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• The code works but when using printf it gives me a weird answer. Help please [closed]

  - by user71458

  //Programmer-William Chen //Seventh Period Computer Science II //Problem Statement - First get the elapsed times and the program will find the //split times for the user to see. // //Algorithm- First the programmer makes the prototype and calls them in the //main function. The programmer then asks the user to input lap time data. //Secondly, you convert the splits into seconds and subtract them so you can //find the splits. Then the average is all the lap time's in seconds. Finally, //the programmer printf all the results for the user to see. #include <iostream> #include <stdlib.h> #include <math.h> #include <conio.h> #include <stdio.h> using namespace std; void thisgetsElapsedTimes( int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5); //this is prototype void thisconvertstoseconds ( int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5, int &split1, int &split2, int &split3, int &split4, int &split5);//this too void thisfindsSplits(int &m1, int &m2, int &m3, int &m4, int &m5, int &split1, int &split2, int &split3, int &split4, int &split5, int &split6, int &split7, int &split8, int &split9, int &split10);// this is part of prototype void thisisthesecondconversation (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S,int &split2S, int &split3S, int &split4S, int &split5S, int &split1, int &split2, int &split3, int &split4, int &split5);//this gets a value void thisfindstheaverage(double &average, int &split1, int &split2, int &split3, int &split4, int &split5);//and this void thisprintsstuff( int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S, int &split2S, int &split3S, int &split4S, int &split5S, double &average); //this prints int main(int argc, char *argv[]) { int m1, m2, m3, m4, m5, s1, s2, s3, s4, s5, split1, split2, split3, split4, split5, split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S; int split6, split7, split8, split9, split10; double average; char thistakescolon; thisgetsElapsedTimes ( m1, m2, m3, m4, m5, s1, s2, s3, s4, s5); thisconvertstoseconds ( m1, m2, m3, m4, m5, s1, s2, s3, s4, s5, split1, split2, split3, split4, split5); thisfindsSplits ( m1, m2, m3, m4, m5, split1, split2, split3, split4, split5, split6, split7, split8, split9, split10); thisisthesecondconversation ( split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S, split1, split2, split3, split4, split5); thisfindstheaverage ( average, split1, split2, split3, split4, split5); thisprintsstuff ( split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S, average); // these are calling statements and they call from the main function to the other functions. system("PAUSE"); return 0; } void thisgetsElapsedTimes(int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5) { char thistakescolon; cout << "Enter the elapsed time:" << endl; cout << " Kilometer 1 "; cin m1 thistakescolon s1; cout << " Kilometer 2 "; cin m2 thistakescolon s2; cout << " Kilometer 3 " ; cin m3 thistakescolon s3; cout << " Kilometer 4 "; cin m4 thistakescolon s4; cout << " Kilometer 5 "; cin m5 thistakescolon s5; // this gets the data required to get the results needed for the user to see // . } void thisconvertstoseconds (int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5, int &split1, int &split2, int &split3, int &split4, int &split5) { split1 = (m1 * 60) + s1;//this converts for minutes to seconds for m1 split2 = (m2 * 60) + s2;//this converts for minutes to seconds for m2 split3 = (m3 * 60) + s3;//this converts for minutes to seconds for m3 split4 = (m4 * 60) + s4;//this converts for minutes to seconds for m4 split5 = (m5 * 60) + s5;//this converts for minutes to seconds for m5 } void thisfindsSplits (int &m1, int &m2, int &m3, int &m4, int &m5,int &split1, int &split2, int &split3, int &split4, int &split5, int &split6, int &split7, int &split8, int &split9, int &split10)//this is function heading { split6 = split1; //this is split for the first lap. split7 = split2 - split1;//this is split for the second lap. split8 = split3 - split2;//this is split for the third lap. split9 = split4 - split3;//this is split for the fourth lap. split10 = split5 - split4;//this is split for the fifth lap. } void thisfindstheaverage(double &average, int &split1, int &split2, int &split3, int &split4, int &split5) { average = (split1 + split2 + split3 + split4 + split5)/5; // this finds the average from all the splits in seconds } void thisisthesecondconversation (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S,int &split2S, int &split3S, int &split4S, int &split5S, int &split1, int &split2, int &split3, int &split4, int &split5) { split1M = split1 * 60; //this finds the split times split1S = split1M - split1 * 60; //then this finds split2M = split2 * 60; //and all of this split2S = split2M - split2 * 60; //does basically split3M = split3 * 60; //the same thing split3S = split3M - split3 * 60; //all of it split4M = split4 * 60; //it's also a split4S = split4M - split4 * 60; //function split5M = split5 * 60; //and it finds the splits split5S = split5M - split5 * 60; //for each lap. } void thisprintsstuff (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S, int &split2S, int &split3S, int &split4S, int &split5S, double &average)// this is function heading { printf("\n kilometer 1 %d" , ":02%d",'split1M','split1S'); printf("\n kilometer 2 %d" , ":02%d",'split2M','split2S'); printf("\n kilometer 3 %d" , ":02%d",'split3M','split3S'); printf("\n kilometer 4 %d" , ":02%d",'split4M','split4S'); printf("\n kilometer 5 %d" , ":02%d",'split5M','split5S'); printf("\n your average pace is ",'average',"per kilometer \n", "William Chen\n"); // this printf so the programmer // can allow the user to see // the results from the data gathered. }

