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  • Direct flow depending on incoming dynamic type

    - by Improfane
    I have a listener class that accepts GUI change events in one method. The incoming event objects have a superclass of a type of GUI Event, the behaviour should depend on the dynamic type of the incoming variable. I wanted to do do lots of methods like: handleGUIEvent(EventChangedX event) handleGUIEvent(EventChangedY event) I am using a single event listener and receiving objects of various types but the behaviour should be different for each. What would you do? I do not want to use a switch statement as this would get unmaintainable.

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  • question about c++ template functions taking any type as long that type meets at least one of the re

    - by smerlin
    Since i cant explain this very well, i will start with a small example right away: template <class T> void Print(const T& t){t.print1();} template <class T> void Print(const T& t){t.print2();} This does not compile: error C2995: 'void Print(const T &)' : function template has already been defined So, how can i create a template function which takes any type T as long as that type has a print1 memberfunction OR a print2 memberfunction (no polymorphism) ?

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  • Cannot implicitly convert type 'char*' to 'bool'

    - by neeraj
    i was trying to passing pointer value in the function , i really got stuck here I am a beginner , not getting what value should be put this is programme from the reference of the book "Cracking the coding interview " By Gayle Laakmann McDowell, class Program { unsafe void reverse(char *str) { char* end = str; char tmp; if (str) //Cannot implicitly convert type 'char*' to 'bool' { while(*end) //Cannot implicitly convert type 'char*' to 'bool' { ++end; } --end; while(str<end) { tmp = *str; *str+= *end; *end-= tmp; } } } public static void Main(string[] args) { } }

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  • Does "Value Restriction" practically mean that there is no higher order functional programming?

    - by Sadache
    Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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  • Linq to SQl Stored Procedure Problem( it can't figure out the return type)

    - by chobo2
    Hi I have this SP USE [Test] GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE PROCEDURE [dbo].[UsersInsert](@UpdatedProdData XML) AS INSERT INTO dbo.UserTable(UserId,UserName,LicenseId,Password,PasswordSalt,Email,IsApproved,IsLockedOut,CreateDate, LastLoginDate,LastLockOutDate,FailedPasswordAttempts,RoleId) SELECT @UpdatedProdData.value('(/ArrayOfUsers/Users/UserId)[1]', 'uniqueidentifier'), @UpdatedProdData.value('(/ArrayOfUsers/Users/UserName)[1]', 'varchar(20)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LicenseId)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Password)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/PasswordSalt)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Email)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsApproved)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsLockedOut)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/CreateDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLoginDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLockOutDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/FailedPasswordAttempts)[1]', 'int'), @UpdatedProdData.value('(/ArrayOfUsers/Users/RoleId)[1]', 'int') Now this SP creates just fine. It's when I go to VS2010 and try to drag this SP in my method panel of my linq to sql file in design view. It tells me that it can't figure out the return type. I try to go to the properties but it does not have "none" as a choice and I can't type it in. It should be "none" so how do I set it to "none"?

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  • Using module include in OCaml

    - by Geoff
    In OCaml 3.11, I want to "extend" an existing module using the include directive, like so: module MyString = struct include String let trim s = ... end No problem. But now I want to expose this module's type explicitly (i.e. in a .mli file). I want something like this: module MyString : sig include String val trim : string -> string end But the include syntax is not correct because String refers to a module, not a module type (and the compiler does indeed barf). How can I refer to the module type for String here (without having write it out explicitly in a sig expression)? Thanks!

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  • Is there a way to localize input type="date" in HTML5

    - by lambacck
    I know that at the time of this writing only Opera supports a browser UI for <input type="date" name="mydate"> and maybe my attempts to localize this field have been met with frustration because niceties like localization have not yet been included in their implementation, but I don't even see mention of it in the HTML5 spec. Is there a way that localization should be specified? Should I do lang="fr" on a parent element? Some notes on the implementation of the site in question: Localization (language) is explicitly picked by the user because they are managing data in multiple languages and it is not reasonable to expect that the user's browser chrome is in the language being viewed or that the browser is providing desired language request headers. I want to be sure that if the page is rendered in French that the date picker provided by browser chrome shows options that make sense for French language. The plan is to fall back to jQueryUI for browsers that do not support type="date", I will use the detection mechanism provided in Dive into HTML 5

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  • Using NSArray for C-type int comparisons

    - by Andrew Barinov
    I would like to iterate through an NSArray of ints and compare each one to a specific int. All ints are C type ints. The code I am using is as follows: -(int)ladderCalc: (NSArray*)amounts: (int)amount { int result; for (NSUInteger i=0; i< [amounts count]; i++) { if (amount < [amounts objectAtIndex:i]); { // do something } // do something } } However I get an error when comparing the int amount to the result of [amounts objectAtIndex:i] because you cannot compare id to int. Why is the id involved in this case? Shouldn't objectAtIndex just return the object at the index specified? Is it possible to cast the object returned to an C int and then do the comparison? Or should I just dispense with NSArray and do this type of thing in C?

