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  • C++ explicit template specialization of templated constructor of templated class

    - by Victor Liu
    I have a class like template <class T> struct A{ template <class U> A(U u); }; I would like to write an explicit specialization of this for a declaration like A<int>::A(float); In the following test code, if I comment out the specialization, it compiles with g++. Otherwise, it says I have the wrong number of template parameters: #include <iostream> template <class T> struct A{ template <class U> A(T t, U *u){ *u += U(t); } }; template <> template <> A<int>::A<int,float>(int t, float *u){ *u += U(2*t); } int main(){ float f = 0; int i = 1; A<int>(i, &f); std::cout << f << std::endl; return 0; }

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  • Why is partial specialziation of a nested class template allowed, while complete isn't?

    - by drhirsch
    template<int x> struct A { template<int y> struct B {};. template<int y, int unused> struct C {}; }; template<int x> template<> struct A<x>::B<x> {}; // error: enclosing class templates are not explicitly specialized template<int x> template<int unused> struct A<x>::C<x, unused> {}; // ok So why is the explicit specialization of a inner, nested class (or function) not allowed, if the outer class isn't specialiced too? Strange enough, I can work around this behaviour if I only partially specialize the inner class with simply adding a dummy template parameter. Makes things uglier and more complex, but it works. Note: I need this feature for recursive templates of the inner class for a set of the outer class. To make things even more complicate, in reality I only need a template function instead of the inner class. But partial specialization of functions is generally disallowed somewhere else in the standard ^^

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  • Problems with Json Serialize Dictionary<Enum, Int32>

    - by dbemerlin
    Hi, whenever i try to serialize the dictionary i get the exception: System.ArgumentException: Type 'System.Collections.Generic.Dictionary`2[[Foo.DictionarySerializationTest+TestEnum, Foo, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' is not supported for serialization/deserialization of a dictionary, keys must be strings or object My Testcase is: public class DictionarySerializationTest { private enum TestEnum { A, B, C } public void SerializationTest() { Dictionary<TestEnum, Int32> data = new Dictionary<TestEnum, Int32>(); data.Add(TestEnum.A, 1); data.Add(TestEnum.B, 2); data.Add(TestEnum.C, 3); JavaScriptSerializer serializer = new JavaScriptSerializer(); String result = serializer.Serialize(data); // Throws } public void SerializationStringTest() { Dictionary<String, Int32> data = new Dictionary<String, Int32>(); data.Add(TestEnum.A.ToString(), 1); data.Add(TestEnum.B.ToString(), 2); data.Add(TestEnum.C.ToString(), 3); JavaScriptSerializer serializer = new JavaScriptSerializer(); String result = serializer.Serialize(data); // Succeeds } } Of course i could use .ToString() whenever i enter something into the Dictionary but since it's used quite often in performance relevant methods i would prefer using the enum. My only solution is using .ToString() and converting before entering the performance critical regions but that is clumsy and i would have to change my code structure just to be able to serialize the data. Does anyone have an idea how i could serialize the dictionary as <Enum, Int32>? I use the System.Web.Script.Serialization.JavaScriptSerializer for serialization.

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  • protobuf-net NOT faster than binary serialization?