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• Override ToString() in your Classes

  - by psheriff

  One of the reasons I love teaching is because of the questions that I get from attendees. I was giving a presentation at DevConnections and was showing a collection of Product objects. When I hovered over the variable that contained the collection, it looked like Figure 2. As you can see in the collection, I have actual product names of my videos from www.pdsa.com/videos being displayed. To get your data to appear in the data tips you must override the ToString() method in your class. To illustrate this, take the following simple Product class shown below: public class Product{  public string ProductName { get; set; }  public int ProductId { get; set; }} This class does not have an override of the ToString() method so if you create a collection of Product objects you will end up with data tips that look like Figure 1. Below is the code I used to create a collection of Product objects. I have shortened the code in this blog, but you can get the full source code for this sample by following the instructions at the bottom of this blog entry. List<Product> coll = new List<Product>();Product prod; prod = new Product()  { ProductName = "From Zero to HTML 5 in 60 Minutes",     ProductId = 1 };coll.Add(prod);prod = new Product()   { ProductName = "Architecting Applications …",     ProductId = 2 };coll.Add(prod);prod = new Product()  { ProductName = "Introduction to Windows Phone Development",    ProductId = 3 };coll.Add(prod);prod = new Product()   { ProductName = "Architecting a Business  …",     ProductId = 4 };coll.Add(prod);......   Figure 1: Class without overriding ToString() Now, go back to the Product class and add an override of the ToString() method as shown in the code listed below: public class Product{  public string ProductName { get; set; }  public int ProductId { get; set; }   public override string ToString()  {    return ProductName;  }} In this simple sample, I am just returning the ProductName property. However, you can create a whole string of information if you wish to display more data in your data tips. Just concatenate any properties you want from your class and return that string. When you now run the application and hover over the collection object you will now see something that looks like Figure 2. Figure 2: Overriding ToString() in your Class Another place the ToString() override comes in handy is if you forget to use a DisplayMemberPath in your ListBox or ComboBox. The ToString() method is called automatically when a class is bound to a list control. Summary You should always override the ToString() method in your classes as this will help you when debugging your application. Seeing relevant data immediately in the data tip without having to drill down one more layer and maybe scroll through a complete list of properties should help speed up your development process. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “Override ToString” from the drop down list.  

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• (int) Math.floor(x / TILESIZE) or just (int) (x / TILESIZE)

  - by Aidan Mueller

  I have a Array that stores my map data and my Tiles are 64X64. Sometimes I need to convert from pixels to units of tiles. So I was doing: int x int y public void myFunction() { getTile((int) Math.floor(x / 64), (int) Math.floor(y / 64)).doOperation(); } But I discovered by using (I'm using java BTW) System.out.println((int) (1 / 1.5)) that converting to an int automatically rounds down. This means that I can replace the (int) Math.floor with just x / 64. But if I run this on a different OS do you think it might give a different result? I'm just afraid there might be some case where this would round up and not down. Should I keep doing it the way I was and maybe make a function like convert(int i) to make it easier? Or is it OK to just do x / 64?

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• Java int concurrency ++int equivalent to AtomicInteger.incrementAndGet()?

