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  • Is the old vector get cleared? If yes, how and when?

    - by user180866
    I have the following code: void foo() { vector<double> v(100,1); // line 1 // some code v = vector<double>(200,2); // line 2 // some code } what happened to the vector of size 100 after the second line? Is it gets cleared by itself? If the answer is yes, how and when it is cleared? By the way, is there any other "easy and clean" ways to change the vector as in line 2? I don't want things like v.resize(200); for (int i=0; i<200; i++) v[i] = 2;

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  • usage of 2 charectors in single qoutes in c

    - by user1632141
    #include<stdio.h> int main() { char ch = 'A'; printf("%d\n",'ag'); printf("%d\n",'a'); printf("%d, %d, %d, %d", sizeof(ch), sizeof('a'), sizeof('Ag'), sizeof(3.14f)); return 0; } I used to have many doubts on the output of this question while running on g++ and gcc. But I have cleared almost all the doubts by referring these links: Single and double quotes in C/C++ Single quotes vs. double quotes in C I still need to understand one thing about the output of this question. Can someone please explain the output of printf("%d\n",'ag'); mentioned above in the program. How is it actually stored in the memory? The output for the program on the Linux/GCC platform is: 24935 97 1, 4, 4, 4

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  • Incompatible Types in Initialization

    - by jack
    I have the following code in a subroutine that produces an incompatible types in initialization error on the varVal library in the subroutine evaluateExpression: NSDictionary *varVal; for (int i=0; i<varCount; i++) { [varVal setObject:[(i+1)*2 stringValue] forKey:[i stringValue]]; } double result =[[self brain] evaluateExpression:[[self brain] expression] usingVariableValues:varVal]; My subroutine declaration in the brain.h file is: +(double)evaluateExpression:(id)anExpression usingVariableValues:(NSDictionary *)variables; I'd appreciate any help.

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  • Controlling 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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  • C: using clock() to measure time in multi-threaded programs

    - by Shinka
    I've always used clock() to measure how much time my application took from start to finish, as; int main(int argc, char *argv[]) { const clock_t START = clock(); // ... const double T_ELAPSED = (double)(clock() - START) / CLOCKS_PER_SEC; } Since I've started using POSIX threads this seem to fail. It looks like clock() increases N times faster with N threads. As I don't know how many threads are going to be running simultaneously, this approach fails. So how can I measure how much time has passed ?

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  • error unidentfied identfier "exams" and i dont know why in c++

    - by user320950
    // basic file operations #include <iostream> #include <fstream> using namespace std; void read_file_in_array(int exam[100][3]); double calculate_total(int exam1[], int exam2[], int exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); int main() { int go,go2,go3; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; }/* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(int exam1[],int exam2[],int exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam1[i] <=90 && exam1[i] >=100) { above90++; cout << above90; } } return exam3[i]; } void read_file_in_array(double exam[100][3]) { ifstream infile; int num, i=0,j=0; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); }

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  • Efficiency: Creating an array of doubles incrementally?

    - by Alan
    Consider the following code: List<double> l = new List<double>(); //add unknown number of values to the list l.Add(0.1); //assume we don't have these values ahead of time. l.Add(0.11); l.Add(0.1); l.ToArray(); //ultimately we want an array of doubles Anything wrong with this approach? Is there a more appropriate way to build an array, without knowing the size, or elements ahead of time?

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  • Some issue with bufferedReader

    - by thetna
    I have a java function as follows: public HashMap<String, ArrayList<Double>> embedWords(BufferedReader buffR1 { ArrayList<String > arrayList = new ArrayList<String>(); arrayList = getWords(buffR1); System.out.println("Word size:"+ arrayList.size()); ArrayList<ArrayList<Double>> arrList = getWordFeature(buffR1); System.out.println("Size of arrList:embedWords:"+arrList.size()); } Here , the problem is , the both of the function getWords and getWordFeatures can't give the size value. When i comment function getWords the function getWordFeature returns non-zero value .But when uncommented , the output is as follows: Word size:15055 Size of arrList:embedWords: 0

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  • Why does casting a NaN to a long yeild a valid result?