    - by Ashish Gupta
    I wrote a program to serialize a 'Person' class using XMLSerializer, BinaryFormatter and ProtoBuf. I thought protobuf-net should be faster than the other two. Protobuf serialization was faster than XMLSerialization but much slower than the binary serialization. Is my understanding incorrect? Please make me understand this. Thank you for the help. Following is the output:- Person got created using protocol buffer in 347 milliseconds Person got created using XML in 1462 milliseconds Person got created using binary in 2 milliseconds Code below using System; using System.Collections.Generic; using System.Linq; using System.Text; using ProtoBuf; using System.IO; using System.Diagnostics; using System.Runtime.Serialization.Formatters.Binary; namespace ProtocolBuffers { class Program { static void Main(string[] args) { string XMLSerializedFileName = "PersonXMLSerialized.xml"; string ProtocolBufferFileName = "PersonProtocalBuffer.bin"; string BinarySerializedFileName = "PersonBinary.bin"; var person = new Person { Id = 12345, Name = "Fred", Address = new Address { Line1 = "Flat 1", Line2 = "The Meadows" } }; Stopwatch watch = Stopwatch.StartNew(); watch.Start(); using (var file = File.Create(ProtocolBufferFileName)) { Serializer.Serialize(file, person); } watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds.ToString()); Console.WriteLine("Person got created using protocol buffer in " + watch.ElapsedMilliseconds.ToString() + " milliseconds " ); watch.Reset(); watch.Start(); System.Xml.Serialization.XmlSerializer x = new System.Xml.Serialization.XmlSerializer(person.GetType()); using (TextWriter w = new StreamWriter(XMLSerializedFileName)) { x.Serialize(w, person); } watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds.ToString()); Console.WriteLine("Person got created using XML in " + watch.ElapsedMilliseconds.ToString() + " milliseconds"); watch.Reset(); watch.Start(); using (Stream stream = File.Open(BinarySerializedFileName, FileMode.Create)) { BinaryFormatter bformatter = new BinaryFormatter(); //Console.WriteLine("Writing Employee Information"); bformatter.Serialize(stream, person); } watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds.ToString()); Console.WriteLine("Person got created using binary in " + watch.ElapsedMilliseconds.ToString() + " milliseconds"); Console.ReadLine(); } } [ProtoContract] [Serializable] public class Person { [ProtoMember(1)] public int Id {get;set;} [ProtoMember(2)] public string Name { get; set; } [ProtoMember(3)] public Address Address {get;set;} } [ProtoContract] [Serializable] public class Address { [ProtoMember(1)] public string Line1 {get;set;} [ProtoMember(2)] public string Line2 {get;set;} } }

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  • Using OpenGL vertex buffers in C++.

    - by Ren
    I've loaded a Wavefront .obj file and drawn it in immediate mode, and it works fine. I'm now trying to draw the same model with a vertex buffer, but I have a question. My model data is organized in the following structures: struct Vert { double x; double y; double z; }; struct Norm { double x; double y; double z; }; struct Texcoord { double u; double v; double w; }; struct Face { unsigned int v[3]; unsigned int n[3]; unsigned int t[3]; }; struct Model { unsigned int vertNumber; unsigned int normNumber; unsigned int texcoordNumber; unsigned int faceNumber; Vert * vertArray; Norm * normArray; Texcoord * texcoordArray; Face * faceArray; }; As it is now, I don't think there is any redundant data, since multiple face structures can point to the same vertex, normal, or texture coordinate. When I make vbo's for the vertex positions, normals, and texture coordinates, and assign data to them with glBufferData, do I have to have make arrays with redundant data so that they will all have the same number of elements in the same order? I'd like to know if there is a simpler way to fill the buffers with the way I already have the model's data organized.

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  • How Pick a Column Value from a ListView Row - C#.NET

    - by peace
    How can i fetch the value 500 to a variable from the selected row? One solution would be to get the row position number and then the CustomerID position number. Can you please give a simple solution. SelectedItems means selected row and SubItems means the column values, so SelectedItem 0 and SubItem 0 would represent the value 500. Right? This is how i populate the listview: for (int i = 0; i < tempTable.Rows.Count; i++) { DataRow row = tempTable.Rows[i]; ListViewItem lvi = new ListViewItem(row["customerID"].ToString()); lvi.SubItems.Add(row["companyName"].ToString()); lvi.SubItems.Add(row["firstName"].ToString()); lvi.SubItems.Add(row["lastName"].ToString()); lstvRecordsCus.Items.Add(lvi); }

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  • How to efficiently compare the sign of two floating-point values while handling negative zeros

    - by François Beaune
    Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign. For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) { if (fabs(a) == 0.0f || fabs(b) == 0.0f) return true; return (a >= 0.0f) == (b >= 0.0f); } Assuming the IEEE floating-point model, here's a variant of SameSign that compiles to branchless code (at least with with Visual C++ 2008): bool SameSign(float a, float b) { int ia = binary_cast<int>(a); int ib = binary_cast<int>(b); int az = (ia & 0x7FFFFFFF) == 0; int bz = (ib & 0x7FFFFFFF) == 0; int ab = (ia ^ ib) >= 0; return (az | bz | ab) != 0; } with binary_cast defined as follow: template <typename Target, typename Source> inline Target binary_cast(Source s) { union { Source m_source; Target m_target; } u; u.m_source = s; return u.m_target; } I'm looking for two things: A faster, more efficient implementation of SameSign, using bit tricks, FPU tricks or even SSE intrinsics. An efficient extension of SameSign to three values.

