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  • c# im getting an error

    - by vj4u
    double dval = 1; for (int i = 0; i < Cols; i++) { k = 0; dval = 1; for (int j = Cols - 1; j >= 0; j--) { colIndex = (i + j) % 3; val *= dval[colIndex, k]; k++; } det -= dval; } im getting an error Cannot apply indexing with [] to an expression of type 'double' for dval help its urgent

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  • Haskell: Problems with overloading: Interpreter can´t tell which + to use

    - by Ben
    Hi, I want to make functions Double - Double an instance of the Num typeclass. I want to define the sum of two functions as sum of their images. So I wrote instance Num Function where f + g = (\ x - (f x) + (g x)) Here the compiler complains he can´t tell whether I´m using Prelude.+ or Module.+ in the lambda expression. So I imported Prelude qualified as P and wrote instance Num Function where f + g = (\ x - (f x) P.+ (g x)) This compiles just fine, but when I try to add two functions in GHCi the interpreter complains again he can´t tell whether I´m using Prelude.+ or Module.+. Is there any way I can solve this problem?

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  • What's the deal with char.GetNumericValue?

    - by mgroves
    I was working on Project Euler 40, and was a bit bothered that there was no int.Parse(char). Not a big deal, but I did some asking around and someone suggested char.GetNumericValue. GetNumericValue seems like a very odd method to me: Takes in a char as a parameter and returns...a double? Returns -1.0 if the char is not '0' through '9' So what's the reasoning behind this method, and what purpose does returning a double serve? I even fired up Reflector and looked at InternalGetNumericValue, but it's just like watching Lost: every answer just leads to another question.

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  • iPhone SKD make the iPod controller appear

    - by nico
    Hi all, It's been a while I'm consulting stackoverflow, but this time I didn't find any answer :( My question is quite simple :) On an iPhone/iPod touch, play music. Double tap the home button while the music is playing. You will see appear a popup with the play/pause/next/previous buttons and a volume control. Do you know if it's possible to make this popup appear programmatically ? I mean, I would like to add a button in my app that will display the popup, avoiding the user to double tap the home button (most of them doesn't know this shortcut). Thank you in advance !

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  • .Net Round-trip Types

    - by Fujiy
    I making a method that generate a unique string key for some parameters. But the same key if call with same values. I just accept primitive types, string, DateTime, Guid, and Nullable(since I append types together, I can distinguish who is int and who is int?), because I can convert all to string without lost values or precision.(for float and double a use ToString("R"), to DateTime ToString("O")). Exists a easy way to know which types I can transform in strings without conflict? And how do this transform(how I said before, float, double and datetime have specific ways) Thanks

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  • How to use the boost lexical_cast library for just for checking input

    - by Inverse
    I use the boost lexical_cast library for parsing text data into numeric values quite often. In several situations however, I only need to check if values are numeric; I don't actually need or use the conversion. So, I was thinking about writing a simple function to test if a string is a double: template<typename T> bool is_double(const T& s) { try { boost::lexical_cast<double>(s); return true; } catch (...) { return false; } } My question is, are there any optimizing compilers that would drop out the lexical_cast here since I never actually use the value? Is there a better technique to use the lexical_cast library to perform input checking?

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  • Dynamic creation of a pointer function in c++

    - by Liberalkid
    I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?

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  • is there a way to remove duplication in this code

    - by oo
    i have a method that looks like this: private double GetX() { if (Servings.Count > 0) { return Servings[0].X; } if (!string.IsNullOrEmpty(Description)) { FoodDescriptionParser parser = new FoodDescriptionParser(); return parser.Parse(Description).X; } return 0; } and i have another method that looks like this: private double GetY() { if (Servings.Count > 0) { return Servings[0].Y; } if (!string.IsNullOrEmpty(Description)) { FoodDescriptionParser parser = new FoodDescriptionParser(); return parser.Parse(Description).Y; } return 0; } is there anyway to consolidate this as the only thing different is the property names?

