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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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  • 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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  • 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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  • 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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  • 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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  • 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 Type of a VARIANT

    - by nimo
    Hi, I'm having a VARIANT with its type set to VT_R8. Subsequently I need to change its type to VT_BSTR. I would like know whether there is a way of resetting a VARIANT status. Thus, I noticed that every time I set value to the VARIANT (in my case, its double) , VARIANT itself set its bstrVal member to a bad pointer, even though I set bstrVal member to NULL at the initialization of VARIANT. Why such thing is happening ? Is it safe to use a VARIANT as structure where both dbVal and bstrVal member are set ? Please clarify, thank you.

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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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  • 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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  • Core Data: Detecting the type and casting it

    - by Tim Sullivan
    I have set up a Core Data model that includes an entity, Item with a 1-M relationship with the abstract entity Place, so that an item has many places. There are several entities with the parent set to Place. I want to set up several UI elements depending on the descendent place types. I have a loop that looks something like this: for (Place *place in item.places) { } ... but I'm not sure how to detect what type the place is, and how to cast it to the proper type so that I can access its properties. Thanks for any help!

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  • anonymous type and multiple properties

    - by ognjenb
    I have this error: An anonymous type cannot have multiple properties with the same name. Whether this can be resolved with alias ie, whether an alias exists in LINQ var device_query = from d in DevicesEntities.device join dt in DevicesEntities.devicetype on d.DeviceTypeId equals dt.Id join l in DevicesEntities.location on d.Id equals l.DeviceId join loc in DevicesEntities.locationname on l.LocationNameId equals loc.Id where l.DeviceId == d.Id select new { d.Id, d.DeviceTypeId, d.SerialNumber, d.FirmwareRev, d.ProductionDate, d.ReparationDate, d.DateOfLastCalibration, d.DateOfLastCalibrationCheck, d.CalCertificateFile, d.Notes, d.TestReportFile, d.WarrantyFile, d.CertificateOfOriginFile, d.QCPermissionFile, d.Reserved, d.ReservedFor, d.Weight, d.Price, d.SoftwareVersion, dt.Name, dt.ArticleNumber, dt.Type, l.StartDate, //AS LastStartDate, l.LocationNameId, loc.Name //in this line I have problem };

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  • Casting in mixed type calculations in C?

    - by yCalleecharan
    Hi, If I define these variables: double x0, xn, h; int n; and I have this mathematical expression: h = (xn - x0)/n; Is it necessary that I cast n into double prior doing the division for maximum accuracy like in h = (xn - x0)/ (double) n; I wrote a program to check the above but both expressions give the same answers. I understand that C will promote the integer to double type as variables xn and x0 are of type double but strangely enough in a book, the second expression with casting was emphasized. Thanks a lot...

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  • return type while using GMP.h header file

    - by Raveesh_Kumar
    While i m using gmp.h header file. i need a fuction which takes inputs of type mpz_t and return mpz_t type too. I m very beginner of using gmp.h So, Here is snaps follows of my approached code.... mpz_t sum_upto(mpz_t max) { mpz_t sum; mpz_init(sum); mpz_init(result); for(int i=0;i<=max-1;i++) mpz_add_ui(sum,sum,pow(2,i)); return sum; } but it will show error 1 ." pow has been not used in this scope.",although i have added math.h in very beginnig of the file. 2 . sum_upto declared as function returning an array... do tell as soon as possible. i have to complete my very big project....

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  • How to convert from one co-ordinate system to another (graphics)

    - by Dororo
    I've been having issues with this for a little while now. I feel like I should know this but I can't for the life of me remember. How can I map the screen pixels to their respective 'graphical' x,y positions? The co-ordinate systems have been configured to start at the bottom left (0,0) and increase to the top-right. I want to be able to zoom, so I know that I need to configure the zoom distance into the answer. Screen |\ Some Quad | \--------|\Qx | \ Z | \ | \ \|Qy \ | Sx\ |Sy \| I want to know which pixels on my screen will have the quad on it. Obviously as Z decreases, the quad will occupy more of the screen, and as Z increases it will occupy less, but how exactly are these calculated? Thanks for any help.

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