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  • Emails sent using Flex app are delayed

    - by user363825
    I'm currently building an application in Flex that utilizes SMTP Mailer to automatically send out emails to the user when a particular condition is satisfied. The application checks this condition every 30 seconds. The condition is satisfied based on new records being returned from a database table. The problem is as follows: When the condition is first satisfied, the email is delivered to the user with no issues. The second time the condition is satisfied, the email is not delivered. In the smtp logs, the delivery attempt appears to get hung up on the following line: 354 Start mail input; end with <CRLF>.<CRLF> No error codes are present in the smtp logs, but I do trace the following event from the SMTP Mailer class: [Event type="mailError" bubbles=false cancelable=false eventPhase=2] When the condition is satisfied a third time, the email that was not delivered when the condition was satisfied the previous time is now delivered, along with the email for this instance. This pattern then repeats itself, with the next email not being sent followed by two emails being sent simulatneously when the condition is met again. The smtp server being used is Windows 2003, on an internal network. The email is being sent to an outlook account hosted on an exchange server that is also on this internal network. Here is the actionscript code that creates the SMTPMailer object: public var testMail:SMTPMailer = null; public function alertNotify() { Security.loadPolicyFile("crossdomain.xml"); this.testMail = new SMTPMailer("myserver.ec.local",25); this.testMail.addEventListener(SMTPEvent.MAIL_SENT, onEmailEvent); this.testMail.addEventListener(SMTPEvent.MAIL_ERROR, onEmailError); this.testMail.addEventListener(SMTPEvent.DISCONNECTED, onEmailConn); this.testMail.addEventListener(SecurityErrorEvent.SECURITY_ERROR, onEmailError); } Here is the code that creates the email body and calls the method to send the email: public function alertUser(emailAC:ArrayCollection):void { trace ("In alertUser() before send, testMail.connected = " + testMail.connected.toString()); var testStr:String = " Key Location Event Type Comment Update Time "; for each (var event:rEntity in emailAC) { testStr = testStr + "" + event.key.toString() + "" + event.xml.address.toString() + " " + [email protected]() + "" + [email protected]() + "" + [email protected]() + "" + event.xml.attribute("update-time").toXMLString() + ""; } testStr = testStr + ""; testMail.flush(); testMail.sendHTMLMail("[email protected]","[email protected]","Event Notification",testStr); } Really not sure where the email that gets hung up is being stored until it is finally sent.... Any suggestions as to how to begin to remedy this issue would be much appreciated.

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  • Object reference not set to an instance of an object

    - by MBTHQ
    Can anyone help with the following code? I'm trying to get data from the database colum to the datagridview... I'm getting error over here "Dim sql_1 As String = "SELECT * FROM item where item_id = '" + DataGridView_stockout.CurrentCell.Value.ToString() + "'"" Private Sub DataGridView_stockout_CellMouseClick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellMouseEventArgs) Handles DataGridView_stockout.CellMouseClick Dim i As Integer = Stock_checkDataSet1.Tables(0).Rows.Count > 0 Dim thiscur_stok As New System.Data.SqlClient.SqlConnection("Data Source=MBTHQ\SQLEXPRESS;Initial Catalog=stock_check;Integrated Security=True") ' Sql Query Dim sql_1 As String = "SELECT * FROM item where item_id = '" + DataGridView_stockout.CurrentCell.Value.ToString() + "'" ' Create Data Adapter Dim da_1 As New SqlDataAdapter(sql_1, thiscur_stok) ' Fill Dataset and Get Data Table da_1.Fill(Stock_checkDataSet1, "item") Dim dt_1 As DataTable = Stock_checkDataSet1.Tables("item") If i >= DataGridView_stockout.Rows.Count Then 'MessageBox.Show("Sorry, DataGridView_stockout doesn't any row at index " & i.ToString()) Exit Sub End If If 1 >= Stock_checkDataSet1.Tables.Count Then 'MessageBox.Show("Sorry, Stock_checkDataSet1 doesn't any table at index 1") Exit Sub End If If i >= Stock_checkDataSet1.Tables(1).Rows.Count Then 'MessageBox.Show("Sorry, Stock_checkDataSet1.Tables(1) doesn't any row at index " & i.ToString()) Exit Sub End If If Not Stock_checkDataSet1.Tables(1).Columns.Contains("os") Then 'MessageBox.Show("Sorry, Stock_checkDataSet1.Tables(1) doesn't any column named 'os'") Exit Sub End If 'DataGridView_stockout.Item("cs_stockout", i).Value = Stock_checkDataSet1.Tables(0).Rows(i).Item("os") Dim ab As String = Stock_checkDataSet1.Tables(0).Rows(i)(0).ToString() End Sub I keep on getting the error saying "Object reference not set to an instance of an object" I dont know where I'm going wrong. Help really appreciated!!

