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  • Strange pattern matching with functions instancing Show

    - by Sean D
    So I'm writing a program which returns a procedure for some given arithmetic problem, so I wanted to instance a couple of functions to Show so that I can print the same expression I evaluate when I test. The trouble is that the given code matches (-) to the first line when it should fall to the second. {-# OPTIONS_GHC -XFlexibleInstances #-} instance Show (t -> t-> t) where show (+) = "plus" show (-) = "minus" main = print [(+),(-)] returns [plus,plus] Am I just committing a motal sin printing functions in the first place or is there some way I can get it to match properly? edit:I realise I am getting the following warning: Warning: Pattern match(es) are overlapped In the definition of `show': show - = ... I still don't know why it overlaps, or how to stop it.

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  • Linq - reuse expression on child property

    - by user175528
    Not sure if what I am trying is possible or not, but I'd like to reuse a linq expression on an objects parent property. With the given classes: class Parent { int Id { get; set; } IList<Child> Children { get; set; } string Name { get; set; } } class Child{ int Id { get; set; } Parent Dad { get; set; } string Name { get; set; } } If i then have a helper Expression<Func<Parent,bool> ParentQuery() { Expression<Func<Parent,bool> q = p => p.Name=="foo"; } I then want to use this when querying data out for a child, along the lines of: using(var context=new Entities.Context) { var data=context.Child.Where(c => c.Name=="bar" && c.Dad.Where(ParentQuery)); } I know I can do that on child collections: using(var context=new Entities.Context) { var data=context.Parent.Where(p => p.Name=="foo" && p.Childen.Where(childQuery)); } but cant see any way to do this on a property that isnt a collection. This is just a simplified example, actually the ParentQuery will be more complex and I want to avoid having this repeated in multiple places as rather than just having 2 layers I'll have closer to 5 or 6, but all of them will need to reference the parent query to ensure security.

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  • How to create a function and pass in variable length argument list?

    - by Jian Lin
    We can create a function p in the following code: var p = function() { }; if (typeof(console) != 'undefined' && console.log) { p = function() { console.log(arguments); }; } but the arguments are passed like an array to console.log, instead of passed one by one as in console.log(arguments[0], arguments[1], arguments[2], ... Is there a way to expand the arguments and pass to console.log like the way above? Note that if the original code were var p = function() { }; if (typeof(console) != 'undefined' && console.log) { p = console.log; } then it works well on Firefox and IE 8 but not on Chrome.

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  • Do mini-filter functions need APCs enabled?

    - by botismarius
    Hello, Many Zw* functions that work with files (such as ZwCreateFile) need to be called at PASSIVE_LEVEL with APCs enabled: http://msdn.microsoft.com/en-us/library/ff566424%28VS.85%29.aspx. This is because, internally, I/O operations are asynchronously and the completion of an operation is delivered through an APC (correct me if I'm wrong). However, the documentation for similar functions from a mini-filter (such as FltCreateFile, FltReadFile, etc) does not specify that APCs should be enabled. Is it safe to call FltCreateFile/FltReadFile with APCs disabled? Thanks!

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  • calling two functions sequentially in vbscript with single click event

    - by sushant
    i need to call two function on a single click event. and also the functions shud get executed sequentially. i tried click me . but its not working.its not calling any of the functions. here is the complete code. sorry for formatting. function copy() Dim WshShell, oExec,g,h h="D:\d" g="xcopy " & h & " " & "D:\y\ /E" Set WshShell = CreateObject("WScript.Shell") Set oExec = WshShell.Exec(g) Do While oExec.Status = 0 WScript.Sleep 100 Loop WScript.Echo oExec.Status end function function zip() Dim WshShel, oExe Set WshShel = CreateObject("WScript.Shell") Set oExe = WshShel.Exec("cmd /c cd D:\d & D: & winzip32.exe -min -a D:\a") Do While oExe.Status = 0 WScript.Sleep 100 Loop WScript.Echo oExe.Status end function click me any help is appreciated.

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  • Filtering two arrays to avoid Inf/NaN values

    - by Gacek
    I have two arrays of doubles of the same size, containg X and Y values for some plots. I need to create some kind of protection against Inf/NaN values. I need to find all that pairs of values (X, Y) for which both, X and Y are not Inf nor NaN If I have one array, I can do it using lambdas: var filteredValues = someValues.Where(d=> !(double.IsNaN(d) || double.IsInfinity(d))).ToList(); Now, for two arrays I use following loop: List<double> filteredX=new List<double>(); List<double> filteredX=new List<double>(); for(int i=0;i<XValues.Count;i++) { if(!double.IsNan(XValues[i]) && !double.IsInfinity(XValues[i]) && !double.IsNan(YValues[i]) && !double.IsInfinity(YValues[i]) ) { filteredX.Add(XValues[i]); filteredY.Add(YValues[i]); } } Is there any way of filtering two arrays at the same time using LINQ/Lambdas, as it was done for single array?