  - by Finbarr

  Are these two equivalent? In other words, are the ++ and -- operators atomic? int i = 0; return ++i; AtomicInteger ai = new AtomicInteger(0); return ai.incrementAndGet();

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• C# acting weird when reading in values from a file to an array

  - by Whitey

  This is the structure of my file: 1111111111111111111111111 2222222222222222222222222 3333333333333333333333333 4444444444444444444444444 5555555555555555555555555 6666666666666666666666666 7777777777777777777777777 8888888888888888888888888 9999999999999999999999999 0000000000000000000000000 0000000000000000000000000 0000000000000000000000000 0000000000000000000000000 0000000000000000000000000 And this is the code I'm using to read it into an array: using (StreamReader reader = new StreamReader(mapPath)) { string line; for (int i = 0; i < iMapHeight; i++) { if ((line = reader.ReadLine()) != null) { for (int j = 0; j < iMapWidth; j++) { iMap[i, j] = line[j]; } } } } I have done some debugging, and line[j] correctly iterates through each character in the currently read line. The problem lies with iMap[i, j]. After this block of code executes, this is the contents of iMap: - iMap {int[14, 25]} int[,] [0, 0] 49 int [0, 1] 49 int [0, 2] 49 int [0, 3] 49 int [0, 4] 49 int [0, 5] 49 int [0, 6] 49 int [0, 7] 49 int [0, 8] 49 int [0, 9] 49 int [0, 10] 49 int [0, 11] 49 int [0, 12] 49 int [0, 13] 49 int [0, 14] 49 int [0, 15] 49 int [0, 16] 49 int [0, 17] 49 int [0, 18] 49 int [0, 19] 49 int [0, 20] 49 int [0, 21] 49 int [0, 22] 49 int [0, 23] 49 int [0, 24] 49 int [1, 0] 50 int [1, 1] 50 int [1, 2] 50 int [1, 3] 50 int [1, 4] 50 int [1, 5] 50 int [1, 6] 50 int [1, 7] 50 int [1, 8] 50 int [1, 9] 50 int [1, 10] 50 int [1, 11] 50 int [1, 12] 50 int [1, 13] 50 int [1, 14] 50 int [1, 15] 50 int [1, 16] 50 int [1, 17] 50 int [1, 18] 50 int [1, 19] 50 int [1, 20] 50 int [1, 21] 50 int [1, 22] 50 int [1, 23] 50 int [1, 24] 50 int [2, 0] 51 int [2, 1] 51 int [2, 2] 51 int [2, 3] 51 int [2, 4] 51 int [2, 5] 51 int [2, 6] 51 int [2, 7] 51 int [2, 8] 51 int [2, 9] 51 int [2, 10] 51 int [2, 11] 51 int [2, 12] 51 int [2, 13] 51 int [2, 14] 51 int [2, 15] 51 int [2, 16] 51 int [2, 17] 51 int [2, 18] 51 int [2, 19] 51 int [2, 20] 51 int [2, 21] 51 int [2, 22] 51 int [2, 23] 51 int [2, 24] 51 int [3, 0] 52 int [3, 1] 52 int [3, 2] 52 int [3, 3] 52 int [3, 4] 52 int [3, 5] 52 int [3, 6] 52 int [3, 7] 52 int [3, 8] 52 int [3, 9] 52 int [3, 10] 52 int [3, 11] 52 int [3, 12] 52 int [3, 13] 52 int [3, 14] 52 int [3, 15] 52 int [3, 16] 52 int [3, 17] 52 int [3, 18] 52 int [3, 19] 52 int [3, 20] 52 int [3, 21] 52 int [3, 22] 52 int [3, 23] 52 int [3, 24] 52 int [4, 0] 53 int [4, 1] 53 int [4, 2] 53 int [4, 3] 53 int [4, 4] 53 int [4, 5] 53 int [4, 6] 53 int [4, 7] 53 int [4, 8] 53 int [4, 9] 53 int [4, 10] 53 int [4, 11] 53 int [4, 12] 53 int [4, 13] 53 int [4, 14] 53 int [4, 15] 53 int [4, 16] 53 int [4, 17] 53 int [4, 18] 53 int [4, 19] 53 int [4, 20] 53 int [4, 21] 53 int [4, 22] 53 int [4, 23] 53 int [4, 24] 53 int [5, 0] 54 int [5, 1] 54 int [5, 2] 54 int [5, 3] 54 int [5, 4] 54 int [5, 5] 54 int [5, 6] 54 int [5, 7] 54 int [5, 8] 54 int [5, 9] 54 int [5, 10] 54 int [5, 11] 54 int [5, 12] 54 int [5, 13] 54 int [5, 14] 54 int [5, 15] 54 int [5, 