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  • dynamic lib can't find static lib

    - by renyufei
    env: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) app: Bin(main) calls dynamic lib(testb.so), and testb.so contains a static lib(libtesta.a). file list: main.c test.h a.c b.c then compile as: gcc -o testa.o -c a.c ar -r libtesta.a testa.o gcc -shared -fPIC -o testb.so b.c gcc -o main main.c -L. -ltesta -ldl then compile success, but runs an error: ./main: symbol lookup error: ./testb.so: undefined symbol: print code as follows: test.h #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <dlfcn.h> int printa(const char *msg); int printb(const char *msg); a.c #include "test.h" int printa(const char *msg) { printf("\tin printa\n"); printf("\t%s\n", msg); } b.c #include "test.h" int printb(const char *msg) { printf("in printb\n"); printa("called by printb\n"); printf("%s\n", msg); } main.c #include "test.h" int main(int argc, char **argv) { void *handle; int (*dfn)(const char *); printf("before dlopen\n"); handle = dlopen("./testb.so", RTLD_LOCAL | RTLD_LAZY); printf("after dlopen\n"); if (handle == NULL) { printf("dlopen fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dlsym\n"); dfn = dlsym(handle, "printb"); printf("after dlsym\n"); if (dfn == NULL) { printf("dlsym fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dfn\n"); dfn("printb func\n"); printf("after dfn\n"); exit(EXIT_SUCCESS); }

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  • Cannot write the output to a text file in cpp program

    - by swapedoc
    I have this input file "https://code.google.com/codejam/contest/351101/dashboard/do/A-large-practice.in?cmd=GetInputFile&problem=374101&input_id=1&filename=A-large-practice.in&redownload_last=1&agent=website&csrfmiddlewaretoken=OWMxNTVmMTUyODBiYjhhN2Q2OTM3ZGJiMTNhNDkwMDF8fDEzNzIxNzI1NTE3ODAzMjA%3D" I tried to read this file :-using freopen("filename.txt",r,stdin); and then I wanted the output written to be written to another text file which I can upload in this codejam practice question for the judge. #include<iostream> #include<cstdio> using namespace std; int main() { int t,k=0,a[2000]; freopen("ab.txt","r",stdin); scanf("%d",&t); while(t--) { freopen("cb.txt","w",stdout); int c; scanf("%d",&c); int n; scanf("%d",&n); for(int i=0;i<n;i++) scanf("%d",&a[i]); printf("Case #%d: ",++k); for(int i=0;i<n-1;i++) {for(int j=i+1;j<n;j++) if((a[i]+a[j])==c) {printf("%d %d\n",i+1,j+1); i=n;} } } return 0; } This is my code. Now the problem is the output file cb.txt contains only the last line of the input. I want the the whole of the output to be written to cb.txt,so what should I do.

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  • How memset initializes an array of integers by -1?

    - by haccks
    The manpage says about memset: #include <string.h> void *memset(void *s, int c, size_t n) The memset() function fills the first n bytes of the memory area pointed to by s with the constant byte c. It is clear that memset can't be used to initialize int array as shown below: int a[10]; memset(a, 1, sizeof(a)); it is because int is represented by 4 bytes (say) and one can not get the desired value for the integers in array a. But I often see the programmers use memset to set the int array elements to either 0 or -1. int a[10]; int b[10]; memset(a, 0, sizeof(a)); memset(b, -1, sizeof(b)); As per my understanding, initializing with integer 0 is OK because 0 can be represented in 1 byte (may be I am wrong in this context). But how it is possible to initialize b with -1 (a 4 bytes value)?

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  • Android: How to change my ExpandAnimation class to handle animation correctly?