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  • Overloading on return type ???

    - by Green Hyena
    scala> val shares = Map("Apple" -> 23, "MicroSoft" -> 50, "IBM" -> 17) shares: scala.collection.immutable.Map[java.lang.String,Int] = Map(Apple -> 23, MicroSoft -> 50, IBM -> 17) scala> val shareholders = shares map {_._1} shareholders: scala.collection.immutable.Iterable[java.lang.String] = List(Apple, MicroSoft, IBM) scala> val newShares = shares map {case(k, v) => (k, 1.5 * v)} newShares: scala.collection.immutable.Map[java.lang.String,Double] = Map(Apple -> 34.5, MicroSoft -> 75.0, IBM -> 25.5) From this example it seems like the map method is overloaded on return type. Overloading on return type is not possible right? Would somebody please explain what's going on here?

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  • How to handle ViewData type casting in MVC

    - by Wondering
    Hi All, I am new to MVC and facing one issue. I have a xml file and i am retrieving its value using Linq to xml and assigning it to ViewData. Controller.cs var res=from x in doc.Descendants("person") select new { Fname=x.Element("fname").Value, Lname=x.Element("lname").Value }; ViewData["Persons"]=res; in View I am trying <% foreach (var item in ViewData["Persons"]) { %> <li> <%= item.Fname %> </li> <% } %> but foreach (var item in ViewData["Persons"] is giving type casting error..what should be the exact type csting so that i can retrive values in the format item.Fname. Thanks.

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  • Problem when trying to define Show for my Point3D type in Haskell

    - by devoured elysium
    I am trying to define Show for my Point3D type: type Point3D = (Integer, Integer, Integer) instance Show Point3D where show (x,y,z) = "<" ++ (show x) ++ "," ++ (show y) ++ "," ++ (show z) ++ ">" yet I must be missing something in the sintax, as I am always getting an error: Illegal instance declaration for `Show Point3D' (All instance types must be of the form (T t1 ... tn) where T is not a synonym. Use -XTypeSynonymInstances if you want to disable this.) In the instance declaration for `Show Point3D' What am I doing wrong?

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  • Collection type generated by for with yield

    - by Jesper
    When I evaluate a for in Scala, I get an immutable IndexedSeq (a collection with array-like performance characteristics, such as efficient random access): scala> val s = for (i <- 0 to 9) yield math.random + i s: scala.collection.immutable.IndexedSeq[Double] = Vector(0.6127056766832756, 1.7137598183155291, ... Does a for with a yield always return an IndexedSeq, or can it also return some other type of collection class (a LinearSeq, for example)? If it can also return something else, then what determines the return type, and how can I influence it? I'm using Scala 2.8.0.RC3.

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  • Declaring a data type dynamically in C++

    - by Bobby
    I want to be able to do the following: I have an array of strings that contain data types: string DataTypeValues[20] = {"char", "unsigned char", "short", "int"}; Then later, I would like to create a variable of one of the data types at runtime. I won't know at compile time what the correct data type should be. So for example, if at runtime I determined a variable x needed to be of type int: DataTypeValues[3] x = 100; Obviously this won't work, so how could I do something like this?

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  • problems with Haskell's Number Types

    - by mindeavor.
    I have the following haskell code: fac n = product [1..n] taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h where hp i = h^i / fac i w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0 taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25 where f t x = t^4 - 4*x/t f' t x = 4*t^3 - 4*(f t x)/t + 4*x/t^2 f'' t x = 12*t^2 - 4*(f' t x)/t + 8*(f t x)/t^2 - 8*x/t^3 taylor_results is supposed to be a use case of taylor3s. However, there is something wrong with the number type inferencing. When I try to compile, this is the error I get: practice.hs:93:26: Ambiguous type variable `a' in the constraints: `Integral a' arising from a use of `taylor3s' at practice.hs:93:26-51 `Fractional a' arising from a use of `f' at practice.hs:93:37 Possible cause: the monomorphism restriction applied to the following: taylor_results :: [a] (bound at practice.hs:93:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Can someone help me with understanding what the problem is?

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  • How to detect if a form input element of type file is empty

    - by Ankur
    I have some code which reads a file through a form field of type file <input type="file" ... /> I want to give the user another option of providing a url to a file rather than having to upload it as many are already online. How can I detect when this field is empty on the server side. I am using Apache Commons FileUpload FileItemStream item = iter.next(); name = item.getFieldName(); stream = item.openStream(); if(!item.isFormField()){ if(item.toString()!=""){ .... I need to detect when item is empty. The above code doesn't work, nor does using: if(item.equals(null)){ ....