    - by brainimus
    In the sample code below I am dividing by zero which when I step through it with the debugger the (dividend / divisor) yeilds an Infinity or NaN (if the divisor is zero). When I cast this result to a long I get a valid result, usually something like -9223372036854775808. Why is this cast valid? Why doesn't it stop executing (throw an exception for example) rather than assign an arbitrary value? double divisor = 0; double dividend = 7; long result = (long)(dividend / divisor);

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  • Function declaration in C and C++

    - by Happy Mittal
    I have two C++ files, say file1.cpp and file2.cpp as //file1.cpp #include<cstdio> void fun(int i) { printf("%d\n",i); } //file2.cpp void fun(double); int main() { fun(5); } When I compile them and link them as c++ files, I get an error "undefined reference to fun(double)". But when I do this as C files, I don't get error and 0 is printed instead of 5. Please explain the reason. Moreover I want to ask whether we need to declare a function before defining it because I haven't declared it in file1.cpp but no error comes in compilation.

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  • C++ integer floor function

    - by Thomas
    I want to implement greatest integer function. int x = 5/3; My question is with greater numbers could there be a loss of precision as 5/3 would produce a double? EDIT: Greatest integer function is integer less than or equal to X. Example: 4.5 = 4 4 = 4 3.2 = 3 3 = 3 What I want to know is 5/3 going to produce a double? Because if so I will have loss of precision when converting to int. Hope this makes sense. RE-EDIT: What OP calls 'greatest integer' most of us call 'floor'.

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  • Rounding a positive number to a power of another number

    - by Sagekilla
    I'm trying to round a number to the next smallest power of another number. The number I'm trying to round is always positive. I'm not particular on which direction it rounds, but I prefer downwards if possible. I would like to be able to round towards arbitrary bases, but the ones I'm most concerned with at the moment is base 2 and fractional powers of 2 like 2^(1/2), 2^(1/4), and so forth. Here's my current algorithm for base 2. The log2 I multiply by is actually the inverse of log2: double roundBaseTwo(double x) { return 1.0 / (1 << (int)((log(x) * log2)) } Any help would be appreciated!

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  • Matrix multiplication using Matrix Template library (MTL 4)

    - by Lxc
    The program is as following: #include <iostream> #include <boost/numeric/mtl/mtl.hpp> using namespace mtl; int main(int argc, char* argv[]) { dense_vector<double> a(5,1.0); dense_vector<double> b(5,2.0); a * trans(b); } I want to calculate a * trans(b), but there is a compling error :C2893. Will someone help me? Thanks a lot!

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  • What's wrong with this addProximity code?

    - by Pentium10
    I have this code: private void setupProximity() { Intent intent = new Intent(this, viewContacts.class); PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, 0); LocationUtils.addProximity(this, -37.40, 144.55, 1000, 1000000, sender); } public static void addProximity(Context ctx,double lat, double lon, float rad,long exp, PendingIntent pintent) { LocationManager lm = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE); lm.addProximityAlert(lat, lon, rad, exp, pintent); } Why I don't get the class to fire up? I am in the range of the zone.

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • C# / IronPython Interop and the "float" data type

    - by Adam Haile
    Working on a project that uses some IronPython scripts to as plug-ins, that utilize functionality coded in C#. In one of my C# classes, I have a property that is of type: Dictionary<int, float> I set the value of that property from the IronPython code, like this: mc = MyClass() mc.ValueDictionary = Dictionary[int, float]({1:0.0, 2:0.012, 3:0.024}) However, when this bit of code is run, it throws the following exception: Microsoft.Scripting.ArgumentTypeException was unhandled by user code Message=expected Dictionary[int, Single], got Dictionary[int, float] To make things weirder, originally the C# code used Dictionary<int, double> but I could not find a "double" type in IronPython, tried "float" on a whim and it worked fine, giving no errors. But now that it's using float on both ends (which it should have been using from the start) it errors, and thinks that the C# code is using the "Single" data type?! I've even checked in the object browser for the C# library and, sure enough, it shows as using a "float" type and not "Single"

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  • Unsigneds in order to prevent negative numbers

    - by Bruno Brant
    let's rope I can make this non-sujective Here's the thing: Sometimes, on fixed-typed languages, I restrict input on methods and functions to positive numbers by using the unsigned types, like unsigned int or unsigned double, etc. Most libraries, however, doesn't seem to think that way. Take C# string.Length. It's a integer, even though it can never be negative. Same goes for C/C++: sqrt input is an int or a double. I know there are reasons for this ... for example your argument might be read from a file and (no idea why) you may prefer to send the value directly to the function and check for errors latter (or use a try-catch block). So, I'm assuming that libraries are way better designed than my own code. So what are the reasons against using unsigned numbers to represent positive numbers? It's because of overflow when we cast then back to signed types?

