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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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• With PascalMock how do I mock a method with an untyped out parameter and an open array parameter?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all?

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• how do i execute a stored procedure with vici coolstorage?

  - by lincolnk

  I'm building an app around Vici Coolstorage (asp.net version). I have my classes created and mapped to my database tables and can pull a list of all records fine. I've written a stored procedure where the query jumps across databases that aren't mapped with Coolstorage, however, the fields in the query result map directly to one of my classes. The procedure takes 1 parameter. so 2 questions here: how do i execute the stored procedure? i'm doing this CSParameterCollection collection = new CSParameterCollection(); collection.Add("@id", id); var result = Vici.CoolStorage.CSDatabase.RunQuery("procedurename", collection); and getting the exception "Incorrect syntax near 'procedurename'." (i'm guessing this is because it's trying to execute it as text rather than a procedure?) and also, since the class representing my table is defined as abstract, how do i specify that result should create a list of MyTable objects instead of generic or dynamic or whatever objects? if i try Vici.CoolStorage.CSDatabase.RunQuery<MyTable>(...) the compiler yells at me for it being an abstract class.

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• What are the benefits of the PHP the different PHP compression libraries?

  - by Christopher W. Allen-Poole

  I've been looking into ways to compress PHP libraries, and I've found several libraries which might be useful, but I really don't know much about them. I've specifically been reading about bcompiler and PHAR libraries. Is there any performance benefit in either of these? Are there any "gotchas" I need to watch out for? What are the relative benefits? Do either of them add to/detract from performance? I'm also interested in learning of other libs which might be out there which are not obvious in the documentation? As an aside, does anyone happen to know whether these work more like zip files which just happen to have the code in there, or if they operate more like Python's pre-compiling which actually runs a pseudo-compiler? ======================= EDIT ======================= I've been asked, "What are you trying to accomplish?" Well, I suppose the answer is that this is all hypothetical. It is a combination of these: What if my pet project becomes the most popular web project on earth and I want to distribute it quickly and easily? (hay, a man can dream, right?) It also seems if using PHAR can be done easily, it would be the best way to create a subversion snapshot. Python has this really cool pre-compiling policy, I wonder if PHP has something like that? These libraries seem to do something similar. Will they do that? Hey, these libraries seem pretty neat, but I'd like clarification on the differences as they seem to do the same thing

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• How close can I get C# to the performance of C++ for small intensive tasks?

  - by SLC

  I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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• How can I get bitfields to arrange my bits in the right order?

  - by Jim Hunziker

  To begin with, the application in question is always going to be on the same processor, and the compiler is always gcc, so I'm not concerned about bitfields not being portable. gcc lays out bitfields such that the first listed field corresponds to least significant bit of a byte. So the following structure, with a=0, b=1, c=1, d=1, you get a byte of value e0. struct Bits { unsigned int a:5; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); (Actually, this is C++, so I'm talking about g++.) Now let's say I'd like a to be a six bit integer. Now, I can see why this won't work, but I coded the following structure: struct Bits2 { unsigned int a:6; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); Setting b, c, and d to 1, and a to 0 results in the following two bytes: c0 01 This isn't what I wanted. I was hoping to see this: e0 00 Is there any way to specify a structure that has three bits in the most significant bits of the first byte and six bits spanning the five least significant bits of the first byte and the most significant bit of the second? Please be aware that I have no control over where these bits are supposed to be laid out: it's a layout of bits that are defined by someone else's interface.

