BIT to 32 in limits.h to better suit UTF-8, what do I have to do in order for this new value to come into effect ? I guess I have to recompile gcc ? Do I have to recompile the linux kernel ? What about the default installed Debian packages, will they work ?

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• fatal error F1002

  - by Ghazooo

  Hi , I have a Fortran 77 program code , I am using fortran power station on XP . I wrote this program because I am studying Master's degree in Mechanics , It is a very long Finite element method code. when I press the compile order it shows me the following message : "fatal error F1002: compiler is out of heap space in pass 2" I googled the problem , and found the following solutions : http://www.microsofttranslator.com/BV.aspx?ref=CSSKB&from=en&to=ar&a=http://support.microsoft.com/kb/112345/en-us?fr=1 But to be honest , I did not understand the solution !!! I think my code is good and clear . Does any one have any suggestions to solve this problem ?? please consider me as a very simple programmer. I will really appreciate that . Thanks in Advance Ghazooo

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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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• 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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• Hierarchical/Nested Database Structure for Comments

  - by Stephen Melrose

  Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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• Button outside view... how to make it work

  - by Mike

  I have a UIImageView based class that creates objects with the following characteristics: a small image square and a UITextView below. If the user drags the object by the image it can drag it around. If the user taps on the UITextView the keyboard has to appear and the user can change the text on it. The objects created by the class are like this: 1) the object creates a 60x60 pixels frame 2) puts an image inside that frame 3) creates a UITextView and puts it below that 60x60 frame. So, as the class is a UIImageView based and it creates an image with 60x60 pixels and the UITextView is located outside that area, in theory the text view is outside the area the tapping are for that object. Obviously I could make the class create a big square to encompass the image and the text view, but that frame would be too big and I have the objects created by this class to be as close as possible when I add them to another view. I could also create the text views from the same view I created the objects, but I would have to manage each object and each correspondent text view and I need them to move together... so, I have a problem. Any ideas on a simplest way to do that?

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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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• "Reference required" error when referencing NServiceBus assembly from another project

  - by cwegrzyn

  We are trying to write an application that uses the NServiceBus library in a VB.NET environment. We've been stymied by errors similar to the following: Reference required to assembly 'NServiceBus, Version=2.0.0.1071, Culture=neutral, PublicKeyToken=9fc386479f8a226c' containing the implemented interface 'NServiceBus.IMessageHandler`1'. Add one to your project. Our project already includes references to NServiceBus.dll and NServiceBus.Core.dll from the same NServiceBus 2.0 RC2 distribution. Steps to reproduce: Create a new VB Class Library Project (.NET 3.5) Add NServiceBus.dll and NServiceBus.Core.dll as References. Put the following code in Class1.vb: Imports NServiceBus.Sagas.Impl Class Test Public Function Foo() As SagaMessageHandler Return Nothing End Function End Class You should now see the compiler error mentioned above. An identical project written in C# has no compile errors. Any ideas about how to solve this problem? (And, yes, my preferred solution is switching to C#, but no, that's not an acceptable one at the moment.)

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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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• Could Grand Central Dispatch (`libdispatch`) ever be made available on Windows?

  - by elliottcable

  I’m looking into multithreading, and GCD seems like a much better option than manually writing a solution using pthread.h and pthreads-win32. However, although it looks like libdispatch is either working on, or soon going to be working on, most newer POSIX-compatible systems… I have to ask, what about Windows? What are the chances of libdispatch being ported to Windows? What are the barriers preventing that from happening? If it came down to it, what would I need to do to preform that portage? Edit: Some things I already know, to get the discussion started: We need a blocks-compatible compiler that will compile on Windows, no? Will PLBlocks handle that? Can we use the LLVM blocks runtime? Can’t we replace all the pthread.h dependencies in userspace libdispatch with APR calls, for portability? Or, alternatively, use pthreads-win32 I suppose…

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• C# huge size 2-dim arrays

  - by 4eburek

  I need to declare square matrices in C# WinForms with more than 20000 items in a row. I read about 2GB .Net object size limit in 32bit and also the same case in 64bit OS. So as I understood the single answer - is using unsafe code or separate library built withing C++ compiler. The problem for me is worth because ushort[20000,20000] is smaller then 2GB but actually I cannot allocate even 700MB of memory. My limit is 650MB and I don't understand why - I have 32bit WinXP with 3GB of memory. I tried to use Marshal.AllocHGlobal(700<<20) but it throws OutOfMemoryException, GC.GetTotalMemory returns 4.5MB before trying to allocate memory. I found only that many people say use unsafe code but I cannot find example of how to declare 2-dim array in heap (any stack can't keep so huge amount of data) and how to work with it using pointers. Is it pure C++ code inside of unsafe{} brackets? Could you please provide a small example of working with matrices using pointers in unsafe code.

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