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  • Implementing Operator Overloading with Logarithms in C++

    - by Jacob Relkin
    Hello my friends, I'm having some issues with implementing a logarithm class with operator overloading in C++. My first goal is how I would implement the changeBase method, I've been having a tough time wrapping my head around it. My secoond goal is to be able to perform an operation where the left operand is a double and the right operand is a logarithm object. Here's a snippet of my log class: // coefficient: double // base: unsigned int // number: double class _log { double coefficient, number; unsigned int base; public: _log() { base = rand(); coefficient = rand(); number = rand(); } _log operator+ ( const double b ) const; _log operator* ( const double b ) const; _log operator- ( const double b ) const; _log operator/ ( const double b ) const; _log operator<< ( const _log &b ); double getValue() const; bool changeBase( unsigned int base ); }; You guys are awesome, thank you for your time.

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  • What are the alternatives to public fields?

    - by James
    I am programming a game in java, and as the question title suggestions i am using public fields in my classes. (for the time being) From what i have seen public fields are bad and i have some understanding why. (but if someone could clarify why you should not use them, that would be appreciated) The thing is that also from what i have seen, (and it seems logical) is that using private fields, but using getters and setters to access them is also not good as it defeats the point of using private fields in the first place. So, my question is, what are the alternatives? or do i really have to use private fields with getters and setters? For reference here is one of my classes, and some of its methods. I will elaborate more if needs be. //The player's fields. public double health; public String name; public double goldCount; public double maxWeight; public double currentWeight; public double maxBackPckSlts; public double usedBackPckSlts; // The current back pack slots in use public double maxHealth; // Maximum amount of health public ArrayList<String> backPack = new ArrayList<String>(); //This method happens when ever the player dynamically takes damage(i.e. when it is not scripted for the player to take damage. //Parameters will be added to make it dynamic so the player can take any spread of damage. public void beDamaged(double damage) { this.health -= damage; if (this.health < 0) { this.health = 0; } } public void gainHealth(double gainedHp) { this.health += gainedHp; if (this.health > this.maxHealth) { this.health = this.maxHealth; } }

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  • Using OpenGL vertex buffers in C++.

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

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  • C struct written in file, open with Java

    - by DaunnC
    For example in C I have structure: typedef struct { int number; double x1; double y1; double x2; double y2; double x3; double y3; } CTRstruct;` Then I write it to file fwrite(&tr, 1, sizeof(tr), fp); (tr - its CTRstruct var, fp - File pointer); Then I need to read it with Java! I really don't know how to read struct from file... I tried to read it with ObjectInputStream(), last idea is to read with RandomAccessFile() but I also don't know how to... (readLong(), readDouble() also doesn't work, it works ofcource but doesn't read correct data). So, any idea how to read C struct from binary file with Java? If it's interesting, my version to read integer (but it's ugly, & I don't know what to do with double): public class MyDataInputStream extends DataInputStream{ public MyDataInputStream(InputStream AIs) { super(AIs); } public int readInt1() throws IOException{ int ch1 = in.read(); int ch2 = in.read(); int ch3 = in.read(); int ch4 = in.read(); if ((ch1 | ch2 | ch3 | ch4) < 0) throw new EOFException(); return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0)); } with double we can deal the same way (like with int or with long (8bytes) & then convert to double with native func).

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  • C#: An object reference is required for the non-static field, method, or Property

