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  • Using reshape + cast to aggregate over multiple columns

    - by DamonJW
    In R, I have a data frame with columns for Seat (factor), Party (factor) and Votes (numeric). I want to create a summary data frame with columns for Seat, Winning party, and Vote share. For example, from the data frame df <- data.frame(party=rep(c('Lab','C','LD'),times=4), votes=c(1,12,2,11,3,10,4,9,5,8,6,15), seat=rep(c('A','B','C','D'),each=3)) I want to get the output seat winner voteshare 1 A C 0.8000000 2 B Lab 0.4583333 3 C C 0.5000000 4 D LD 0.5172414 I can figure out how to achieve this. But I'm sure there must be a better way, probably a cunning one-liner using Hadley Wickham's reshape package. Any suggestions? For what it's worth, my solution uses a function from my package djwutils_2.10.zip and is invoked as follows. But there are all sorts of special cases it doesn't deal with, so I'd rather rely on someone else's code. aggregateList(df, by=list(seat=seat), FUN=list(winner=function(x) x$party[which.max(x$votes)], voteshare=function(x) max(x$votes)/sum(x$votes)))

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  • Overriding Ruby's spaceship operator <=>

    - by ericsteen1
    I am trying to override Ruby's <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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  • Can I Cast a Generic List by Type??

    - by CrazyJoe
    NavigatorItem NavItem = (NavigatorItem)cboItems.SelectedItem; lblTitle.Text = NavItem.Title; RadWrapPanel Panel = new RadWrapPanel(); Type t = NavItem.ItemsType; //<------ The Type inside my List is here. List<???> items = (List<???>)NavItem.Items; // <----Here Is the problem foreach (object item in items) { Panel.Children.Add((UIElement)Activator.CreateInstance(NavItem.Display,item)); } ItemsContainer.Content = Panel; In code above i need to get the type of items on t variable to put into of my generic List. Help Please!!!

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  • C++ vector<T>::iterator operator +

    - by Tom
    Hi, Im holding an iterator that points to an element of a vector, and I would like to compare it to the next element of the vector. Here is what I have Class Point{ public: float x,y; } //Somewhere in my code I do this vector<Point> points = line.getPoints(); foo (points.begin(),points.end()); where foo is: void foo (Vector<Point>::iterator begin,Vector<Point>::iterator end) { std::Vector<Point>::iterator current = begin; for(;current!=end-1;++current) { std::Vector<Point>::iterator next = current + 1; //Compare between current and next. } } I thought that this would work, but current + 1 is not giving me the next element of the vector. I though operator+ was the way to go, but doesnt seem so. Is there a workaround on this? THanks

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  • Is It Safe to Cast Away volatile?

    - by Yan Cheng CHEOK
    Most of the time, I am doing this way. class a { public: ~ a() { i = 100; // OK delete (int *)j; // Compiler happy. But, is it safe? // Error : delete j; } private: volatile int i; volatile int *j; }; int main() { a aa; } However, I saw an article here: https://www.securecoding.cert.org/confluence/display/seccode/EXP32-C.+Do+not+access+a+volatile+object+through+a+non-volatile+reference Casting away volatile allows access to an object through a non-volatile reference. This can result in undefined and perhaps unintended program behavior. So, what will be the workaround for my above code example?

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  • "assignment makes integer from pointer without a cast " warning in c

    - by mekasperasky
    #include<stdio.h> /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i=0,j; char a,b[20],c[30]; FILE *fp1,*fp2; c[0]='"if"; c[1]="then"; c[2]="else"; c[3]="switch"; c[4]="printf"; c[5]="scanf"; c[6]="NULL"; c[7]="int"; c[8]="char"; c[9]="float"; c[10]="long"; c[11]="double"; c[12]="char"; c[13]="const"; c[14]="continue"; c[15]="break"; c[16]="for"; c[17]="size of"; c[18]="register"; c[19]="short"; c[20]="auto"; c[21]="while"; c[22]="do"; c[23]="case"; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer fp2=fopen("lext.txt","w"); //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; while(!feof(fp1)) { a=fgetc(fp1); if(a!=' ') { b[i]=a; } else { for (j=0;j<23;j++) { if(c[j]==b) { fprintf(fp2, "%.20s\n", c[j]); continue ; } b[i]='\0'; fprintf(fp2, "%.20s\n", b); i=0; continue; } //else if //{ i=i+1; /*Switch(a) { case EOF :return eof; case '+':sym=sym+1; case '-':sym=sym+1; case '*':sym=sym+1; case '/':sym=sym+1; case '%':sym=sym+1; case ' */ } fclose(fp1); fclose(fp2); return 0; } This is my c code for lexical analysis .. its giving warnings and also not writing anything into the lext file ..