    - by IamStalker
    here is my animation class that i have taken from Udnic - thanks m8, but i'm using it "not from closed position but from opened" and it's jumps and not behaving correctly. what should i do? public class ExpandAnimation extends Animation { private View mAnimatedView; private LinearLayout.LayoutParams mViewLayoutParams; public int mMarginStart, mMarginEnd; private boolean mIsVisibleAfter = false; private boolean mWasEndedAlready = false; private ImageView mImageView; /** * Initialize the animation * @param view The layout we want to animate * @param duration The duration of the animation, in ms */ public ExpandAnimation(View view, int duration, ImageView imageView) { setDuration(duration); mImageView = imageView; mAnimatedView = view; mViewLayoutParams = (LinearLayout.LayoutParams) view.getLayoutParams(); mMarginStart = mMarginEnd = 0; // decide to show or hide the view mIsVisibleAfter = (view.getVisibility() == View.VISIBLE); //mIsVisibleAfter = (mViewLayoutParams.bottomMargin == 0); mMarginStart = mViewLayoutParams.bottomMargin; if(mMarginStart != 0) mMarginStart = 0 - view.getHeight(); mMarginEnd = (mMarginStart == 0 ? (0 - view.getHeight()) : 0); view.setVisibility(View.VISIBLE); mImageView.setImageResource(R.drawable.expand_open); } @Override public void initialize(int width, int height, int parentWidth, int parentHeight) { super.initialize(width, height, parentWidth, parentHeight); } @Override protected void applyTransformation(float interpolatedTime, Transformation t) { super.applyTransformation(interpolatedTime, t); if (interpolatedTime < 1.0f) { // Calculating the new bottom margin, and setting it mViewLayoutParams.bottomMargin = mMarginStart + (int) ((mMarginEnd - mMarginStart) * interpolatedTime); // Invalidating the layout, making us seeing the changes we made mAnimatedView.requestLayout(); // Making sure we didn't run the ending before (it happens!) } else if (!mWasEndedAlready) { mViewLayoutParams.bottomMargin = mMarginEnd; mAnimatedView.requestLayout(); // if (mIsVisibleAfter) { if(mMarginEnd != 0) { mAnimatedView.setVisibility(View.GONE); mImageView.setImageResource(R.drawable.expand_close); } mWasEndedAlready = true; } } }

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  • Controls.remove() method not working in asp.net

    - by user279521
    I have a web app where the user can create dynamic textboxes at run time. When the user clicks SUBMIT, the form sends data to the database and I want remove the dynamic controls. The controls are created in the following code: Table tb = new Table(); tb.ID = "tbl"; for (i = 0; i < myCount; i += 1) { TableRow tr = new TableRow(); TextBox txtEmplName = new TextBox(); TextBox txtEmplEmail = new TextBox(); TextBox txtEmplPhone = new TextBox(); TextBox txtEmplPosition = new TextBox(); TextBox txtEmplOfficeID = new TextBox(); txtEmplName.ID = "txtEmplName" + i.ToString(); txtEmplEmail.ID = "txtEmplEmail" + i.ToString(); txtEmplPhone.ID = "txtEmplPhone" + i.ToString(); txtEmplPosition.ID = "txtEmplPosition" + i.ToString(); txtEmplOfficeID.ID = "txtEmplOfficeID" + i.ToString(); tr.Cells.Add(tc); tb.Rows.Add(tr); } Panel1.Controls.Add(tb); The Remove section of the code is: Table t = (Table)Page.FindControl("Panel1").FindControl("tbl"); foreach (TableRow tr in t.Rows) { for (i = 1; i < myCount; i += 1) { string txtEmplName = "txtEmplName" + i; tr.Controls.Remove(t.FindControl(txtEmplName)); string txtEmplEmail = "txtEmplEmail" + i; tr.Controls.Remove(t.FindControl(txtEmplEmail)); string txtEmplPhone = "txtEmplPhone" + i; tr.Controls.Remove(t.FindControl(txtEmplPhone)); string txtEmplPosition = "txtEmplPosition" + i; tr.Controls.Remove(t.FindControl(txtEmplPosition)); string txtEmplOfficeID = "txtEmplOfficeID" + i; tr.Controls.Remove(t.FindControl(txtEmplOfficeID)); } } However, the textboxes are still visible. Any ideas?