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• calling template function without <>; type inference

  - by Oops

  Hi, if I have a function template with typename T, where the compiler can set the type by itself, I do not have to write the type explicitely when I call the function like: template < typename T > T min( T v1, T v2 ) { return ( v1 < v2 ) ? v1: v2; } int i1 = 1, i2 = 2; int i3 = min( i1, i2 ); //no explicit <type> but if I have a function template with two different typenames like... template < typename TOut, typename TIn > TOut round( TIn v ) { return (TOut)( v + 0.5 ); } double d = 1.54; int i = round<int>(d); //explicit <int> Is it true that I have to specify at least 1 typename, always? I assume the reason is because C++ can not distinguish functions between different return types, true? but if I use a void function and handover a reference, again I must not explicitely specify the return typename: template < typename TOut, typename TIn > void round( TOut & vret, TIn vin ) { vret = (TOut)(vin + 0.5); } double d = 1.54; int i; round(i, d); //no explicit <int> should the conclusion be to avoid functions with return and more prefer void functions that return via a reference when writing templates? Or is there a possibility to avoid explicitely writing the return type? something like "type inference" for templates... is "type inference" possible in C++0x? I hope I was not too unclear. many thanks in advance Oops

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• write to fifo/pipe from shell, with timeout

  - by Tim

  I have a pair of shell programs that talk over a named pipe. The reader creates the pipe when it starts, and removes it when it exits. Sometimes, the writer will attempt to write to the pipe between the time that the reader stops reading and the time that it removes the pipe. reader: while condition; do read data <$PIPE; do_stuff; done writer: echo $data >>$PIPE reader: rm $PIPE when this happens, the writer will hang forever trying to open the pipe for writing. Is there a clean way to give it a timeout, so that it won't stay hung until killed manually? I know I can do #!/bin/sh # timed_write <timeout> <file> <args> # like "echo <args> >> <file>" with a timeout TIMEOUT=$1 shift; FILENAME=$1 shift; PID=$$ (X=0; # don't do "sleep $TIMEOUT", the "kill %1" doesn't kill the sleep while [ "$X" -lt "$TIMEOUT" ]; do sleep 1; X=$(expr $X + 1); done; kill $PID) & echo "$@" >>$FILENAME kill %1 but this is kind of icky. Is there a shell builtin or command to do this more cleanly (without breaking out the C compiler)?

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• How to force the build to be out of date, when a text file is modified?

  - by demoncodemonkey

  The Scenario My project has a post-build phase set up to run a batch file, which reads a text file "version.txt". The batch file uses the information in version.txt to inject the DLL with a version block using this tool. The version.txt is included in my project to make it easy to modify. It looks a bit like this: @set #Description="TankFace Utility Library" @set #FileVersion="0.1.2.0" @set #Comments="" Basically the batch file renames this file to version.bat, calls it, then renames it back to version.txt afterwards. The Problem When I modify version.txt (e.g. to increment the file version), and then press F7, the build is not seen as out-of-date, so the post-build step is not executed, so the DLL's version doesn't get updated. I really want to include the .txt file as an input to the build, but without anything actually trying to use it. If I #include the .txt file from a CPP file in the project, the compiler fails because it obviously doesn't understand what "@set" means. If I add /* ... */ comments around the @set commands, then the batch file has some syntax errors but eventually succeeds. But this is a poor solution I think. So... how would you do it?

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• Convert Form to UserControl

  - by Joe

  I have a 3rd party code library that I'm using; part of this library is a winforms application for editing the configuration files used by this library. I would like to embed their configuration editor app into my application. I have the source code to their library and the configuration editor is (as far as I can tell) a straight forward Winforms app using standard controls. I'm trying to convert the app's main form into a UserControl so that I can host it inside my application which is WPF (WPF's WindowsFormsHost won't host a Form object, I get an exception). I changed the form object to inherit from UserControl instead of Form and fixed all the compiler errors (there weren't many, just property initializations that don't exist on UserControls) but what's happening is my newly converted control is just blank. When I run my test app I don't see any of the controls that make up the original form, just a blank page. Any ideas? I really don't want to have to re-implement their app from scratch, that would suck. Edit: I forgot to mention I'm testing this in a WinForms application, not WPF, to just get the control working before trying to use it from WPF.