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  • C# == operator in Immediate window behaves differently than at run-time

    - by Damiano
    Try the following in the Immediate window: object a1 = "a"; object a2 = "a"; a1==a2 // outputs false and you'll see that a1 == a2 outputs false. However, at runtime in either a window app or console, you'll get true: object t1 = "a"; object t2 = "a"; MessageBox.Show((t1 == t2).ToString()); // outputs true The runtime behavior is consistent with the definition for the == operator and strings. Does anybody know if this a bug in the Immediate window?

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  • Suppress error with @ operator in PHP

    - by Mez
    In your opinion, is it ever valid to use the @ operator to suppress an error/warning in PHP whereas you may be handling the error? If so, in what circumstances would you use this? Code examples are welcome. Edit: Note to repliers. I'm not looking to turn error reporting off, but, for example, common practice is to use @fopen($file); and then check afterwards... but you can get rid of the @ by doing if (file_exists($file)) { fopen($file); } else { die('File not found'); } or similar. I guess the question is - is there anywhere that @ HAS to be used to supress an error, that CANNOT be handled in any other manner?

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  • Logical xor operator in c++?

    - by RAC
    Is there such a thing? First time I encountered a practical need for it, but I don't see one listed in stroustrup. I intend to write: // Detect when exactly one of A,B is equal to five. return (A==5) ^^ (B==5); But there is no ^^ operator. Can I use bitwise ^ here and get the right answer (regardless of machine representation of true and false)? I never mix & and &&, or | and ||, so I hesitate to do that with ^ and ^^. I'd be more comfortable writing my own "bool XOR(bool,bool)" function instead.

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  • Casting to specific asp.net page type

    - by DEH
    I have an asp.net page with a code-behind class definition as follows: public partial class examplepage : System.Web.UI.Page I'd like to set a public property within the page that I can reference from other classes. My understanding is that if I cast to examplepage then I should be able to get at the public property that is specific to example page, as in: string test=((examplepage)HttpContext.Current.Handler).propertyX; However, when I try casting as above the compiler does not recognise examplepage. Can anyone tell me how I can cast? I have no specific namespaces defined. Thanks

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  • Invalid Cast Exception with Update Panel