    - by Omin
    I feel bad for asking this when there are so many questions that are related but I was not able to find/understand the answer I am looking for. // 2. Develop a program to convert currency X to currency Y and visa versa. using System; class Problem2 { static void Main (string[] args) { while (true) { Console.WriteLine ("1. Currency Conversion from CAD to Won"); Console.WriteLine ("2. Currency Conversion from Won to Cad"); Console.Write ("Choose from the Following: (1 or 2)? "); int option = int.Parse( Console.ReadLine() ); //double x; if (option == 1) { Console.WriteLine ("Type in the amount you would like to Convert CAD to Won: "); //double y =double.Parse( Console.ReadLine()); //Console.WriteLine( cadToWon( y ) ); Console.WriteLine( cadToWon( double.Parse( Console.ReadLine() ) )); } if (option == 2) { Console.WriteLine ("Type in the amount you would like to Convert Won to CAD: "); Console.WriteLine( wonToCad (double.Parse( Console.ReadLine()))); } } } double cadToWon( double x ) { return x * 1113.26; } double wonToCad( double x) { return x / 1113.26; } } This give me the Error messgae "An object reference is required for the non-static field, method, or property 'Problem2..." I know that I'll be able to run the program if I add static infront of the methods but I'm wondering why I need it (I think it's because Main is static?) and what do I need to change in order to use these methods without adding static to them? Thank you

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  • [C++] Trouble declaring and recognizing global functions

    - by Sarah
    I've created some mathematical functions that will be used in main() and by member functions in multiple host classes. I was thinking it would be easiest to make these math functions global in scope, but I'm not sure how to do this. I've currently put all the functions in a file called Rdraws.cpp, with the prototypes in Rdraws.h. Even with all the #includes and externs, I'm getting a "symbol not found" error at the first function call in main(). Here's what I have: // Rdraws.cpp #include <cstdlib> using namespace std; #include <cmath> #include "Rdraws.h" #include "rng.h" extern RNG rgen // this is the PRNG used in the simulation; global scope void rmultinom( double p_trans[], int numTrials, int numTrans, int numEachTrans[] ) { // function 1 def } void rmultinom( const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]) { // function 2 def } int rbinom( int nTrials, double pLeaving ) { // function 3 def } // Rdraws.h #ifndef RDRAWS #define RDRAWS void rmultinom( double[], int, int, int[] ); void rmultinom( const double[], const int, int, int[] ); int rbinom( int, double ); #endif // main.cpp ... #include "Rdraws.h" ... extern void rmultinom(double p_trans[], int numTrials, int numTrans, int numEachTrans[]); extern void rmultinom(const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]); extern int rbinom( int n, double p ); ... int main() { ... } I'm pretty new to programming. If there's a dramatically smarter way to do this, I'd love to know.

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  • C++, inject additional data in a method

    - by justik
    I am adding the new modul in some large library. All methods here are implemented as static. Let mi briefly describe the simplified model: typedef std::vector<double> TData; double test ( const TData &arg ) { return arg ( 0 ) * sin ( arg ( 1 ) + ...;} double ( * p_test ) ( const TData> &arg) = &test; class A { public: static T f1 (TData &input) { .... //some computations B::f2 (p_test); } }; Inside f1() some computations are perfomed and a static method B::f2 is called. The f2 method is implemented by another author and represents some simulation algorithm (example here is siplified). class B { public: static double f2 (double ( * p_test ) ( const TData &arg ) ) { //difficult algorithm working p_test many times double res = p_test(arg); } }; The f2 method has a pointer to some weight function (here p_test). But in my case some additional parameters computed in f1 for test() methods are required double test ( const TData &arg, const TData &arg2, char *arg3.... ) { } How to inject these parameters into test() (and so to f2) to avoid changing the source code of the f2 methods (that is not trivial), redesign of the library and without dirty hacks :-) ? The most simple step is to override f2 static double f2 (double ( * p_test ) ( const TData &arg ), const TData &arg2, char *arg3.... ) But what to do later? Consider, that methods are static, so there will be problems with objects. Thanks for your help.

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  • Variable from block is put into a calculation but throws off wrong reading