16] 54 int [5, 17] 54 int [5, 18] 54 int [5, 19] 54 int [5, 20] 54 int [5, 21] 54 int [5, 22] 54 int [5, 23] 54 int [5, 24] 54 int [6, 0] 55 int [6, 1] 55 int [6, 2] 55 int [6, 3] 55 int [6, 4] 55 int [6, 5] 55 int [6, 6] 55 int [6, 7] 55 int [6, 8] 55 int [6, 9] 55 int [6, 10] 55 int [6, 11] 55 int [6, 12] 55 int [6, 13] 55 int [6, 14] 55 int [6, 15] 55 int [6, 16] 55 int [6, 17] 55 int [6, 18] 55 int [6, 19] 55 int [6, 20] 55 int [6, 21] 55 int [6, 22] 55 int [6, 23] 55 int [6, 24] 55 int [7, 0] 56 int [7, 1] 56 int [7, 2] 56 int [7, 3] 56 int [7, 4] 56 int [7, 5] 56 int [7, 6] 56 int [7, 7] 56 int [7, 8] 56 int [7, 9] 56 int [7, 10] 56 int [7, 11] 56 int [7, 12] 56 int [7, 13] 56 int [7, 14] 56 int [7, 15] 56 int [7, 16] 56 int [7, 17] 56 int [7, 18] 56 int [7, 19] 56 int [7, 20] 56 int [7, 21] 56 int [7, 22] 56 int [7, 23] 56 int [7, 24] 56 int [8, 0] 57 int [8, 1] 57 int [8, 2] 57 int [8, 3] 57 int [8, 4] 57 int [8, 5] 57 int [8, 6] 57 int [8, 7] 57 int [8, 8] 57 int [8, 9] 57 int [8, 10] 57 int [8, 11] 57 int [8, 12] 57 int [8, 13] 57 int [8, 14] 57 int [8, 15] 57 int [8, 16] 57 int [8, 17] 57 int [8, 18] 57 int [8, 19] 57 int [8, 20] 57 int [8, 21] 57 int [8, 22] 57 int [8, 23] 57 int [8, 24] 57 int [9, 0] 48 int [9, 1] 48 int [9, 2] 48 int [9, 3] 48 int [9, 4] 48 int [9, 5] 48 int [9, 6] 48 int [9, 7] 48 int [9, 8] 48 int [9, 9] 48 int [9, 10] 48 int [9, 11] 48 int [9, 12] 48 int [9, 13] 48 int [9, 14] 48 int [9, 15] 48 int [9, 16] 48 int [9, 17] 48 int [9, 18] 48 int [9, 19] 48 int [9, 20] 48 int [9, 21] 48 int [9, 22] 48 int [9, 23] 48 int [9, 24] 48 int [10, 0] 48 int [10, 1] 48 int [10, 2] 48 int [10, 3] 48 int [10, 4] 48 int [10, 5] 48 int [10, 6] 48 int [10, 7] 48 int [10, 8] 48 int [10, 9] 48 int [10, 10] 48 int [10, 11] 48 int [10, 12] 48 int [10, 13] 48 int [10, 14] 48 int [10, 15] 48 int [10, 16] 48 int [10, 17] 48 int [10, 18] 48 int [10, 19] 48 int [10, 20] 48 int [10, 21] 48 int [10, 22] 48 int [10, 23] 48 int [10, 24] 48 int [11, 0] 48 int [11, 1] 48 int [11, 2] 48 int [11, 3] 48 int [11, 4] 48 int [11, 5] 48 int [11, 6] 48 int [11, 7] 48 int [11, 8] 48 int [11, 9] 48 int [11, 10] 48 int [11, 11] 48 int [11, 12] 48 int [11, 13] 48 int [11, 14] 48 int [11, 15] 48 int [11, 16] 48 int [11, 17] 48 int [11, 18] 48 int [11, 19] 48 int [11, 20] 48 int [11, 21] 48 int [11, 22] 48 int [11, 23] 48 int [11, 24] 48 int [12, 0] 48 int [12, 1] 48 int [12, 2] 48 int [12, 3] 48 int [12, 4] 48 int [12, 5] 48 int [12, 6] 48 int [12, 7] 48 int [12, 8] 48 int [12, 9] 48 int [12, 10] 48 int [12, 11] 48 int [12, 12] 48 int [12, 13] 48 int [12, 14] 48 int [12, 15] 48 int [12, 16] 48 int [12, 17] 48 int [12, 18] 48 int [12, 19] 48 int [12, 20] 48 int [12, 21] 48 int [12, 22] 48 int [12, 23] 48 int [12, 24] 48 int [13, 0] 48 int [13, 1] 48 int [13, 2] 48 int [13, 3] 48 int [13, 4] 48 int [13, 5] 48 int [13, 6] 48 int [13, 7] 48 int [13, 8] 48 int [13, 9] 48 int [13, 10] 48 int [13, 11] 48 int [13, 12] 48 int [13, 13] 48 int [13, 14] 48 int [13, 15] 48 int [13, 16] 48 int [13, 17] 48 int [13, 18] 48 int [13, 19] 48 int [13, 20] 48 int [13, 21] 48 int [13, 22] 48 int [13, 23] 48 int [13, 24] 48 int Sorry for the lame formatting, but it's huge :P I have no idea where it's getting these values from, does anyone have an explanation? Thanks :)