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  • Illegal Start of Expression

    - by Kraivyne
    Hello there, I have just started to learn the very basics of Java programming. Using a book entitled "Programming Video Games for the Evil Genius". I have had an Illegal Start of Expression error that I can't for the life of me get rid of. I have checked the sample code from the book and mine is identical. The error is coming from the for(int i = difficulty; i = 0; i- - ) line. Thanks for helping a newbie out. import javax.swing.*; public class S1P4 {public static void main(String[] args) throws Exception { int difficulty; difficulty = Integer.parseInt(JOptionPane.showInputDialog("How good are you?\n"+ "1 = Great\n"+"10 = Terrible")); boolean cont = false; do { cont = false; double num1 = (int)(Math.round(Math.random()*10)); double num2; do { num2 = (int)(Math.round(Math.random()*10)); } while(num2==0.0); int sign = (int)(Math.round(Math.random()*3)); double answer; System.out.println("\n\n*****"); if(sign==0) { System.out.println(num1+" times "+num2); answer = num1*num2; } else if(sign==1) { System.out.println(num1+" divided by"+num2); answer = num1/num2; } else if(sign==1) { System.out.println(num1+" plus "+num2); answer = num1+num2; } else if(sign==1) { System.out.println(num1+" minus "+num2); answer = num1-num2; } else { System.out.println(num1+" % "+num2); answer = num1%num2; } System.out.println("*****\n"); for(int i = difficulty; i >= 0; i- - ) { System.out.println(i+"..."); Thread.sleep(500); } System.out.println("ANSWER: "+answer); String again; again = JOptionPane.showInputDialog("Play again?"); if(again.equals("yes")) cont = true; } while(cont); } }

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  • Avoid Flickering in Windows Forms?

    - by user1733909
    Double buffering not working with combo-box. is there any another methods to avoid flickering in windows forms? i have one windows form with number of panels in it. I'm showing only one panel at a time based on my menu selection. i have one icon panel,one header panel and the combo box. based on the selected item of that combo-box the gridview1 and 2 are filling. when I'm rapidly selecting the combo-box item using my keyboard down arrow the icon panel and the header panel are always repainting. i need to keep that both without any change. this two panels producing some flashing effect(ie,they are blinking or flashing) while I'm changing the combo box selected index. is there any way to avoid this flashing.? i tried double-buffered enabled in form constructor and form load event. Please Help..............

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  • Controling the visibility of a Bitmap in .NET

    - by ET
    Hi everyone, I am trying to create this simple application in c#: when the user double clicks on specific location in the form, a little circle will be drawn. By one click, if the current location is marked by a circle - the circle will be removed. I am trying to do this by simply register the MouseDoubleClick and MouseClick events, and to draw the circle from a .bmp file the following way: private void MouseDoubleClick (object sender, MouseEventArgs e) { Graphics g = this.CreateGraphics(); Bitmap myImage = (Bitmap)Bitmap.FromFile("Circle.bmp"); g.DrawImage(myImage, e.X, e.Y); } My problem is that I dont know how to make the circle unvisible when the user clicks its location: I know how to check if the selected location contains a circle (by managing a list of all the locations containig circles...), but I dont know how exactly to delete it. Another question: should I call the method this.CreateGraphics() everytime the user double-clicks a location, as I wrote in my code snippet, or should I call it once on initialization?

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  • Could someone explain __declspec(naked) please?

    - by Scott
    I'm looking into porting a script engine written for Windows to Linux; it's for Winamp's visualization platform AVS. I'm not sure if it's even possible at the moment. From what I can tell the code is taking the addresses of the C functions nseel_asm_atan and nseel_asm_atan_end and storing them inside a table that it can reference during code execution. I've looked at MS's documentation, but I'm unsure what __declspec(naked) really does. What is prolog and epilog code mentioned in the documentation? Is that related to Windows calling conventions? Is this portable? Know of any Linux-based examples using similar techniques? static double (*__atan)(double) = &atan; __declspec ( naked ) void nseel_asm_atan(void) { FUNC1_ENTER *__nextBlock = __atan(*parm_a); FUNC_LEAVE } __declspec ( naked ) void nseel_asm_atan_end(void) {}