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  • Page Render Time in ASP.MVC in trace

    - by Pankaj
    Hello Everyone I want to check render time of each page in asp.net mvc application. i am using asp.net tracing. i have override the OnActionExecuting and OnActionExecuted methods on the BaseController class. protected override void OnActionExecuting(ActionExecutingContext filterContext) { string controler = filterContext.RouteData.Values["controller"].ToString(); string action = filterContext.RouteData.Values["action"].ToString(); StartTime =System.DateTime.Now; System.Diagnostics.Trace.Write(string.Format("Start '{0}/{1}' on: {2}", controler, action, System.DateTime.Now.UtilToISOFormat())); } protected override void OnActionExecuted(ActionExecutedContext filterContext) { string controler = filterContext.RouteData.Values["controller"].ToString(); string action = filterContext.RouteData.Values["action"].ToString(); var totalTime = System.DateTime.Now - this.StartTime; System.Diagnostics.Trace.Write(totalTime.ToString()); System.Diagnostics.Trace.Write(string.Format("End '{0}/{1}' on: {2}", controler, action, System.DateTime.Now.UtilToISOFormat())); } in OnActionExecuted method i get total time. how can i show this time in my http://localhost:51335/Trace.axd report?

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  • Converting Negative Decimal To String Loses the -

    - by coffeeaddict
    I'm required to send in a negative myDecimalValue.ToString("C"); The problem is if myDecimalValue is a negative, lets say -39, after conversion I'm getting $39.00 as the string not $39.00. So I'm not sure how to go about this. This is the utility method that takes in the decimal. If the decimal is negative, I want the ToString to show a negative public static BasicAmountType CreateBasicAmount(string amount, CurrencyCodeType currencyType) { BasicAmountType basicAmount = new BasicAmountType { currencyID = currencyType, Value = amount }; return basicAmount; } I could go either way, a C or F2, all I care is about getting that negative sign intothe string if the incoming decimal is negative. I suppose there's no way to do this unless I check for negativity inside my utility method here. I can't just send a negative number and expect the ToString to work and for the ToSTring to automatically see that the decimal is negative incoming?

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  • How to implement a simple queue properly?

    - by Stephen Hsu
    The current Go library doesn't provide the queue container. To implement a simple queue, I use circle array as the underlying data structure. It follows algorithms mentioned in TAOCP: Insert Y into queue X: X[R]<-Y; R<-(R+1)%M; if R=F then OVERFLOW. Delete Y from queue X: if F=R then UNDERFLOW; Y<-X[F]; F<-(F+1) % M. F: Front, R: Rear, M: Array length. Following is the code: package main import ( "fmt" ) type Queue struct { len int head, tail int q []int } func New(n int) *Queue { return &Queue{n, 0, 0, make([]int, n)} } func (p *Queue) Enqueue(x int) bool { p.q[p.tail] = x p.tail = (p.tail + 1) % p.len return p.head != p.tail } func (p *Queue) Dequeue() (int, bool) { if p.head == p.tail { return 0, false } x := p.q[p.head] p.head = (p.head + 1) % p.len return x, true } func main() { q := New(10) for i := 1; i < 13; i++ { fmt.Println(i, q.Enqueue(i)) } fmt.Println() for i := 1; i < 13; i++ { fmt.Println(q.Dequeue()) } } But the output is obviously wrong: 1 true 2 true 3 true 4 true 5 true 6 true 7 true 8 true 9 true 10 false 11 true 12 true 11 true 12 true 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false I think I need one more field to make the code work properly. What do you suggest?

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  • C++ brain teaser

    - by mxp
    I recently refactored code like this (MyClass to MyClassR). class SomeMember { long m_value; public: SomeMember() : m_value(0) {} SomeMember(int a) : m_value(a) {} SomeMember(int a, int b) : m_value(a+b) {} }; class MyClass { SomeMember m_first, m_second, m_third; public: MyClass(const bool isUp, const int x, const int y) { if (isUp) { m_first = SomeMember(x); m_second = SomeMember(y); m_third = SomeMember(x, y); } else { m_first = SomeMember(y); m_second = SomeMember(x); m_third = SomeMember(y, x); } } }; class MyClassR { SomeMember m_first, m_second, m_third; public: MyClassR(const bool isUp, const int x, const int y) : m_first(isUp ? x : y) , m_second(isUp ? y : x) , m_third(isUp ? x, y : y, x) { } }; What is the error, why does it compile (at least VC6 with warning level 3 doesn't complain) and what is the right way of doing it? I (assume) I already have all these answers but I think it's and interesting problem to share.