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• Understanding C# async / await (1) Compilation

  - by Dixin

  Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is called MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been cleaned up so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# level syntax sugar. There is no difference to await a async method or a normal method. A method returning Task will be awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } The above code is already cleaned up, but there are still a lot of things. More clean up can be done, and the state machine can be very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> void IAsyncStateMachine.MoveNext() { try { switch (this.State) { // Orginal code is splitted by "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; IAsyncStateMachine this1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this1.MoveNext()); // Callback break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; IAsyncStateMachine this2 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this2.MoveNext()); // Callback break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync_(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; (multiCallMethodAsyncStateMachine as IAsyncStateMachine).MoveNext(); // Original code are in this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clear - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback Since it is about callback, the simplification  can go even further – the entire state machine can be completely purged. Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is literally pretending to wait. In a await expression, a Task object will be return immediately so that caller is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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• Understanding C# async / await (1) Compilation

  - by Dixin

  Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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• 100.toString vs 100['toString']

  - by dorelal

  100['toString'] //does not fail 100.toString //fails why? 100.toString is not same as 100.toString() . So why in the second case I am not getting the function as returned value?

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• which toString() method can be used performance wise??

  - by Mrityunjay

  hi, I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :- public String toString() { return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name; } public String toString() { StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return buff.toString(); } public String toString() { StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return builder .toString(); } can anyone please help me to find out which one is best and should be used for enhancing performance.

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• Should I redesign my code when collegues says so?

  - by Kirill V. Lyadvinsky

  I wrote a function recently that finds maximum of two ints. Here is a code: int get_max (int(*a)(int(*)(int(*)()),int(*)(int(*)(int**))), int(*b)(int(*) (int(*)()),int*,int(*)(int(*)()))){return (int)((((int(*)(int(*)(int(*)()),int( *)(int(*)())))a)> ((int(*)(int(*)(int(*)()),int(*)(int(*)())))b))?((int(*)( int(*)(int(*)()),int(*)(int(*)())))a):((int(*)(int(*)(int(*)()),int(*)(int(*)( ))))b));} int main() { int x = get_max( (int(*)(int(*)(int(*)()),int(*)(int(*)(int**)))) 500, (int(*)(int(*)(int(*)()),int*,int(*)(int(*)()))) 100 ); cout << x << endl; // prints 500 as expected return 0; } It works fine, but my collegue says that I shouldn't use C style casts. But I think that all that modern static_cast's and reinterpret_cast's will make my code too cumbersome. Who's right? Should I redesign my code using C++ style casts or original code is OK?

