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  • How can I implement the same behavior as Dictionary.TryGetValue

    - by pblasucci
    So, given then following code type MyClass () = let items = Dictionary<string,int>() do items.Add ("one",1) items.Add ("two",2) items.Add ("three",3) member this.TryGetValue (key,value) = items.TrygetValue (key,value) let c = MyClass () let d = Dictionary<string,int> () d.Add ("one",1) d.Add ("two",2) d.Add ("three",3) And the following test code let r1,v1 = d.TryGetValue "one" let r2,v2 = c.TryGetValue "one" The r1,v1 line works fine. The r2,v2 line bombs; complaining c.TryGetValue must be given a tuple. Interestingly, in each line the signature of TryGetValue is different. How can I get my custom implementation to exhibit the same behavior as the BCL version? Or, asked another way, since F# has (implicitly) the concept of tuple parameters, curried parameters, and BCL parameters, and I know how to distinguish between curried and tuple-style, how can I force the third style (a la BCL methods)? Let me know if this is unclear.

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  • Iterator blocks and inheritance.

    - by Dave Van den Eynde
    Given a base class with the following interface: public class Base { public virtual IEnumerable<string> GetListOfStuff() { yield return "First"; yield return "Second"; yield return "Third"; } } I want to make a derived class that overrides the method, and adds its own stuff, like so: public class Derived : Base { public override IEnumerable<string> GetListOfStuff() { foreach (string s in base.GetListOfStuff()) { yield return s; } yield return "Fourth"; yield return "Fifth"; } } However, I'm greeted with a warning that "access to a member through a base keyword from an iterator cannot be verified". What's the accepted solution to this problem then?

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  • Empty Structures compile in VB 10+

    - by Mark Hurd
    This is at least a documentation error, if not a bug. In VB.NET prior to .NET 4.0 (i.e. VB.NET 7 through 9) an empty Structure declaration fails at compile-time with error BC30281: Structure 'MySimpleEmpty' must contain at least one instance member variable or Event declaration. E.g. The following two structures compile successfully in VB10, and not prior: Structure MySimpleEmpty End Structure Public Structure AnotherEmpty Public Const StillEmpty As Boolean = True End Structure I note the documentation for the Error BC30281 stops at VB9, but the documentation for the Structure statement still has the datamemberdeclarations as required even as of VB11 (.NET 4.5 VS2012). These two Structures compile in VB11 (VS2012) as well. (Thanks John Woo.) Is there some blog entry or documentation confirming this is an intended change or a bug in VB10 and later?

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  • C: Pointers to any type?

    - by dragme
    I hear that C isn't so type-safe and I think that I could use that as an advantage for my current project. I'm designing an interpreter with the goal for the VM to be extremely fast, much faster than Ruby and Python, for example. Now I know that premature optimization "is the root of all evil" but this is rather a conceptual problem. I have to use some sort of struct to represent all values in my language (from number over string to list and map) Would the following be possible? struct Value { ValueType type; void* value; } I would store the actual values elsewhere, e.g: a separate array for strings and integers, value* would then point to some member in this table. I would always know the type of the value via the type variable, so there wouldn't be any problems with type errors. Now: Is this even possible in terms of syntax and typing?

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  • QList as a function parameter - Linking Error - LNK2019

    - by user2445136
    I have an issue with QList as a function parameter and I'll be glad if you can assist me. I have this code for example: void SpinBoxList_Enable(QList spinBoxList) { foreach(QWidget mWidget,*spinBoxList) mWidget-setEnabled(false); } and in the implemantation file I use the QList variable as a pointer: SpinBoxList_Enable(&controlBoardSpinBoxList); ( controlBoardSpinBoxList is a variable of QList ). The Function ToggleBoards_Slot(bool) is a slot that uses When I compile, I get this error message: 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Disable(class QList *)" (?SpinBoxList_Disable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "public: void __cdecl CMosaixSerialNumber::ToggleBoards_Slot(bool)" (?ToggleBoards_Slot@CMosaixSerialNumber@@QEAAX_N@Z) 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Enable(class QList *)" (?SpinBoxList_Enable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "private: void __cdecl CMosaixSerialNumber::on_ControlBoardCheckBox_StateChanged(int)" (?on_ControlBoardCheckBox_StateChanged@CMosaixSerialNumber@@AEAAXH@Z) How can I fix this ? Thanks, EVH671

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  • Is there a leak in this copy code?