    - by user2926620
    I am having troubles with trying to retrieve a double variable that is already established outside the block and called inside but I want to return the value of the same variable so that I can apply it to a calculation. the variable that I want returned is: double quarter = 0; but when I plug it into quarter in my first else/if statement, it plugs in 0 and not the value in my switch block. What can I do to retrieve the value? double quarter = 0; //Date entry will be calculated by how much KW user enters switch (input) { case "2/15/13": quarter = kwUsed * 0.10; break; case "4/15/13": quarter = kwUsed * 0.12; break; case "8/15/13": quarter = kwUsed * 0.15; break; case "11/15/13": quarter = kwUsed * 0.15; break; default: System.out.println("Invalid date"); } //Declaring variables for calculations double base = 0; double over = 0; double excess = 0; double math1 = 0; double math2 = 0; //KW Calculations if (kwUsed <= 350) { base = quarter; }else if (kwUsed <= 500) { math1 = ((kwUsed - 350) * quarter); base = ((kwUsed * quarter) - math1); over = ((math1 * 0.1) + math1); }else if (kwUsed > 500) { math2 = ((kwUsed - 350) * 0.1); base = ((kwUsed * 0.1) - math2); math2 = ((kwUsed -350) - 50); over = ((math2 * 0.1) + (15 * 0.1)); double math3 =((kwUsed - 500) * 0.1); excess = ((math3 * 0.25) + math3); } Edited to clarify question.

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  • Unit Conversion from feet to meters

    - by user1742419
    I have to write a program that reads in a length in feet and inches and outputs the equivalent length in meters and centimeters. I have to create three functions: one for input, one or more for calculating, and one for output; And include a loop that lets the user repeat this computation for new input values until the user says he or she wants to end the program. I can't seem to get the input from one function to be used in the conversion function and then outputted by the next function. How do I do that? Thank you. #include <iostream> #include <conio.h> using namespace std; double leng; void length(double leng); double conv(double leng); void output(double leng); int main() { length(leng); conv(leng); output(leng); _getche(); return 0; } void length(double leng) { cout<<"Enter a length in feet, then enter a length in inches if needed: "; cin>>leng; return; } double conv(double leng) { return leng = leng * .3048; } void output(double leng) { cout<<"Your input is converted to "<<leng; return; }

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  • What is an efficient way to erase substrings?

    - by Legend
    I have a long string and a set of <end-index, string> list like the following: long_sentence = "This is a long long long long sentence" indices = [[6, "is"], [8, "is a"], [18, "long"], [23, "long"]] An element 6, "is" indicates that 6 is the end index of the word "is" in the string. I want to get the following string in the end: >> print long_sentence This .... long ......... long sentence" I tried an approach like this: temp = long_sentence for i in indices: temp = temp[:int(i[0]) - len(i[1])] + '.'*(len(i[1])+1) + temp[i[0]+1:] While this seems to be working, it is taking exceptionally long time (more than 6 hours on 5000 strings inside a 300 MB file). Is there a way to speed this up?

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  • .NET 3.5SP1 64-bit memory model vs. 32-bit memory model