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  • Best practice for error handling in codeigniter / php apps

    - by Industrial
    Hi everyone, We're working with a new codeigniter based application that are cross referencing different PHP functions forwards and backwards from various libraries, models and such. We're running PHP5 on the server and we try to find a good way for managing errors and status reports that arises from the usage of our functions. While using return in functions, the execution is ended, so nothing more can be sent back. Right? What's the best practice to send a status information or error code upon ending execution of actual function? Should we look into using exceptions or any other approach? http://us.php.net/manual/en/language.exceptions.php

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  • boost.asio's socket's recieve/send functions are bad?

    - by the_drow
    Data may be read from or written to a connected TCP socket using the receive(), async_receive(), send() or async_send() member functions. However, as these could result in short writes or reads, an application will typically use the following operations instead: read(), async_read(), write() and async_write(). I don't really understand that remark as read(), async_read(), write() and async_write() can also end up in short writes or reads, right? Why are those functions not the same? Should I use them at all? Can someone clarify that remark for me?

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  • Problem with default member functions of class in C++ (constructor, destructor, operator=, copy cons

    - by Narek
    We know that compiler generates some member functions for user-defined class if that member functions are not defined but used, isn't it. So I have this kind of code: class AA { }; void main() { AA a; AA b(a); a = b; } This code works fine. I mean no compiler error. But the following code.... class AA { int member1; int member2; }; But this code gives an run time error, because variable "a" is used without being iniltialized!!! So my question is this: when we instantiate an int, it has a value. So why the default constructer doesn't work and by using those two int numbers initializes variable "a"??

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  • Using a message class static method taking in an action to wrap Try/Catch

    - by Chris Marisic
    I have a Result object that lets me pass around a List of event messages and I can check whether an action was successful or not. I've realized I've written this code in alot of places Result result; try { //Do Something ... //New result is automatically a success for not having any errors in it result = new Result(); } catch (Exception exception) { //Extension method that returns a Result from the exception result = exception.ToResult(); } if(result.Success) .... What I'm considering is replacing this usage with public static Result CatchException(Action action) { try { action(); return new Result(); } catch (Exception exception) { return exception.ToResult(); } } And then use it like var result = Result.CatchException(() => _model.Save(something)); Does anyone feel there's anything wrong with this or that I'm trading reusability for obscurity?

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  • OBject access from different functions in VC++

    - by sijith
    Hi, I have 3 function in my class B. These three function have to access member function of other class A. I did this by creating object of class A in class B constructor and tried to access that object in functions of class B. But its showing error. How can i assess the same object in these three functions. Where i have to create object of class A B::B() { A a; } B:: function() { a.fun(); //fun belongs to class A } B:: function1() { a.fun1(); //fun1 belongs to class A } I am getting error, How can i implement the same where i can access object a in both function.

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  • Linkage of namespace functions

    - by user144182
    I have a couple of methods declared at the namespace level within a header for a class: // MyClass.h namespace network { int Method1(double d); int Method2(double d); class MyClass { //... } } then defined in //MyClass.cpp int Method1(double d) { ... } int Method2(double d) { ... } This project compiles cleanly and is a dependency for a ui project which uses MyClass. The functions were previously member functions of MyClass, but were moved to namespace since it was more appropriate. My problem is the ui project complains when it gets to the linker: 1network.lib(MyClass.obj) : error LNK2001: unresolved external symbol "int __cdecl network::Method1(double)" (?INT@ds@sim@@YAHN@Z) 1network.lib(MyClass.obj) : error LNK2001: unresolved external symbol "int __cdecl network::Method2(double)" (?CINT@ds@sim@@YAHN@Z) What am I doing wrong?

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  • How to write this in better way?

    - by dario
    Hi all. Let's look at this code: IList<IHouseAnnouncement> list = new List<IHouseAnnouncement>(); var table = adapter.GetData(); //get data from repository object -> DataTable if (table.Rows.Count >= 1) { for (int i = 0; i < table.Rows.Count-1; i++) { var anno = new HouseAnnouncement(); anno.Area = float.Parse(table.Rows[i][table.powierzchniaColumn].ToString()); anno.City = table.Rows[i][table.miastoColumn].ToString(); list.Add(anno); } } return list; Is it better way to write this in less code and better fashion (must be :-) )? Maybe using labda (but let mi know how)? Thanks in advance!