    - by Don Wilson
    Is there a leak in this code? // Move the group Group *movedGroup = [[Group alloc] init]; movedGroup = [[[[GroupList sharedGroupList] groups] objectAtIndex:fromIndex] copy]; [[GroupList sharedGroupList] deleteGroup:fromIndex]; [[GroupList sharedGroupList] insertGroup:movedGroup atIndex:toIndex]; // Update the loadedGroupIndex pointer if (loadedGroupIndex < fromIndex & loadedGroupIndex >= toIndex) { loadedGroupIndex = loadedGroupIndex + 1; } else if (loadedGroupIndex > fromIndex & loadedGroupIndex < toIndex) { loadedGroupIndex = loadedGroupIndex - 1; } else if (loadedGroupIndex == fromIndex) { loadedGroupIndex = toIndex; } [movedGroup release]

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  • Is calling of overload operator-> resolved at compile time?

    - by Brent
    when I tried to compile the code: (note: func and func2 is not typo) struct S { void func2() {} }; class O { public: inline S* operator->() const; private: S* ses; }; inline S* O::operator->() const { return ses; } int main() { O object; object->func(); return 0; } there is a compile error reported: D:\code>g++ operatorp.cpp -S -o operatorp.exe operatorp.cpp: In function `int main()': operatorp.cpp:27: error: 'struct S' has no member named 'func' it seems that invoke the overloaded function of "operator-" is done during compile time? I'd added "-S" option for compile only.

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  • Compatible types and structures in C

    - by Oli Charlesworth
    I have the following code: int main(void) { struct { int x; } a, b; struct { int x; } c; struct { int x; } *p; b = a; /* OK */ c = a; /* Doesn't work */ p = &a; /* Doesn't work */ return 0; } which fails to compile under GCC (3.4.6), with the following error: test.c:8: error: incompatible types in assignment test.c:9: warning: assignment from incompatible pointer type Now, from what I understand (admittedly from the C99 standard), is that a and c should be compatible types, as they fulfill all the criteria in section 6.2.7, paragraph 1. I've tried compiling with std=c99, to no avail. Presumably my interpretation of the standard is wrong?

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  • handling activity destruction in multithreaded android app

    - by Jayesh
    Hi, I have a multithreded app where background threads are used to load data over network or from disk/db. Every once in a while user will perform some action e.g. fetch news over network, which will spawn a background AsyncTask, but for some reason user will quit the app (press back button so that activity gets destroyed). In most such scenarios, I make appropriate checks in the background thread after it returns from n/w i/o, so that it won't crash by accessing members of the activity that is destroyed by now. However some corner cases are left where crashes happen, because the background thread would access some member of activity that is now null. Do other Android developers have some generic/recommended framework to handle such scenarios? These are the times when I wish android would have guaranteed termination of all threads when activity destroys (in the same way that regular linux process cleans up when it's quit)... but I guess Android devs had good reasons for not exposing process lifetimes through the api.

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  • Can any function be a deleted-function?

    - by Caspin
    The working draft explicitly calls out that defaulted-functions must be special member functions (eg copy-constructor, default-constructor, etc). Which makes perfect sense. However, I don't see any such restriction on deleted-functions. Is that right? Or in other words are these three examples valid c++0? struct Foo { // 1 int bar( int ) = delete; }; // 2 int baz( int ) = delete; template< typename T > int boo( T t ); // 3 template<> int boo<int>(int t) = delete;

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  • Drupal: Programmatically saving imagefield images

    - by Ace
    Hey there! I'm trying to write a sync function that saves some data to nodes, which works fine, until I try to save the thumbnail image associated with the node. I've managed to download the file and put it in my sites/default/files folder, but what's the best way to tell Drupal, "put this file in that CCK imagefield"? EDIT To clarify a bit.. I sync the thumbnails separately (since one image can be used by several nodes)... I would like the initial thumbnail sync to save the files in the correct folder (not a temp one) and just point the imagefield to this file... That's what annoys me with field_file_save_file(), it saves a new file instead of just making a pointer.. Any advice?

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  • How to implement User base security not role base in asp.net?

    - by Gaurav
    Hi, I have to implement User base security in my Web project using .Net3.5. Followings are some we need: Roles can be Admin, Manage, Editor, Member etc User can have multiple roles Every roles has its own dynamic menus and restrictions/resources All menus and interface will populate dynamically from Database I heard some where this kind of i.e user base security can be implemented using HashTable but I dont know how is it? Today I came to know that for this kind of work Java people use Interceptor Design patterns. So, how could I do the same in asp.net C#?