    - by user1593175
    On Button Click Protected Sub btnSubmit_Click(sender As Object, e As System.EventArgs) Handles btnSubmit.Click MsgBox("INSIDE") If SocialAuthUser.IsLoggedIn Then Dim accountId As Integer = BLL.getAccIDFromSocialAuthSession Dim AlbumID As Integer = BLL.createAndReturnNewAlbumId(txtStoryTitle.Text.Trim, "") Dim URL As String = BLL.getAlbumPicUrl(txtStoryTitle.Text.Trim) Dim dt As New DataTable dt.Columns.Add("PictureID") dt.Columns.Add("AccountID") dt.Columns.Add("AlbumID") dt.Columns.Add("URL") dt.Columns.Add("Thumbnail") dt.Columns.Add("Description") dt.Columns.Add("AlbumCover") dt.Columns.Add("Tags") dt.Columns.Add("Votes") dt.Columns.Add("Abused") dt.Columns.Add("isActive") Dim Row As DataRow Dim uniqueFileName As String = "" If Session("ID") Is Nothing Then lblMessage.Text = "You don't seem to have uploaded any pictures." Exit Sub Else **Dim FileCount As Integer = Request.Form(Request.Form.Count - 2)** Dim FileName, TargetName As String Try Dim Path As String = Server.MapPath(BLL.getAlbumPicUrl(txtStoryTitle.Text.Trim)) If Not IO.Directory.Exists(Path) Then IO.Directory.CreateDirectory(Path) End If Dim StartIndex As Integer Dim PicCount As Integer For i As Integer = 0 To Request.Form.Count - 1 If Request.Form(i).ToLower.Contains("jpg") Or Request.Form(i).ToLower.Contains("gif") Or Request.Form(i).ToLower.Contains("png") Then StartIndex = i + 1 Exit For End If Next For i As Integer = StartIndex To Request.Form.Count - 4 Step 3 FileName = Request.Form(i) '## If part here is not kaam ka..but still using it for worst case scenario If IO.File.Exists(Path & FileName) Then TargetName = Path & FileName 'MsgBox(TargetName & "--- 1") Dim j As Integer = 1 While IO.File.Exists(TargetName) TargetName = Path & IO.Path.GetFileNameWithoutExtension(FileName) & "(" & j & ")" & IO.Path.GetExtension(FileName) j += 1 End While Else uniqueFileName = Guid.NewGuid.ToString & "__" & FileName TargetName = Path & uniqueFileName End If IO.File.Move(Server.MapPath("~/TempUploads/" & Session("ID") & "/" & FileName), TargetName) PicCount += 1 Row = dt.NewRow() Row(1) = accountId Row(2) = AlbumID Row(3) = URL & uniqueFileName Row(4) = "" Row(5) = "No Desc" Row(6) = "False" Row(7) = "" Row(8) = "0" Row(9) = "0" Row(10) = "True" dt.Rows.Add(Row) Next If BLL.insertImagesIntoAlbum(dt) Then lblMessage.Text = PicCount & IIf(PicCount = 1, " Picture", " Pictures") & " Saved!" lblMessage.ForeColor = Drawing.Color.Black Dim db As SqlDatabase = Connection.connection Using cmd As DbCommand = db.GetSqlStringCommand("SELECT PictureID,URL FROM AlbumPictures WHERE AlbumID=@AlbumID AND AccountID=@AccountID") db.AddInParameter(cmd, "AlbumID", Data.DbType.Int32, AlbumID) db.AddInParameter(cmd, "AccountID", Data.DbType.Int32, accountId) Using ds As DataSet = db.ExecuteDataSet(cmd) If ds.Tables(0).Rows.Count > 0 Then ListView1.DataSource = ds.Tables(0) ListView1.DataBind() Else lblMessage.Text = "No Such Album Exists." End If End Using End Using 'WebNavigator.GoToResponseRedirect(WebNavigator.URLFor.ReturnUrl("~/Memories/SortImages.aspx?id=" & AlbumID)) Else 'TODO:we'll show some error msg End If Catch ex As Exception MsgBox(ex.Message) lblMessage.Text = "Oo Poop!!" End Try End If Else WebNavigator.GoToResponseRedirect(WebNavigator.URLFor.LoginWithReturnUrl("~/Memories/CreateAlbum.aspx")) Exit Sub End If End Sub The above code works fine.I have added an Update Panel in the page to avoid post back, But when i add the button click as a trigger <Triggers> <asp:AsyncPostBackTrigger ControlID="btnSubmit" /> </Triggers> in the update panel to avoid post back, i get the following error.This happens when i add the button click as a Trigger to the update panel.

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  • How to replace a codebehind method with an aspx method using ternary operator

    - by user466663
    I have an asp:hyperlink control as part of a gridview template. The code in the aspx page is given below: asp:HyperLink runat="server" ID="lnkEdit" ToolTip="Edit article" NavigateUrl='<%# GetUrl(Eval("ID").ToString(), Eval("CategoryID").ToString()) %' ImageUrl="~/Images/Edit.gif" The NavigateUrl value is obtained from the codebehind method GetUrl(string, string). The code works fine and is as follows: protected string GetUrl(string id, string categoryID) { var CategoryID = string.Empty; if (!String.IsNullOrEmpty(Request.QueryString["CatID"])) { CategoryID = Request.QueryString["CatID"].ToString(); } else if (!String.IsNullOrEmpty(categoryID)) { CategoryID = categoryID; } return "~/TBSArticles/WriteOrEditArticle.aspx?ID=" + id + "&CatID=" + CategoryID; } I want to replace the code behind method by using a ternary operator within the aspx page. I tried something like below, but didn't work: asp:HyperLink runat="server" ID="lnkEdit" ToolTip="Edit article" NavigateUrl='<%# "~/TBSArticles/WriteOrEditArticle.aspx?ID=" + Eval("ID") + "&CatID=" + Eval(this.Request.QueryString["CatID"].ToString()) != ""? this.Request.QueryString["CatID"] : Eval("CategoryID")) %' ImageUrl="~/Images/Edit.gif" Any help will be greatly appreciated. Thanks

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  • C++: Why does gcc prefer non-const over const when accessing operator[]?