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  • Providing less than operator for one element of a pair

    - by Koszalek Opalek
    What would be the most elegant way too fix the following code: #include <vector> #include <map> #include <set> using namespace std; typedef map< int, int > row_t; typedef vector< row_t > board_t; typedef row_t::iterator area_t; bool operator< ( area_t const& a, area_t const& b ) { return( a->first < b->first ); }; int main( int argc, char* argv[] ) { int row_num; area_t it; set< pair< int, area_t > > queue; queue.insert( make_pair( row_num, it ) ); // does not compile }; One way to fix it is moving the definition of less< to namespace std (I know, you are not supposed to do it.) namespace std { bool operator< ( area_t const& a, area_t const& b ) { return( a->first < b->first ); }; }; Another obvious solution is defining less than< for pair< int, area_t but I'd like to avoid that and be able to define the operator only for the one element of the pair where it is not defined.

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  • Is it undefined behavior in the case of the private functions call in the initializer list?

    - by Alexey Malistov
    Consider the following code: struct Calc { Calc(const Arg1 & arg1, const Arg2 & arg2, /* */ const ArgN & argn) : arg1(arg1), arg2(arg2), /* */ argn(argn), coef1(get_coef1()), coef2(get_coef2()) { } int Calc1(); int Calc2(); int Calc3(); private: const Arg1 & arg1; const Arg2 & arg2; // ... const ArgN & argn; const int coef1; // I want to use const because const int coef2; // no modification is needed. int get_coef1() const { // calc coef1 using arg1, arg2, ..., argn; // undefined behavior? } int get_coef2() const { // calc coef2 using arg1, arg2, ..., argn and coef1; // undefined behavior? } }; struct Calc is not completely defined when I call get_coef1 and get_coef2 Is this code valid? Can I get UB?

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  • XAML get new width and height for Canvas

    - by Jack Navarro
    I have searched through many times but have not seen this before. Probably really simple question but can't wrap my head around it. Wrote a VSTO add-in for Excel that draws a Grid dynamically. Then launches a new window and replaces the contents of the Canvas with the generated Grid. The problem is with printing. When I call the print procedure the canvas.height and canvas.width returned is the old value prior to replacing it with the grid. Sample: string="<Grid Name=\"CanvasGrid\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">..Lots of stuff..</Grid>"; // Launch new window and replace the Canvas element WpfUserControl newWindow = new WpfUserControl(); newWindow.Show(); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 StringReader stringReader = new StringReader(LssAllcChrt); XmlReader xmlReader = XmlReader.Create(stringReader); Canvas myCanvas = newWindow.FindName("GrphCnvs") as Canvas; myCanvas.Children.Clear(); myCanvas.Children.Add((UIElement)XamlReader.Load(xmlReader)); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 but should be much larger the Grid spans all three of my screens Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens //Run code from WpfUserControl.cs after it loads from button click Grid testGrid = canvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens So basically I have no way of telling what my new width and height are.

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  • Euler Project Help (Problem 12) - Prime Factors and the like

    - by Richie_W
    I hate to have to ask, but I'm pretty stuck here. I need to test a sequence of numbers to find the first which has over 500 factors: http://projecteuler.net/index.php?section=problems&id=12 -At first I attempted to brute force the answer (finding a number with 480 after a LONG time) -I am now looking at determining the prime factors of a number and then use them to find all other factors. I am currently at the stage where I can get an array of prime factors for any number I input - i.e 300 has the prime factors 2 2 3 5 5 Using this array of prime factors I need to be able to calculate the remaining factors - This is the part I am stuck on. Basically, as I understand it, I need to calculate ALL possible combinations of the numbers in the array... i.e 2 * 2 2 * 2 * 3 2 * 2 * 3 * 5 2 * 3 2 * 3 * 3 ...and so forth - But where it gets interesting is with things like... 2 * 5 2 * 3 * 5 ...i.e Numbers which are not adjacent to each other in the array I can't think of a way to code this in a generic fashion for any length array... I need help! P.S - I am working in Java EDIT: My brute force code - As it has been suggested brute forcing the problem will work and so there may be an error in my code :( package euler.problem12; public class Solution { public static void main(String[] args) { int next = 1; int triangle = 0; int maxFactors = 0; while(true) { triangle = triangle + next; int factors = 1; int max = (int) triangle / 2; for(int i = 1; i <= max; ++i) { if(triangle % i == 0) { factors ++; } } if(factors > maxFactors) { maxFactors = factors; System.out.println(triangle + "\t" + factors); } next++; } } }

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  • Association Mapping Details confusion?