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  • Add up values from a text file

    - by Stanley
    Hi Guys I have a text file that contains Amounts at Substring (34, 47) of each line. I need to sum Up all the Values to the End of the File. I have this code that I had started to build but I do not know how to proceed from here: public class Addup { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException, IOException { // TODO code application logic here FileInputStream fs = new FileInputStream("C:/Analysis/RL004.TXT"); BufferedReader br = new BufferedReader(new InputStreamReader(fs)); String line; while((line = br.readLine()) != null){ String num = line.substring(34, 47); double i = Double.parseDouble(num); System.out.println(i); } } } The output is like this: 1.44576457E4 2.33434354E6 4.56875685E3 The Amount is in two decimal Places and I need the result also in the Two decimal Places. What Is the Best way to achieve this?

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  • How can i use listDictionary?

    - by Phsika
    i can fill my listdictinary but, if running error returns to me in " foreach (string ky in ld.Keys)"(invalid operation Exception was unhandled) Error Detail : After creating a pointer to the list of sample collection has been changed. C# ListDictionary ld = new ListDictionary(); foreach (DataColumn dc in dTable.Columns) { MessageBox.Show(dTable.Rows[0][dc].ToString()); ld.Add(dc.ColumnName, dTable.Rows[0][dc].ToString()); } foreach (string ky in ld.Keys) if (int.TryParse(ld[ky].ToString(), out QuantityInt)) ld[ky] = "integer"; else if(double.TryParse(ld[ky].ToString(), out QuantityDouble)) ld[ky]="double"; else ld[ky]="nvarchar";

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  • How to avoid translation tools from messing up HTML tags?

    - by janoChen
    I always use Google translate and paste back the the results in Vim. But for some reason Google translate also screws up the HTML tags around the content I want to translate. Is there a solution for this? For instance, the double quotes are translated to Chinese-cased double quotes: 'pictures_h2'=>“?????????? Strong and li tags are translated too (well I kinda expected that). P S : IS there any translator which respect HTML tags? or translation plugin for Vim?

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  • Why does casting a NaN to a long yield a valid result?

    - by brainimus
    In the sample code below I am dividing by zero which when I step through it with the debugger the (dividend / divisor) yields an Infinity or NaN (if the divisor is zero). When I cast this result to a long I get a valid result, usually something like -9223372036854775808. Why is this cast valid? Why doesn't it stop executing (throw an exception for example) rather than assign an arbitrary value? double divisor = 0; double dividend = 7; long result = (long)(dividend / divisor);

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  • troubles with integration on matlab

    - by user648666
    I'd like some help please I really need to solve this problem. Well before anything thank you for your time... My problem: I have a matrix (826x826 double) and I want to integrate this matrix with respect to a vector of (826x1 double) I don't have the functions of any of this. Is there a command or an algorithm to take the integral of a matrix with respect to a vector? Please I really need help, I'm such a newbie at matlab. Sincerely. George

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  • measuring uncertainty in matlabs svmclassify

    - by Mark
    I'm doing contextual object recognition and I need a prior for my observations. e.g. this space was labeled "dog", what's the probability that it was labeled correctly? Do you know if matlabs svmclassify has an argument to return this level of certainty with it's classification? If not, matlabs svm has the following structures in it: SVM = SupportVectors: [11x124 single] Alpha: [11x1 double] Bias: 0.0915 KernelFunction: @linear_kernel KernelFunctionArgs: {} GroupNames: {11x1 cell} SupportVectorIndices: [11x1 double] ScaleData: [1x1 struct] FigureHandles: [] Can you think of any ways to compute a good measure of uncertainty from these? (Which support vector to use?) Papers/articles explaining uncertainty in SVMs welcome. More in depth explanations of matlabs SVM are also welcome. If you can't do it this way, can you think of any other libraries with SVMs that have this measure of uncertainty?

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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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