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  • where are wrong in my php code ????

    - by user318068
    hi all, <td align="center" bgcolor="#FFFFFF"><?php echo '<label onclick="window.open('profilephp.php?member=$row['MemberID']','mywindow')">'.{$row['MemberName']}.'</label>';?><br /> <?php echo "<p align='center'><img width='100' height='100' src={$row['MemberImg']} alt='' /></p>";?></td></tr> Parse error: syntax error, unexpected T_STRING, expecting ',' or ';' in C:\xampp\htdocs\home - Copy\membercopy.php on line 141 I really don't know where it went wrong. Please help,

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  • Handle/Grip bar convention

    - by tomdemuyt
    Greetings, Because textarea elements do not resize with jquery.touch ( http://plugins.jquery.com/project/touch ), I've put an textarea in a table where the first row allows the user to drag the table around and resize it with the textarea growing/shrinking/moving along. It works well, except that users dont seem to 'get' that they can use the bar to resize/move. I was trying to find some 'grip bar' graphics but google isnt helping me. What is the best way to show users that an element can be moved/resized ? Pointer to graphics ( generators ) would be great. Or, does any one know how to make textarea's movable/resizable ? T.

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  • How to do Linq aggregates when there might be an empty set?

    - by Shaul
    I have a Linq collection of Things, where Thing has an Amount (decimal) property. I'm trying to do an aggregate on this for a certain subset of Things: var total = myThings.Sum(t => t.Amount); and that works nicely. But then I added a condition that left me with no Things in the result: var total = myThings.Where(t => t.OtherProperty == 123).Sum(t => t.Amount); And instead of getting total = 0 or null, I get an error: System.InvalidOperationException: The null value cannot be assigned to a member with type System.Decimal which is a non-nullable value type. That is really nasty, because I didn't expect that behavior. I would have expected total to be zero, maybe null - but certainly not to throw an exception! What am I doing wrong? What's the workaround/fix?

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  • status failed for LdrLoadDll

    - by kiddo
    hello all,I'am trying to work-out the LdrLoadDll function and am having no luck with that..i also googled for some examples there is no much documentation or correct example about this.I know what it exactly does..Please check the code below. //declaration function pointer for LdrLoadDll typedef NTSTATUS (_stdcall*fp_LdrLoadDll)( IN PWCHAR PathToFile OPTIONAL, IN ULONG Flags OPTIONAL, IN PUNICODE_STRING ModuleFileName, OUT PHANDLE ModuleHandle ); //calling LdrLoadDll using getprocaddress HANDLE handle; HMODULE module = LoadLibrary(L"ntdll.dll"); fp_LdrLoadDll loadDll; loadDll = (fp_LdrLoadDll)GetProcAddress(module,"LdrLoadDll"); if(loadDll == NULL) { MessageBox(0,L"Not able to load the function",L"LdrLoadDll",&handle); } UNICODE_STRING input; input.Buffer = L"C:\\Desktop\\myDll.dll"; input.Length = wcslen(input.Buffer)*2; input.MaximumLength = wcslen(input.Buffer) +2; NTSTATUS status = loadDll(NULL,LOAD_WITH_ALTERED_SEARCH_PATH,&input,0); When i execute the above am not getting the handle niether valid status.Please help me with this.

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  • Why does a delegate with no parameters compile?

    - by Ryan
    I'm confused why this compiles: private delegate int MyDelegate(int p1, int p2); private void testDelegate() { MyDelegate imp = delegate { return 1; }; } MyDelegate should be a pointer to a method that takes two int parameters and returns another int, right? Why am I allowed to assign a method that takes no parameters? Interestingly, these doesn't compile (it complains about the signature mismatches, as I'd expect) private void testDelegate() { // Missing param MyDelegate imp = delegate(int p1) { return 1; }; // Wrong return type MyDelegate imp2 = delegate(int p1, int p2) { return "String"; }; } Thanks for any help! Ryan

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  • What's void *userData exactly?

    - by mystify
    In a C function declaration, I have seen this parameter definition: void *userData so, what exactly is that? My guess: the void says it can be anything arbitrary, or even nothing. Almost similar to id of objective-c. It just allows to pass in whatever data structure you like. The star in front of userData says, that the argument must be passed in by reference. So when using this stuff in the function body, typically it must be casted and dereferenced. So if I pass in an pointer to SomeClass instance, I would get that like this: SomeClass *myObj = (SomeClass*)userData; In the case I had nothing special to pass along, I would provide NULL as argument. Are my assumptions correct? Or did I get something wrong?