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• Setting Up OpenCV and .lib files

  - by jhaip

  I have been trying to set up OpenCV for the past few days with no results. I am using Windows 7 and VS C++ 2008 express edition. I have downloaded and installed OpenCV 2.1 and some of the examples work. I downloaded CMake and ran it to generate the VS project files and built all of them but there with several errors, and couldn't get any farther than that. When I ran CMake I configured it to use the VS 9 compiler, and then it brought up a list of items in red such as BUILD_EXAMPLES, BUILD_LATEX_DOCS, ect. All of them were unchecked except BUILD_NEW_PYTHON_SUPPORT, BUILD_TESTS, ENABLE_OPENMP, and OPENCV_BUILD_3RDPARTY_LIBS. I configured and generate without changing anything and then it generated the VS files such as ALL_BUILD.vcproj. I built the OpenCV VS solution in debug mode and it had 15 failures (maybe this is part of the problem or is it because I don't have python and stuff like that?) Now there was a lib folder created after building but inside there was just this VC++ Minimum Rebuild Dependency file and Program Debug Database file, both called cvhaartraining. I believe it should have created the .lib files I need instead of this. Also, the bin folder now has a folder called Debug with the same types of files with names like cv200d and cvaux200d. Believe I need those .lib files to move forward. I would also greatly appreciate if someone could direct me to a reliable tutorial to set up VS for OpenCV because I have been reading a lot of tutorials and they all say different things such as some say to configure Window's environment variables and other say files are located in folders such as OpenCV/cv which I don't have. I have gotten past the point of clear headed thinking so if anyone could offer some direction or a simple list of the files I need to link then I would be thankful. Also a side question: why when linking the OpenCV libs do you have to put them in quotes?

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• Creating spotlight in OpenGL scene

  - by Victor Oliveira

  Im studying OpenGL and trying to create a spot light at my application. The code that Im using for my #vertex-shader is below: #:vertex-shader #{ #version 150 core in vec3 in_pos; in vec2 in_tc; out vec2 tc; glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 20.0f); GLfloat spot_direction[] = { -1.0, -1.0, 0.0 }; glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction); glEnable(GL_LIGHT0); void main() { vec4 pos= vec4(vec3(1.0)*in_pos - vec3(1.0), 1.0); pos.z=0.0; gl_Position = pos; tc = in_tc; } } The thing is, everytime Im trying to run the code an Error that says: Type: other, Source: api, ID: 131169, Severity: low Message: Framebuffer detailed info: The driver allocated storage for renderbuffer 1. len = 157, written = 0 failed to compile vertex shader of deferred: directional info log for shader deferred: directional vertex info log for shader deferred: directional: ERROR: Unbound variable: when Specifications: Renderer: GeForce GTX 580/PCIe/SSE2 Version: 3.3.0 NVIDIA 319.17 GLSL: 3.30 NVIDIA via Cg compiler Status: Using GLEW 1.9.0 1024 x 768 OS: Linux debian I guess to create this spotlight is pretty much simple, but since Im really new to OpenGL I dont have a clue how to do it until now, even reading sources like: http://www.glprogramming.com/red/chapter05.html#name3 Read also in some place that light spots can get really hard to understand, but I cant avoid this step right now since Im following my lecture schedule. Could anybody help me?

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• Whats the wrong with this code?

  - by girinie

  Hi in this code first I am downloading a web-page source code then I am storing the code in text file. Again I am reading that file and matching with the regex to search a specific string. There is no compiler error. Exception in thread "main" java.lang.NoClassDefFoundError: java/lang/CharSequence Can anybody tell me Where I am wrong. import java.io.*; import java.net.*; import java.lang.*; import java.util.regex.Matcher; import java.util.regex.Pattern; public class WebDownload { public void getWebsite() { try{ URL url=new URL("www.gmail.com");// any URL can be given URLConnection urlc=url.openConnection(); BufferedInputStream buffer=new BufferedInputStream(urlc.getInputStream()); StringBuffer builder=new StringBuffer(); int byteRead; FileOutputStream fout; StringBuffer contentBuf = new StringBuffer(); while((byteRead=buffer.read()) !=-1) { builder.append((char)byteRead); fout = new FileOutputStream ("myfile3.txt"); new PrintStream(fout).println (builder.toString()); fout.close(); } BufferedReader in = new BufferedReader(new FileReader("myfile3.txt")); String buf = null; while ((buf = in.readLine()) != null) { contentBuf.append(buf);contentBuf.append("\n"); } in.close(); Pattern p = Pattern.compile("<div class=\"summarycount\">([^<]*)</div>"); Matcher matcher = p.matcher(contentBuf); if(matcher.find()) { System.out.println(matcher.group(1)); } else System.out.println("could not find"); } catch(MalformedURLException ex) { ex.printStackTrace(); } catch(IOException ex){ ex.printStackTrace(); } } public static void main(String [] args) { WebDownload web=new WebDownload(); web.getWebsite(); } }