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• what is the difference between const int*, const int * const, int const *

  - by ultraman

  I always mess up how to use it correctly. Is there a set of rules defining what you can and cannot do? I want to know all the Do's and all DoNOTs in terms of assignments, passing to the functions, etc. Thanks

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• Invalid conversion from int to int

  - by FOXMULDERIZE

  #include <iostream> #include<fstream> using namespace std; void showvalues(int,int,int []); void showvalues2(int,int); void sumtotal(int,int); int main() { const int SIZE_A= 9; int arreglo[SIZE_A]; ifstream archivo_de_entrada; archivo_de_entrada.open("numeros.txt"); int count,suma,total,a,b,c,d,e,f; int total1=0; int total2=0; //lee/// for(count =0 ;count < SIZE_A;count++) archivo_de_entrada>>arreglo[count] ; archivo_de_entrada.close(); showvalues(0,3,9); HERE IS THE PROBLEM showvalues2(5,8); sumtotal(total1,total2); system("pause"); return 0; } void showvalues(int a,int b,int v) { //muestra//////////////////////// cout<< "los num son "; for(count = a ;count <= b;count++) total1 = total1 + arreglo[count]; cout <<total1<<" "; cout <<endl; } void showvalues2(int c,int d) { ////////////////////////////// cout<< "los num 2 son "; for(count =5 ;count <=8;count++) total2 = total2 + arreglo[count]; cout <<total2<<" "; cout <<endl; } void sumtotal(int e,int f) { ///////////////////////////////// cout<<"la suma de t1 y t2 es "; total= total1 + total2; cout<<total; cout <<endl; }

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• BigInteger.ToString() returns more than 50 decimal digits.

  - by brickner

  I'm using .NET 4 System.Numerics.BigInteger Structure and I'm getting results different from the documentation. In the documentation of BigInteger.ToString() Method It says: The ToString() method supports 50 decimal digits of precision. That is, if the BigInteger value has more than 50 digits, only the 50 most significant digits are preserved in the output string; all other digits are replaced with zeros. I have some code that takes a 60 decimal digits BigInteger and converts it to a string. The 60 significant decimal digits string didn't lose any significant digits: const string vString = "123456789012345678901234567890123456789012345678901234567890"; Assert.AreEqual(60, vString.Length); BigInteger v = BigInteger.Parse(vString); Assert.AreEqual(60, v.ToString().Length); Assert.AreEqual('9', v.ToString()[58]); Assert.AreEqual('1', v.ToString()[0]); Assert.AreEqual(vString, v.ToString()); All the asserts pass. What exactly does the quoted part of the documentation mean?

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• Auto-generating toString Method

  - by Gordon

  Is it good or bad practice auto-generating toString methods for some simple classes? I was thinking of generating something like bellow where it takes the variable names and produces a toString method that prints the name followed by it's value. private String name; private int age; private double height; public String toString(){ Formatter formatter = new Formatter(); return formatter.format("Name: %s, Age: %d, Height %f", name, age, height).toString(); }

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• Difference between Convert.ToString Method and Object.ToString() with regard to Globalization

  - by Ananth

  Is there any difference between Convert.ToString Method and Object.ToString() in C#.net other than the how these handle null value. There could be some difference between the two in the Globalization Perspective.

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• Difference between Convert.tostring() and .tostring()

  - by Ayyappan.Anbalagan

  Difference between Convert.tostring() and .tostring(). I got many difference in web.But what is major reason?

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• convert ArrayList.toString() back to ArrayList in one call

  - by dotnetnewbie

  I have a toString() representation of an ArrayList. Copying the toString() value to clipboard, I want to copy it back into my IDE editor, and create the ArrayList instance in one line. In fact, what I'm really doing is this: my ArrayList.toString() has data I need to setup a unit test. I want to copy this ArrayList.toString() into my editor to build a test against this edge case I don't want to parse anything by hand My input looks like this: [15.82, 15.870000000000001, 15.92, 16.32, 16.32, 16.32, 16.32, 17.05, 17.05, 17.05, 17.05, 18.29, 18.29, 19.16] The following do not work: Arrays.asList() google collections Lists.newArrayList() Suggestions?

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• toString method for varargs contructor

  - by owca

  I have a varargs contructor like this : public class Sentence { public String[] str; public Sentence(Object... text){ StringBuilder sb = new StringBuilder(); for (Object o : text) { sb.append(o.toString()) .append(" "); } System.out.println(sb.toString()); } } Contructor can get various types of data (ints, strings, and Sentence objects as well). How to do a proper toString method for such class ?