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  • View Lambdas in Visual Studio Debugger

    - by Vaccano
    I have the a simple LinqToSQL statement that is not working. Something Like this: List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false) .ToList(); I look at _ctx.DBList in the debugger and the second item fits both parameters. Is there a way I can dig into this more to see what is going wrong?

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  • Reference to an instance method of a particular object

    - by Andrey
    In the following code, if i try to pass method reference using the class name, works. But passing the reference variable compiler gives an error, i do not understand why? public class User { private String name; public User(String name) { this.name = name; } public void printName() { System.out.println(name); } } public class Main { public static void main(String[] args) { User u1 = new User("AAA"); User u2 = new User("BBB"); User u3 = new User("ZZZ"); List<User> userList = Arrays.asList(u1, u2, u3); userList.forEach(User::printName); // works userList.forEach(u1::printName); // compile error } } Thanks,

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  • javascript: what are immediate functions used for [duplicate]

    - by tkoomzaaskz
    This question already has an answer here: Why using self executing function in JavaScript? [duplicate] 4 answers I've been programming in JS since some time, but I have never came upon a need of using immediate functions, for example: (function(){ console.log('hello, I am an immediate function'); }()) What would be the difference if I just wrote: console.log('hello, I am an immediate function'); ? I don't have any access to this function anyway (it is not assigned anywhere). I think (but I'm not sure) that I can implement everything without immediate functions - so why do people use it?

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  • PHP: Classes to use functions from each other?

    - by Martti Laine
    Hello I've been into this problem for a while already, and have asked some questions about it here Stackoverflow. I've got some advice, but I just can't understand it. Could someone provide me an example of classes working smoothly together. I have 3 (maybe more) classes: mysql user alerts As I said, could someone provide an example, so these classes could use functions from each other class, e.g. user could use mysql's functions. I'm asking for an simple example, for learning-purposes. And please, no google-suggestions or links to other questions. I've tried to search this for a while already. No success, though. Martti Laine

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  • How to select a single object using Linq in vb.net

    - by Hucker
    I have done a lot of searching to what appears to be a simple LINQ problem but I can't figure out how to do grab an object out of a collection that has a specified minimum (or max value) without resorting to a sort like this: > dim customers= GetCustomers() > > dim youngest = (From c in customers > Order By c.age Ascending).ToList.First This (untested code) structure works fine with the exception that the entire customer array must be sorted and placed into a list for the only purpose of extracting the first value. That can't be the best way to get the minimum! Note that I want the whole c record in this case, not the minumum age of a customer that can be done like this (a typical example): > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c.age).Min Or even > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c).Min(Function(x) x.age) I can't for the life of me figure out how to get the whole object (or even the index) without resorting to the sort...

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  • list all functions on CRAN

    - by baptiste
    Suppose I'm trying to run a script of unknown origin, and one of the functions is from a package that is not loaded by the script (an oversight, maybe it was loaded in the .Rprofile of the person who wrote it). How can I find in which package this function resides? There's some information compiled on CRAN, that doesn't require the user to download/install all R packages locally; however as far as I could tell it only gives access to the DESCRIPTION files. RSiteSearch, and its web equivalent, seem to access an online database of all CRAN packages, where presumably a list of all functions would be available. Is there some way of accessing this information? Thanks. Edit: I know sos::findFn, utils::RSiteSearch and search.r-project; what I would like is to get the raw data that these tools use.

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  • const member functions can call const member functions only?

    - by Abhi
    Hi all. Do const member functions call only const member functions? class Transmitter{ const static string msg; mutable int size; public: void xmit() const{ size = compute(); cout<<msg; } private: int compute() const{return 5;} }; string const Transmitter::msg = "beep"; int main(){ Transmitter t; t.xmit(); return EXIT_SUCCESS; } If i dont make compute() a const, then the compiler complains. Is it because since a const member function is not allowed to modify members, it wont allow any calls to non-consts since it would mean that the const member function would be 'indirectly' modifying the data members?

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  • Single C++/CLI method to wrap many type specific C functions

    - by T33C
    I am wrapping a C library using C++/CLI so that the C library can be used easily from C# in a C#'ish way. Some of the functions in this library are for putting a value into a container. There are no generics in C so there exists a function per type CLIB_SetBool(BOOL value), CLIB_SetInt(int value), CLIB_SetString(char* string) and so on. To make it easier to use from C#, I have created a single Set function which takes a System::Object. I have two related questions: With my method how would you use a switch statement on the type of System::Object to call the correct CLIB_Setxxxx function. [typeid is only for unmanaged code and I can't seem to use GetType.] Is there a better way to wrap these functions like using a Generic? [I started using template specialisation but then realised that C# doesn't see templates.] Thanks.

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