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• ArrayList in Java, adding code to methods

  - by yaz

  Why am I getting a compile time error for the two method headers at the end of my code in my class ArrayListTest? ArrayListTest: http://pastebin.com/dUHn9vPr Student: http://pastebin.com/3Vz1Aytr I have a compiler error at the two lines: delete(CS242, s3) replace(CS242, s, s4); When I try to run the code it states: Exception in thread "main" java.lang.Error: Unresolved compilation problems: The method replace(ArrayList<Student>, Student, Student)in the type ArrayListTest is not applicable for the arguments (List<Student>, Student, Student) The method delete(ArrayList<Student>, Student) in the type ArrayListTest is not applicable for the arguments (List<Student>, Student) at ArrayListTest.main(ArrayListTest.java:54) I fixed the compile time errors since I use Eclipse and Eclipse gives options of code you can use to fix the compile time error. I chose to "Change method to 'replace(ArrayList, Student, Student)' to 'replace(List, Student, Student)' Although it fixed that compile time error, I don't understand why I was getting a compile time error to begin with and why that effectively fixed the error I don't really know what missing code I need to write to correct these two methods below: public static void replace(List<Student> cS242, Student oldItem, Student newItem) { public static void delete(List<Student> cS242, Student target){

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• linq - how to sort a list

  - by Billy Logan

  Hello everyone, I have a linq query that populates a list of designers. since i am using the filters below my sorting is not functioning properly. My question is with the given code below how can i best sort this List after the fact or sort while querying? I have tried to sort the list after the fact using the following script but i receive a compiler error: List<TBLDESIGNER> designers = new List<TBLDESIGNER>(); designers = 'calls my procedure below and comes back with an unsorted list of designers' designers.Sort((x, y) => string.Compare(x.FIRST_NAME, y.LAST_NAME)); Query goes as follows: List<TBLDESIGNER> designer = null; using (SOAE strikeOffContext = new SOAE()) { //Invoke the query designer = AdminDelegates.selectDesignerDesigns.Invoke(strikeOffContext).ByActive(active).ByAdmin(admin).ToList(); } Delegate: public static Func<SOAE, IQueryable<TBLDESIGNER>> selectDesignerDesigns = CompiledQuery.Compile<SOAE, IQueryable<TBLDESIGNER>>( (designer) => from c in designer.TBLDESIGNER.Include("TBLDESIGN") orderby c.FIRST_NAME ascending select c); Filter ByActive: public static IQueryable<TBLDESIGNER> ByActive(this IQueryable<TBLDESIGNER> qry, bool active) { //Return the filtered IQueryable object return from c in qry where c.ACTIVE == active select c; } Filter ByAdmin: public static IQueryable<TBLDESIGNER> ByAdmin(this IQueryable<TBLDESIGNER> qry, bool admin) { //Return the filtered IQueryable object return from c in qry where c.SITE_ADMIN == admin select c; } Thanks in advance, Billy

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• Creating circular generic references