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  • How to know any request type with comet in tomcat 6

    - by Alvin
    Hi, I want to create a chat application in Tomcat 6.0, but before allowing any user for chatting I want to authenticate a user or registering its account to the database by passing request to the servlets at the comet Event type Begin. But I don't know how to know about the request type. How can I know a user has already been logged in, or he is making a request for registering his account. How can I know this by implementing CometProcessor interface? Is there any better way to do that task?

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  • data type trouble in php

    - by user225269
    I don't know why but the data type in this code makes a trouble when the id in the url starts with the number zero like this: http://localhost/exp/update.php?id=03A43 In this case the id is 03A43. And my query looks like this: mysql_select_db("school", $con); $result = mysql_query("SELECT * FROM student WHERE IDNO=".(int)$_GET['id']); ?> There is no problem in the design if the id does not start with the number zero. What might be the proper data type for numbers beginning in zero?

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  • Java Sql Udate error, data type missmatch

    - by codo
    I have created a table in ms access. I have set the data type of ID to Auto Number in MS-access. In java when I try to update a record. the netBeans IDE gives me the error of " data type missmatch in criteria expression". But when I changed the ID number that was not in the table already it works well. The code is below. String sql = "Update table1 set price ='" + txtPrice.getText() + "', quantity='" + txtQuantity.getText() + "', description='" + txtDescription.getText() + "' where id= " + txtid.getText() + ""; try { pst = conn.prepareStatement(sql); pst.executeUpdate(); JOptionPane.showMessageDialog(null, "Updated"); UpdateJTable(); } catch (Exception e) { JOptionPane.showMessageDialog(null, e); }

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  • using AutoCompleteTextField in wicket without String as the generic type

    - by Manuel
    Hi! This question follows this: handling to onchange event of AutoCompleteTextField in wicket I'm trying to use the AutoCompleteTextField with a custom class as the generic type, and to add an AjaxFormComponentUpdatingBehavior. What I mean is I want to have a AutoCompleteTextField<SomeClass> myAutoComplete = ...; and after that add a AjaxFormComponentUpdatingBehavior: myAutoComplete.add(new AjaxFormComponentUpdatingBehavior("onchange") { @Override protected void onUpdate(AjaxRequestTarget target) { System.out.println( "Value: "+getValue() ); } }); The problem is that for some reason, adding that behavior makes the form try to set the model object with a String (even though the AutoCompleteTextField has a generic type of SomeClass), causing a ClassCastException when the onchange event fires. Is there a way to use AutoCompleteTextField without it being AutoCompleteTextField<String>? I couldn't find any example. Thanks for your time! and thanks to the user biziclop for his help in this matter.

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  • Sending JSON content type in from JavaScript objects ( jQuery ajax )

    - by smartnut007
    I am having trouble sending JavaScript objects as a http request that only accepts json content-type. i.e "application/json" or "text/json" But, I am not sure why data2 ( stringified json ) works fine But, data1 ( json object ) does throws 400 ( Bad Request ). i.e I am not sure jQuery does not serialize the json object to a valid json string for the server to process. var data1 = ({ rating : 3 }); //does not work var data2 = '{ "rating" : 3}'; //works fine $.ajax({ url : "/rate", data : data1, type : "POST", contentType: "application/json", success: function(json){ console.log("Ajax Return :"+json); } });

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  • Parent key of type encoded string?

    - by user246114
    Hi, How do we create a parent key which is an encoded string? Example: class Parent { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String mEncKey; } class Child { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String mEncKey; // In the doc examples, they have Key as the type here. @Persistent @Extension(vendorName="datanucleus", key="gae.parent-pk", value="true") private String mParentEncKey; } yeah I'm not sure how to make mParentEncKey an encoded string type, because the 'key' label is already being used? I would need something like?: key="gae.parent-pk.encoded-pk" not sure - is that possible? Thanks

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  • PHP find if file data is an image

    - by Christian Sciberras
    Imagine I have some file data in a variable $data. I need to determine whether it is an image or not. No need for details such as corrupt images etc. Firs thought would be getting the file mime type by looking at the magic number and then see whether "image" is in the mime type. No such luck, even if I have a "file extension to mime type" script, I don't have a reliable way to get mime from magic number. My next option was to have a reasonable list of image file magic numbers and consult them. However, it relatively difficult to find such magic numbers (gif for instance has different magic numbers, some of which could pretty rare - if memory serves me right). A better idea would be some linux program which can do this kind of thing. Any ideas? I'm running RHEL and PHP 5.3. I've got root access - ie able to install stuff if needed. - Chris.

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  • How to change a vairable type in C#?

    - by Mosho Mulan
    I wanted to use something like this: if(x==5) { var mydb= ........ ; } else { var mydb = ........ ; } but it didn't work because I can't declare a variable inside if statement. So I tried to do this: var mydb; if (x==5) { mydb= ............. ; } else { mydb=.............; } but id didn't work either because I had to initialize the variable (mydb). So the question is: I don't necessarily know the type of the variable, can I declare it anyway and then change the type inside the if statement?

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