    - by James Dunne
    As I understand it, the .NET memory model on a 32-bit machine guarantees 32-bit word writes and reads to be atomic operations but does not provide this guarantee on 64-bit words. I have written a quick tool to demonstrate this effect on a Windows XP 32-bit OS and am getting results consistent with that memory model description. However, I have taken this same tool's executable and run it on a Windows 7 Enterprise 64-bit OS and am getting wildly different results. Both the machines are identical specs just with different OSes installed. I would have expected that the .NET memory model would guarantee writes and reads to BOTH 32-bit and 64-bit words to be atomic on a 64-bit OS. I find results completely contrary to BOTH assumptions. 32-bit reads and writes are not demonstrated to be atomic on this OS. Can someone explain to me why this fails on a 64-bit OS? Tool code: using System; using System.Threading; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { var th = new Thread(new ThreadStart(RunThread)); var th2 = new Thread(new ThreadStart(RunThread)); int lastRecordedInt = 0; long lastRecordedLong = 0L; th.Start(); th2.Start(); while (!done) { int newIntValue = intValue; long newLongValue = longValue; if (lastRecordedInt > newIntValue) Console.WriteLine("BING(int)! {0} > {1}, {2}", lastRecordedInt, newIntValue, (lastRecordedInt - newIntValue)); if (lastRecordedLong > newLongValue) Console.WriteLine("BING(long)! {0} > {1}, {2}", lastRecordedLong, newLongValue, (lastRecordedLong - newLongValue)); lastRecordedInt = newIntValue; lastRecordedLong = newLongValue; } th.Join(); th2.Join(); Console.WriteLine("{0} =? {2}, {1} =? {3}", intValue, longValue, Int32.MaxValue / 2, (long)Int32.MaxValue + (Int32.MaxValue / 2)); } private static long longValue = Int32.MaxValue; private static int intValue; private static bool done = false; static void RunThread() { for (int i = 0; i < Int32.MaxValue / 4; ++i) { ++longValue; ++intValue; } done = true; } } } Results on Windows XP 32-bit: Windows XP 32-bit Intel Core2 Duo P8700 @ 2.53GHz BING(long)! 2161093208 > 2161092246, 962 BING(long)! 2162448397 > 2161273312, 1175085 BING(long)! 2270110050 > 2270109040, 1010 BING(long)! 2270115061 > 2270110059, 5002 BING(long)! 2558052223 > 2557528157, 524066 BING(long)! 2571660540 > 2571659563, 977 BING(long)! 2646433569 > 2646432557, 1012 BING(long)! 2660841714 > 2660840732, 982 BING(long)! 2661795522 > 2660841715, 953807 BING(long)! 2712855281 > 2712854239, 1042 BING(long)! 2737627472 > 2735210929, 2416543 1025780885 =? 1073741823, 3168207035 =? 3221225470 Notice how BING(int) is never written and demonstrates that 32-bit reads/writes are atomic on this 32-bit OS. Results on Windows 7 Enterprise 64-bit: Windows 7 Enterprise 64-bit Intel Core2 Duo P8700 @ 2.53GHz BING(long)! 2208482159 > 2208121217, 360942 BING(int)! 280292777 > 279704627, 588150 BING(int)! 308158865 > 308131694, 27171 BING(long)! 2549116628 > 2548884894, 231734 BING(int)! 534815527 > 534708027, 107500 BING(int)! 545113548 > 544270063, 843485 BING(long)! 2710030799 > 2709941968, 88831 BING(int)! 668662394 > 667539649, 1122745 1006355562 =? 1073741823, 3154727581 =? 3221225470 Notice that BING(long) AND BING(int) are both displayed! Why are the 32-bit operations failing, let alone the 64-bit ones?

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  • How can I adjust the CommandTImeout in DbFit for long running queries?

    - by Ben Farmer
    Is there any way to increase the CommandTimeout for DbFit queries? I have a long running stored procedure that times out when running it in a DbFit Test. It's possible for the procedure to run for a really long time (processing millions of records) and would like to have DbFit wait until it's completed, even if it takes several minutes. We are using the latest version of FitSharp (downloaded it yesterday) and use the version of DbFit that is included with FitSharp.

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  • What happens if you kill a long-running alter query?

    - by B T
    What happens if you kill a long-running alter query? Will the alter query simply revert? How long could that take (as a proportion of the time it has already been running)? What if that query is being replicated onto another server? Will killing the process on the other server revert the original server's alter query? We're running mysql

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  • Double Buffering for Game objects, what's a nice clean generic C++ way?

    - by Gary
    This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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  • Conversion from string to type 'Double' is not valid.

    - by Adnan Badar
    Hi, I am getting the following error while running a select statement (using OleDbCommand). My query is SELECT CME FROM Personnel WHERE CME = '11349D' If objOleDbCom.ExecuteScalar() 0 Then When i execute the above statement i got this error Conversion from string "11349D" to type 'Double' is not valid. My field CME data type is Text My database is Access 2007 I tried by running my query directly inside database and it is running fine. Please suggest. Thanks.

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  • How to encrypt/decrypt a long string in PHP?

    - by jodeci
    I doubt if this is encryption but I can't find a better phrase. I need to pass a long query string like this: http://test.com/test.php?key=[some_very_loooooooooooooooooooooooong_query_string] The query string contains NO sensitive information so I'm not really concerned about security in this case. It's just...well, too long and ugly. Is there a library function that can let me encode/encrypt/compress the query string into something similar to the result of a md5() (similar as in, always a 32 character string), but decode/decrypt/decompress-able?

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