  - by M. Jessup

  I am writing an application to do some distributed calculations in a peer to peer network. In defining the network I have two class the P2PNetwork and P2PClient. I want these to be generic and so have the definitions of: P2PNetwork<T extends P2PClient<? extends P2PNetwork<T>>> P2PClient<T extends P2PNetwork<? extends T>> with P2PClient defining a method of setNetwork(T network). What I am hoping to describe with this code is: A P2PNetwork is constituted of clients of a certain type A P2PClient may only belong to a network whose clients consist of the same type as this client (the circular-reference) This seems correct to me but if I try to create a non-generic version such as MyP2PClient<MyP2PNetwork<? extends MyP2PClient>> myClient; and other variants I receive numerous errors from the compiler. So my questions are as follows: Is a generic circular reference even possible (I have never seen anything explicitly forbidding it)? Is the above generic definition a correct definition of such a circular relationship? If it is valid, is it the "correct" way to describe such a relationship (i.e. is there another valid definition, which is stylistically preferred)? How would I properly define a non-generic instance of a Client and Server given the proper generic definition?

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• Invert a string: Recursion vs iteration in javascript

  - by steweb

  Hi all, one month ago I've been interviewed by some google PTO members. One of the questions was: Invert a string recursively in js and explain the running time by big O notation this was my solution: function invert(s){ return (s.length > 1) ? s.charAt(s.length-1)+invert(s.substring(0,s.length-1)) : s; } Pretty simple, I think. And, about the big-o notation, I quickly answered O(n) as the running time depends linearly on the input. - Silence - and then, he asked me, what are the differences in terms of running time if you implement it by iteration? I replied that sometimes the compiler "translate" the recursion into iteration (some programming language course memories) so there are no differences about iteration and recursion in this case. Btw since I had no feedback about this particular question, and the interviewer didn't answer "ok" or "nope", I'd like to know if you maybe agree with me or if you can explain me whether there could be differences about the 2 kind of implementations. Thanks a lot and Regards!

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• How to allow users to define financial formulas in a C# app

  - by Peter Morris

  I need to allow my users to be able to define formulas which will calculate values based on data. For example //Example 1 return GetMonetaryAmountFromDatabase("Amount due") * 1.2; //Example 2 return GetMonetaryAmountFromDatabase("Amount due") * GetFactorFromDatabase("Discount"); I will need to allow / * + - operations, also to assign local variables and execute IF statements, like so var amountDue = GetMonetaryAmountFromDatabase("Amount due"); if (amountDue > 100000) return amountDue * 0.75; if (amountDue > 50000) return amountDue * 0.9; return amountDue; The scenario is complicated because I have the following structure.. Customer (a few hundred) Configuration (about 10 per customer) Item (about 10,000 per customer configuration) So I will perform a 3 level loop. At each "Configuration" level I will start a DB transaction and compile the forumlas, each "Item" will use the same transaction + compiled formulas (there are about 20 formulas per configuration, each item will use all of them). This further complicates things because I can't just use the compiler services as it would result in continued memory usage growth. I can't use a new AppDomain per each "Configuration" loop level because some of the references I need to pass cannot be marshalled. Any suggestions?

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• Casting to a struct from LPVOID - C

  - by Jamie Keeling

  Hello, I am writing a simple console application which will allow me to create a number of threads from a set of parameters passed through the arguments I provide. DWORD WINAPI ThreadFunc(LPVOID threadData) { } I am packing them into a struct and passing them as a parameter into the CreateThread method and trying to unpack them by casting them to the same type as my struct from the LPVOID. I'm not sure how to cast it to the struct after getting it through so I can use it in the method itself, i've tried various combinations (Example attatched) but it won't compile. Struct: #define numThreads 1 struct Data { int threads; int delay; int messages; }; Call to method: HANDLE hThread; DWORD threadId; struct Data *tData; tData->threads = numThreads; tData->messages = 3; tData->delay = 1000; // Create child thread hThread = CreateThread( NULL, // lpThreadAttributes (default) 0, // dwStackSize (default) ThreadFunc, // lpStartAddress &tData, // lpParameter 0, // dwCreationFlags &threadId // lpThreadId (returned by function) ); My attempt: DWORD WINAPI ThreadFunc(LPVOID threadData) { struct Data tData = (struct Data)threadData; int msg; for(msg = 0; msg<5; msg++) { printf("Message %d from child\n", msg); } return 0; } Compiler error: error C2440: 'type cast' : cannot convert from 'LPVOID' to 'Data' As you can see I have implemented a way to loop through a number of messages already, I'm trying to make things slightly more advanced and add some further functionality.