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• Is ToString() optimized by compiler?

  - by TheVillageIdiot

  Suppose I've following Code: Console.WriteLine("Value1: " + SomeEnum.Value1.ToString() + "\r\nValue2: " + SomeOtherEnum.Value2.ToString()); Will Compiler Optimize this to: Console.WriteLine("Value1: " + SomeEnum.Value1 + "\r\nValue2: " + SomeOtherEnum.Value2); I've checked it with IL Disassembler and there are calls to IL_005a: callvirt instance string [mscorlib]System.Object::ToString() I don't know if JIT optimizes this.

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• document.getElementById in toString

  - by KooiInc

  edit Found my answers here. Bottom line: toString/valueOf can only return primitive types. So here the lack of native getters in javascript shows, I suppose. I would like to use the following simple function in an elementwrapper: function ElGetter(id){ var id = id; return { set: function(nwid){id = nwid;}, toString: function(){return document.getElementById(id);}, valueOf: function(){return document.getElementById(id);} }; } var myEl = ElGetter('myId'); console.log(myEl.innerHTML); //=> undefined But I can't get it to work. Is it a DOM/javascript restriction or am I missing something? Normally it works, as in: function Tester(){ var x = 1; return { toString: function(){return x}, valueOf: function(){return x} } } var myTest = Tester(); console.log(myTest); //=> 1

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• JavaScript using toString on a Function object to read text content

  - by mseeley

  Calling toString() on the function below returns different strings across browsers. I understand this is because ECMA-262 15.3.4.2 leaves wiggle room for each vendor. Chrome returns the comments in addition to all syntax. Sadly Firefox 3.6 omits the comments. Based on Firefox's behavior I haven't tested IE, Opera, or Safari. function foo() { /* comment */ var bar = true; } Specifically, I am attempting to embed meta data within a specially formatted comment block within a function. Later the return value of the functions toString() method would be parsed and values returned as an object. I've been unable to locate compatibility tables or alternatives to toString(). Does the community have any ideas? Btw, pre-processing JS files isn't an option. :( Thanks a lot. :)

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• Why Is ToString() Rounding My Double Value?

  - by user163757

  How do I prevent my double value from being rounded when converting to a string? I have tried both Convert.ToString and ToString() with the same result. For example my double may look something like 77.987654321, and the two strings conversions convert to to 77.98765. I need to keep the precision of the value as is.

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• java.util.Date.toString() is printing out wrong format

  - by pacoverflow

  The following code prints out "vmtDataOrig.creationdate=2012-11-03" VmtData vmtDataOrig = VmtDataDao.getInstance().loadVmt(1); System.out.println("vmtDataOrig.creationdate=" + vmtDataOrig.getCreationDate().toString()); Here is the definition of the creationDate field in the VmtData class: private Date creationDate = null; Here is the hibernate mapping of the creationDate field to the database table column: <property name="creationDate" column="CREATIONDATE" type="date"/> The CREATIONDATE column in the MySQL database table is of type "date", and for the record retrieved it has the value "2012-11-03". The Javadoc for the java.util.Date.toString() method says it is supposed to print the Date object in the form "dow mon dd hh:mm:ss zzz yyyy". Anyone know why it is printing it out in the form "yyyy-MM-dd"?

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• Given year, month and day, all in int, how would I generate an NSDate

  - by BU

  I think the solution is really simple, I just haven't come across it online. Suppose I am given int year, int month, int day, int hour, int min, int sec.. how do I generate NSDate out of it? I know we can use [NSDate initWithString:] but I think it gets complicated if month/day/hour/min/sec are one digit numbers. Thanks in advance for your help.

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• How to return a verbatim string from ConfigurationManager.AppSetting["settingname"].ToString()

  - by Josh H.

  I am using the ConfigurationManager.AppSetting["blah"].ToString() method to get the path to the folder that contains the files I'm needing. But I'm throwing an UnsupportedFormatException on the path when it tries to use Directory.GetFiles(path). The returning value has the escape characters included and I'm not sure how to keep it from returning the extra characters. This is what the path looks like after it is returned: \\\\\\\\C:\\\\folder1\\\\folder2

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