    - by AaronLS
    I have never understood why the associations in EntityFramework look the way they do in the Mapping Details window. When I select the line between 2 tables for an association, for example FK_ApplicationSectionsNodes_FormItems, it shows this: Association Maps to ApplicationSectionNodes FormItems (key symbol) FormItemId:Int32 <--> FormItemId:int ApplicationSectionNodes (key symbol) NodeId:Int32 <--> (key symbol) NodeId : int Fortunately this one was create automatically for me based on the foreign key constraints in my database, but whenever no constraints exist, I have a hard to creating associations manually(when the database doesn't have a diagram setup) because I don't understand the mapping details for associations. FormItems table has a primary key identity column FormItemId, and ApplicationSectionNodes contains a FormItemId column that is the foreign key and has NodeId as a primary key identity column. What really makes no sense to me is why the association has anything listed about the NodeId, when NodeId doesn't have anything to do with the foreign key relationship? (It's even more confusing with self referencing relationships, but maybe if I could understand the above case I'd have a better handle). CREATE TABLE [dbo].[ApplicationSectionNodes]( [NodeID] [int] IDENTITY(1,1) NOT NULL, [OutlineText] [varchar](5000) NULL, [ParentNodeID] [int] NULL, [FormItemId] [int] NULL, CONSTRAINT [PK_ApplicationSectionNodes] PRIMARY KEY CLUSTERED ( [NodeID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY], CONSTRAINT [UQ_ApplicationSectionNodesFormItemId] UNIQUE NONCLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] FOREIGN KEY([ParentNodeID]) REFERENCES [dbo].[ApplicationSectionNodes] ([NodeID]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_FormItems] FOREIGN KEY([FormItemId]) REFERENCES [dbo].[FormItems] ([FormItemId]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_FormItems] GO FormItems Table: CREATE TABLE [dbo].[FormItems]( [FormItemId] [int] IDENTITY(1,1) NOT NULL, [FormItemType] [int] NULL, CONSTRAINT [PK_FormItems] PRIMARY KEY CLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[FormItems] WITH NOCHECK ADD CONSTRAINT [FK_FormItems_FormItemTypes] FOREIGN KEY([FormItemType]) REFERENCES [dbo].[FormItemTypes] ([FormItemTypeId]) GO ALTER TABLE [dbo].[FormItems] NOCHECK CONSTRAINT [FK_FormItems_FormItemTypes] GO

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  • Assign C++ instance method to a global-function-pointer ?

    - by umanga
    Greetings, My project structure is as follows: \- base (C static library) callbacks.h callbacks.c paint_node.c . . * libBase.a \-app (C++ application) main.cpp In C library 'base' , I have declared global-function-pointer as: in singleheader file callbacks.h #ifndef CALLBACKS_H_ #define CALLBACKS_H_ extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); #endif /* CALLBACKS_H_ */ in single C file they are initialized as callbacks.c #include "callbacks.h" void (*putPixelCallBack)(); void (*putImageCallBack)(); Other C files access this callback-functions as: paint_node.c #include "callbacks.h" void paint_node(node *node,int index){ //Call callbackfunction . . putPixelCallBack(node->x,node->y,index); } I compile these C files and generate a static library 'libBase.a' Then in C++ application, I want to assign C++ instance method to this global function-pointer: I did something like follows : in Sacm.cpp file #include "Sacm.h" extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); void Sacm::doDetection() { putPixelCallBack=(void(*)())&paintPixel; //call somefunctions in 'libBase' C library } void Sacm::paintPixel(int x,int y,int index) { qpainter.begin(this); qpainter.drawPoint(x,y); qpainter.end(); } But when compiling it gives the error: sacmtest.cpp: In member function ‘void Sacm::doDetection()’: sacmtest.cpp:113: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say ‘&Sacm::paintPixel’ sacmtest.cpp:113: error: converting from ‘void (Sacm::)(int, int, int)’ to ‘void ()()’ Any tips?

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  • Java Concurrency in practice sample question

    - by andy boot
    I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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