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• How can I make a Maybe-Transformer MaybeT into an instance of MonadWriter?

  - by martingw

  I am trying to build a MaybeT-Transformer Monad, based on the example in the Real World Haskell, Chapter Monad Transformers: data MaybeT m a = MaybeT { runMT :: m (Maybe a) } instance (Monad m) => Monad (MaybeT m) where m >>= f = MaybeT $ do a <- runMT m case a of Just x -> runMT (f x) Nothing -> return Nothing return a = MaybeT $ return (Just a) instance MonadTrans MaybeT where lift m = MaybeT $ do a <- m return (Just a) This works fine, but now I want to make MaybeT an instance of MonadWriter: instance (MonadWriter w m) => MonadWriter w (MaybeT m) where tell = lift . tell listen m = MaybeT $ do unwrapped <- listen (runMT m) return (Just unwrapped) The tell is ok, but I can't get the listen function right. The best I could come up with after 1 1/2 days of constructor origami is the one you see above: unwrapped is supposed to be a tuple of (Maybe a, w), and that I want to wrap up in a Maybe-Type and put the whole thing in an empty MonadWriter. But the compiler complains with: Occurs check: cannot construct the infinite type: a = Maybe a When generalising the type(s) for `listen' In the instance declaration for `MonadWriter w (MaybeT m)' What am I missing?

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• How do I write test code to exercise a C# generic Pair<TKey, TValue> ?

  - by Scott Davies

  Hi, I am reading through Jon Skeet's "C# in Depth", first edition (which is a great book). I'm in section 3.3.3, page 84, "Implementing Generics". Generics always confuse me, so I wrote some code to exercise the sample. The code provided is: using System; using System.Collections.Generic; public sealed class Pair<TFirst, TSecond> : IEquatable<Pair<TFirst, TSecond>> { private readonly TFirst first; private readonly TSecond second; public Pair(TFirst first, TSecond second) { this.first = first; this.second = second; } ...property getters... public bool Equals(Pair<TFirst, TSecond> other) { if (other == null) { return false; } return EqualityComparer<TFirst>.Default.Equals(this.First, other.First) && EqualityComparer<TSecond>.Default.Equals(this.Second, other.Second); } My code is: class MyClass { public static void Main (string[] args) { // Create new pair. Pair thePair = new Pair(new String("1"), new String("1")); // Compare a new pair to previous pair by generating a second pair. if (thePair.Equals(new Pair(new string("1"), new string("1")))) System.Console.WriteLine("Equal"); else System.Console.WriteLine("Not equal"); } } The compiler complains: "Using the generic type 'ManningListing36.Paie' requires 2 type argument(s) CS0305" What am I doing wrong ? Thanks, Scott

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• How do I tell gcc to relax its restrictions on typecasting when calling a C function from C++?