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  • NoSuchMethodException while using JAVA Reflection

    - by Appps
    Hi I'm trying to use reflection to invoke a method and update the setter value of that method. But I'm getting NoSuchMethodException while ivoking that method. com.test.Test.setAddress1(java.lang.Double) .But I've this method defined in my Class. Is the problem with my code. Can someone please help me? Thanks in advance. I've my code below. Class[] doubleArrayParamTypes = new Class[ 1 ]; doubleArrayParamTypes[ 0 ] = Double.class; Class class=Class.forName( "com.test.Test"); Object voObject = class.newInstance(); String data="TestData"; performMapping(class,"setAddress1",doubleArrayParamTypes ,voObject,data); /* Reflection to set the data */ private void performMapping(Class class,String methodName,Class[] clazz,Object voObject,Object data) { class.getMethod( "set" + methodName, clazz ).invoke( voObject, data ); }

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  • Importing CSV with line breaks in Excel 2007

    - by ph0enix
    I'm working on a feature to export search results to a CSV file to be opened in Excel. One of the fields is a free-text field, which may contain line breaks, commas, quotations, etc. In order to counteract this, I have wrapped the field in double quotes ("). However, when I import the data into Excel 2007, set the appropriate delimiter, and set the text qualifier to double quote, the line breaks are still creating new records at the line breaks, where I would expect to see the entire text field in a single cell. I've also tried replacing CR/LF (\r\n) with just CR (\r), and again with just LF (\n), but no luck. Has anyone else encountered this behavior, and if so, how did you fix it? TIA, -J

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  • Member variable in C++ class that is always constant for all objects of that class?

    - by user1799323
    I'm constructing a class where I have three member variables that I want to always be the same value NO MATTER WHAT. I have class foo{ public: double var_1, var_2, var_3; double x=1, y=2, z=3; [functions go here] }; that gave me an error since I can't initialize a variable like that. But I want x, y and z to always be 1, 2 and 3 respectively. I tried defining them outside the class but that doesn't work since I want them to be member variables of the class. How do I do this?

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  • STL: how to overload operator= for <vector> ?

    - by MBes
    There's simple example: #include <vector> int main() { vector<int> veci; vector<double> vecd; for(int i = 0;i<10;++i){ veci.push_back(i); vecd.push_back(i); } vecd = veci; // <- THE PROBLEM } The thing I need to know is how to overload operator = so that I could make assignment like this: vector<double> = vector<int>; I've just tried a lot of ways, but always compiler has been returning errors... Is there any option to make this code work without changing it? I can write some additional lines, but can't edit or delete the existing ones. Ty.

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  • Solving C++ 'target of assignment not really an lvalue' errors

    - by Jason
    Given this code: void FrMemCopy(void *to, const void *from, size_t sz) { size_t sz8 = sz >> 3; size_t sz1 = sz - (sz8 << 3); while (sz8-- != 0) { *((double *)to)++ = *((double *)from)++; } while (sz1-- != 0) { *((char *)to)++ = *((char *)from)++; } } I am receiving target of assignment not really an lvalue warnings on the 2 lines inside the while loops. Can anyone break down those lines? a cast then an increment? What is a simplier way to write that? What does the error mean?