    - by JonasW
    This question might be more appropriately asked regarding C++ in general, but as I am using gcc on linux that's the context. Consider the following program: #include <iostream> #include <map> #include <string> using namespace std; template <typename TKey, typename TValue> class Dictionary{ public: map<TKey, TValue> internal; TValue & operator[](TKey const & key) { cout << "operator[] with key " << key << " called " << endl; return internal[key]; } TValue const & operator[](TKey const & key) const { cout << "operator[] const with key " << key << " called " << endl; return internal.at(key); } }; int main(int argc, char* argv[]) { Dictionary<string, string> dict; dict["1"] = "one"; cout << "first one: " << dict["1"] << endl; return 0; } When executing the program, the output is: operator[] with key 1 called operator[] with key 1 called first one: one What I would like is to have the compiler choose the operator[]const method instead in the second call. The reason is that without having used dict["1"] before, the call to operator[] causes the internal map to create the data that does not exist, even if the only thing I wanted was to do some debugging output, which of course is a fatal application error. The behaviour I am looking for would be something like the C# index operator which has a get and a set operation and where you could throw an exception if the getter tries to access something that doesn't exist: class MyDictionary<TKey, TVal> { private Dictionary<TKey, TVal> dict = new Dictionary<TKey, TVal>(); public TVal this[TKey idx] { get { if(!dict.ContainsKey(idx)) throw KeyNotFoundException("..."); return dict[idx]; } set { dict[idx] = value; } } } Thus, I wonder why the gcc prefers the non-const call over the const call when non-const access is not required.

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  • Why operator= returns reference not const reference

    - by outmind
    The original question is related to overloading operator= and I like to share my findings as it was nontrivial for me to find them. I cannot imagine reasonable example to use (a=b) as lvalue. With the help of IRC and google I've found the next article: http://msdn.microsoft.com/en-us/magazine/cc301415.aspx it provides two examples. (a=b)=c f(T& ); f(a=b) but both a bit not good, as first violate associativity and I believe that it is bad practice. The second one give me the same feeling. Could you provide more good examples why it should be non constant?

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  • Cast vector<T> to vector<const T>

    - by user345386
    I have a member variable of type vector (where is T is a custom class, but it could be int as well.) I have a function from which I want to return a pointer to this vector, but I don't want the caller to be able to change the vector or it's items. So I want the return type to be const vector* None of the casting methods I tried worked. The compiler keeps complaining that T is not compatible with const T. Here's some code that demonstrates the gist of what I'm trying to do; vector<int> a; const vector<const int>* b = (const vector<const int>* ) (&a); This code doesn't compile for me. Thanks in advance!

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  • How does the increment operator (++) work on DateTime in C#

    - by sohtimsso1970
    What happens if you use the increment operator (++) on a DateTime type in C#? For instance, if I did this: DateTime blah = new DateTime(2010, 12, 24); blah++; What does blah become? Does that increment by a tick or a day? Or is that even legal? I don't have a dev environment around, and won't for a few days, or I would just try it and find out. I was too curious to wait so I figured I'd ask the community.

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  • implict type cast in generic method

    - by bitbonk
    why do I get a compiler error in the following code stating: Cannot implicty convert type SpecialNode to T even though T must derive from NodeBase as I defined in the where clause and even though SpecialNode actually derived from NodeBase? public static T GetNode<T>() where T : NodeBase { if (typeof(T) == typeof(SpecialNode)) { return ThisStaticClass.MySpecialNode; // <-- compiler error } if (typeof(T) == typeof(OtherSpecialNode)) { return ThisStaticClass.MyOtherSpecialNode; // <-- compiler error } ... return default(T); }

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  • Call Generic method using runtime type and cast return object

    - by markpirvine
    I'm using reflection to call a generic method with a type determined at runtime. My code is as follows: Type tType = Type.GetType(pLoadOut.Type); MethodInfo method = typeof(ApiSerialiseHelper).GetMethod("Deserialise", new Type[] { typeof(string) }); MethodInfo generic = method.MakeGenericMethod(tType); generic.Invoke(obj, new object[] { pLoadOut.Data }); This works ok. However the generic.Invoke method returns an object, but what I would like is the type determined at runtime. Is this possible with this approach, or is there a better option? Mark

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  • Interface member name conflicts in ActionScript 3

    - by Aaron
    I am trying to create an ActionScript 3 class that implements two interfaces. The interfaces contain member functions with different signatures but the same name: public interface IFoo { function doStuff(input:int):void; } public interface IBar { function doStuff(input1:String, input2:Number):void; } public class FooBar implements IFoo, IBar { // ??? } In C# this problem can be solved with explicit interface implementations, but as far as I can tell ActionScript does not have that feature. Is there any way to create a class that implements both interfaces?

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