  - by Daryl Spitzer

  I'm trying to use Cmockery to mock C functions called from C++ code. Because the SUT is in C++, my tests need to be in C++. When I use the Cmockery expect_string() macro like this: expect_string(mock_function, url, "Foo"); I get: my_tests.cpp: In function ‘void test_some_stuff(void**)’: my_tests.cpp:72: error: invalid conversion from ‘void*’ to ‘const char*’ my_tests.cpp:72: error: initializing argument 5 of ‘void _expect_string(const char*, const char*, const char*, int, const char*, int)’ I see in cmockery.h that expect_string is defined: #define expect_string(function, parameter, string) \ expect_string_count(function, parameter, string, 1) #define expect_string_count(function, parameter, string, count) \ _expect_string(#function, #parameter, __FILE__, __LINE__, (void*)string, \ count) And here's the prototype for _expect_string (from cmockery.h): void _expect_string( const char* const function, const char* const parameter, const char* const file, const int line, const char* string, const int count); I believe the problem is that I'm compiling C code as C++, so the C++ compiler is objecting to (void*)string in the expect_string_count macro being passed as the const char* string parameter to the _expect_string() function. I've already used extern "C" around the cmockery.h include in my_tests.cpp like this: extern "C" { #include <cmockery.h> } ...in order to get around name-mangling problems. (See "How do I compile and link C++ code with compiled C code?") Is there a command-line option or some other means of telling g++ how to relax its restrictions on typecasting from my test's C++ code to the C function in cmockery.c? This is the command I'm currently using to build my_tests.cpp: g++ -m32 -I ../cmockery-0.1.2 -c my_tests.cpp -o $(obj_dir)/my_tests.o

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• Keeping values on form after submition

  - by Lina

  Hi, I'm trying to keep the entered data in the form after submitting by using "value=..." I'm getting a compilation error on the following code: <form id="myform"> <input id="hour" type="text" name="hour" value="<%=hour%>" style="width:30px; text-align:center;" /> : <input id="minute" type="text" name="minute" value="<%=minute%>" style="width:30px; text-align:center;" /> <br/> <input type="submit" value="Validate!" /> </form> the error is : Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. Compiler Error Message: CS0103: The name 'hour' does not exist in the current context any solution? thanks a lot in advance, Lina

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• Why I do not see a static variable in a loop?

  - by Roman

  I have a static method which sets a variable: static String[] playersNames; public static void setParameters(String[] players) { playersNames = players; } Then I have a static block: static { JRadioButton option; ButtonGroup group = new ButtonGroup(); // Wright a short explanation of what the user should do. partnerSelectionPanel.add(new JLabel("Pleas select a partner:")); // Generate radio-buttons corresponding to the options available to the player. // Bellow is the problematic line causing the null pointer exception: for (String playerName: playersNames) { final String pn = playerName; option = new JRadioButton(playerName, false); option.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partner = pn; } }); partnerSelectionPanel.add(option); group.add(option); } partnerSelectionPanel.add(label); // Add the "Submit" button to the end of the "form". JButton submitButton = new JButton("Submit"); submitButton.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partnerSelected(); } }); partnerSelectionPanel.add(submitButton); } Compiler does not complain about anything but when I try to execute the code I get problems. In this place SelectPartnerGUI.setParameters(players); I have: Exception in thread "main" java.lang.ExceptionInitializerError. and it is cause by java.lang.NullpointerException at this place for (String playerName: playersNames). Does my program do not see the palyersNames?

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• Binding type variables that only occur in assertions

  - by Giuseppe Maggiore

  Hi! I find it extremely difficult to describe my problem, so here goes nothing: I have a bunch of assertions on the type of a function. These assertions rely on a type variable that is not used for any parameter of the function, but is only used for internal bindings. Whenever I use this function it does not compile because, of course, the compiler has no information from which to guess what type to bind my type variable. Here is the code: {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances, FlexibleContexts, EmptyDataDecls, ScopedTypeVariables, TypeOperators, TypeSynonymInstances #-} class C a a' where convert :: a -> a' class F a b where apply :: a -> b class S s a where select :: s -> a data CInt = CInt Int instance S (Int,String) Int where select (i,_) = i instance F Int CInt where apply = CInt f :: forall s a b . (S s a, F a b) => s -> b f s = let v = select s :: a y = apply v :: b in y x :: Int x = f (10,"Pippo") And here is the generated error: FunctorsProblems.hs:21:4: No instances for (F a Int, S (t, [Char]) a) arising from a use of `f' at FunctorsProblems.hs:21:4-17 Possible fix: add an instance declaration for (F a Int, S (t, [Char]) a) In the expression: f (10, "Pippo") In the definition of `x': x = f (10, "Pippo") Failed, modules loaded: none. Prelude>

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