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  • Java: empty ArrayLists in a foor loop

    - by Patrick
    hi, I'm reusing the same ArrayList in a for loop, and I use for loop results = new ArrayList<Integer>(); experts = new ArrayList<Integer>(); output = new ArrayList<String>(); .... to create new ones. I guess this is wrong, because I'm allocating new memory. Is this correct ? If yes, how can I empty them ? Added: another example I'm creating new variables each time I call this method. Is this good practice ? I mean to create new precision, relevantFound.. etc ? Or should I declare them in my class, outside the method to not allocate more and more memory ? public static void computeMAP(ArrayList results, ArrayList experts) { //compute MAP double precision = 0; int relevantFound = 0; double sumprecision = 0; thanks

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  • Which database should I use for best performance

    - by _simon_
    Hello, I am working in Visual Studio 2005, .NET 2.0. I need to write an application, which listens on COM port and saves incoming data to a database. Main feature: save incoming data (series of 13-digits numbers), if this number allready exists, then mark it as double. For example, there could be these records in database: 0000000000001 OK 0000000000002 OK 0000000000002 Double 0000000000003 OK 0000000000004 OK I could use SQL database, but I don't know if it is fast enough... Database should be able to store up to 10.000.000 records and write up to 100 records per minute (so it needs to check 100 times per minute if this record allready exists). Which database should I use? Maybe the whole database would need to be in RAM. Where could I learn more about this? Thanks

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  • Segmentation fault C++ in recursive function

    - by user69514
    Why do I get a segmentation fault in my recursive function. It happens every time i call it when a value greater than 4 as a parameter #include <iostream> #include <limits> using namespace std; int printSeries(int n){ if(n==1){ return 1; } else if( n==2){ return 2; } else if( n==3){ return 3; } else if( n==4){ return printSeries(1) + printSeries(2) + printSeries(3); } else{ return printSeries(n-3) + printSeries((n-2) + printSeries(n-1)); } } int main(){ //double infinity = numeric_limits<double>::max(); for(int i=1; i<=10; i++){ cout << printSeries(i) << endl; } return 0; }

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  • LINQ Expression help with Func TEntity,TType

    - by Chris Conway
    I have a repository method that accepts an order by parameter in the form: public IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity,string>> orderBy) Now that works fine when trying to sort by a property of type string, var entities = rep.Get(x => x.Name); but what if i want to sort by double or int or any other type. Doing something like var entities = rep.Get(x => x.Price); obviously throws a compile error saying I can't convert double to string. How can I make this more generic so I can sort by any property in my entity, or at least the properties where the type implements IComparable or something similar?

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  • No warning from gcc when function definition in linked source different from function prototype in h

    - by c_c
    Hi, I had a problem with a part of my code, which after some iterations seemed to read NaN as value of a int of a struct. I think I found the error, but am still wondering why gcc (version 3.2.3 on a embedded Linux with busybox) did not warn me. Here are the important parts of the code: A c file and its header for functions to acquire data over USB: // usb_control.h typedef struct{ double mean; short *values; } DATA_POINTS; typedef struct{ int size; DATA_POINTS *channel1; //....7 more channels } DATA_STRUCT; DATA_STRUCT *create_data_struct(int N); // N values per channel int free_data_struct(DATA_STRUCT *data); int aqcu_data(DATA_STRUCT *data, int N); A c and header file with helper function (math, bitshift,etc...): // helper.h int mean(DATA_STRUCT *data); // helper.c (this is where the error is obviously) double mean(DATA_STRUCT *data) { // sum in for loop data->channel1->mean = sum/data->N; // ...7 more channels // a printf here displayed the mean values corretly } The main file // main.c #include "helper.h" #include "usb_control.h" // Allocate space for data struct DATA_STRUCT *data = create_data_struct(N); // get data for different delays for (delay = 0; delay < 500; delay += pw){ acqu_data(data, N); mean(data); // printf of the mean values first is correct. Than after 5 iterations // it is always NaN for channel1. The other channels are displayed correctly; } There were no segfaults nor any other missbehavior, just the NaN for channel1 in the main file. After finding the error, which was not easy, it was of course east to fix. The return type of mean(){} was wrong in the definition. Instead of double mean() it has to be int mean() as the prototype defines. When all the functions are put into one file, gcc warns me that there is a redefinition of the function mean(). But as I compile each c file seperately and link them afterwards gcc seems to miss that. So my questions would be. Why didn't I get any warnings, even non with gcc -Wall? Or is there still another error hidden which is just not causing problems now? Regards, christian

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