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  • Java JPA @OneToMany neededs to reciprocate @ManyToOne?

    - by bguiz
    Create Table A ( ID varchar(8), Primary Key(ID) ); Create Table B ( ID varchar(8), A_ID varchar(8), Primary Key(ID), Foreign Key(A_ID) References A(ID) ); Given that I have created two tables using the SQL statements above, and I want to create Entity classes for them, for the class B, I have these member attributes: @Id @Column(name = "ID", nullable = false, length = 8) private String id; @JoinColumn(name = "A_ID", referencedColumnName = "ID", nullable = false) @ManyToOne(optional = false) private A AId; In class A, do I need to reciprocate the many-to-one relationship? @Id @Column(name = "ID", nullable = false, length = 8) private String id; @OneToMany(cascade = CascadeType.ALL, mappedBy = "AId") private List<B> BList; //<-- Is this attribute necessary? Is it a necessary or a good idea to have a reciprocal @OneToMany for the @ManyToOne? If I make the design decision to leave out the @OneToMany annotated attribute now, will come back to bite me further down.

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  • Reading in 4 bytes at a time

    - by alphomega
    I have a big file full of integers that I'm loading in. I've just started using C++, and I'm trying out the filestream stuff. From everything I've read, it appears I can only read in bytes, So I've had to set up a char array, and then cast it as a int pointer. Is there a way I can read in 4 bytes at a time, and eliminate the need for the char array? const int HRSIZE = 129951336; //The size of the table char bhr[HRSIZE]; //The table int *dwhr; int main() { ifstream fstr; /* load the handranks.dat file */ std::cout << "Loading table.dat...\n"; fstr.open("table.dat"); fstr.read(bhr, HRSIZE); fstr.close(); dwhr = (int *) bhr; }

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  • Need help with events in COM in pure C++!

    - by Artem
    Hello, guys! Very important question: Please, look at my project (300Kb). I can`t use MFC/ATL, pure C++ only. I have COM library (niapi.dll), but no sources/headers available, dll only. There is class for connecting to server (NiApi::SrvrSession), class has login event handler (NiApi::SrvrSession::OnLogin). I used #import "NiApi.dll" to generate wrappers/information, then ISrvrSessionPtr session(L"NiApi.SrvrSession"); to create object, then trying session->put_OnLogin(); to assign events, but there is no one put_On or such member. niapi.tlh have _ISrvrSessionEvents struct inside, but it have no relations with SrvrSession. I need to use events from NiApi::SrvrSession for handling connection status. Please help or my boss kill me! (sorry for broken english, I read better than speak;)

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  • Parent-Child relation while using object data source

    - by Saba
    Hello guys I am experiencing with a class generator I've written, which generates a class for each table in database with each table field as a property and such. Before that, I used to add a typed dataset to the project and add some tables to it. It automatically detected the relationship between tables and when I added a parent table as data source of a datagrid, I could add another datagrid and use the foreing key data member of it's bindingsource to fill it, and when someone moved the focus on parent datagrid, the data in child datagrid would change accordingly. Now that I have my classes, I add an object as data source for my 2 datagrids, but obviously it doesn't detect a parent child relation. But It'd really help if I could have that foreign key relation in my object datasources. Is there any way to have that relation in object datasource?

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  • Eager loading in EF1.0

    - by Dave Swersky
    I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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  • Double indirection and structures passed into a function

    - by ZPS
    I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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  • Objective C LValue required as unary '&' operand

    - by Bob
    Hello! In my code, I get this error when I try to get a pointer to my class property. (I wrote a small *.OBJ file translator in Python, discarding the normals) CODE: //line: line of text const char *str = [line UTF8String]; Point3D *p1, *p2, *p3; p1 = [Point3D makeX:0 Y:0 Z:0]; p2 = [Point3D makeX:0 Y:0 Z:0]; p3 = [Point3D makeX:0 Y:0 Z:0]; sscanf(str, "t %f,%f,%f %f,%f,%f %f,%f,%f",(&[p1 x]),&([p1 y]),&([p1 z]),&([p2 x]),&([p2 y]),&([p2 z]),&([p3 x]),&([p3 y]),&([p3 z])); Triangle3D *tri = [Triangle3D make:p1 p2:p2 p3:p3];

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