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  • C#: Need one of my classes to trigger an event in another class to update a text box

    - by Matt
    Total n00b to C# and events although I have been programming for a while. I have a class containing a text box. This class creates an instance of a communication manager class that is receiving frames from the Serial Port. I have this all working fine. Every time a frame is received and its data extracted, I want a method to run in my class with the text box in order to append this frame data to the text box. So, without posting all of my code I have my form class... public partial class Form1 : Form { CommManager comm; public Form1() { InitializeComponent(); comm = new CommManager(); } private void updateTextBox() { //get new values and update textbox } . . . and I have my CommManager class class CommManager { //here we manage the comms, recieve the data and parse the frame } SO... essentially, when I parse that frame, I need the updateTextBox method from the form class to run. I'm guessing this is possible with events but I can't seem to get it to work. I tried adding an event handler in the form class after creating the instance of CommManager as below... comm = new CommManager(); comm.framePopulated += new EventHandler(updateTextBox); ...but I must be doing this wrong as the compiler doesn't like it... Any ideas?!

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  • Commenting out portions of code in Scala

    - by akauppi
    I am looking for a C(++) #if 0 -like way of being able to comment out whole pieces of Scala source code, for keeping around experimental or expired code for a while. I tried out a couple of alternatives and would like to hear what you use, and if you have come up with something better? // Simply block-marking N lines by '//' is one way... // <tags> """ anything My editor makes this easy, but it's not really The Thing. It gets easily mixed with actual one-line comments. Then I figured there's native XML support, so: <!-- ... did not work --> Wrapping in XML works, unless you have <tags> within the block: class none { val a= <ignore> ... cannot have //<tags> <here> (not even in end-of-line comments!) </ignore> } The same for multi-line strings seems kind of best, but there's an awful lot of boilerplate (not fashionable in Scala) to please the compiler (less if you're doing this within a class or an object): object none { val ignore= """ This seems like ... <truly> <anything goes> but three "'s of course """ } The 'right' way to do this might be: /*** /* ... works but not properly syntax highlighed in SubEthaEdit (or StackOverflow) */ ***/ ..but that matches the /* and */ only, not i.e. /*** to ***/. This means the comments within the block need to be balanced. And - the current Scala syntax highlighting mode for SubEthaEdit fails miserably on this. As a comparison, Lua has --[==[ matching ]==] and so forth. I think I'm spoilt? So - is there some useful trick I'm overseeing?

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  • Enumeration trouble: redeclared as different kind of symbol

    - by Matt
    Hello all. I am writing a program that is supposed to help me learn about enumeration data types in C++. The current trouble is that the compiler doesn't like my enum usage when trying to use the new data type as I would other data types. I am getting the error "redeclared as different kind of symbol" when compiling my trangleShape function. Take a look at the relevant code. Any insight is appreciated! Thanks! (All functions are their own .cpp files.) header file #ifndef HEADER_H_INCLUDED #define HEADER_H_INCLUDED #include <iostream> #include <iomanip> using namespace std; enum triangleType {noTriangle, scalene, isoceles, equilateral}; //prototypes void extern input(float&, float&, float&); triangleType extern triangleShape(float, float, float); /*void extern output (float, float, float);*/ void extern myLabel(const char *, const char *); #endif // HEADER_H_INCLUDED main function //8.1 main // this progam... #include "header.h" int main() { float sideLength1, sideLength2, sideLength3; char response; do //main loop { input (sideLength1, sideLength2, sideLength3); triangleShape (sideLength1, sideLength2, sideLength3); //output (sideLength1, sideLength2, sideLength3); cout << "\nAny more triangles to analyze? (y,n) "; cin >> response; } while (response == 'Y' || response == 'y'); myLabel ("8.1", "2/11/2011"); return 0; } triangleShape shape # include "header.h" triangleType triangleShape(sideLenght1, sideLength2, sideLength3) { triangleType triangle; return triangle; }

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  • Why do I get this strange output behavior?

    - by WilliamKF
    I have the following program test.cc: #include <iostream> unsigned char bogus1[] = { // Changing # of periods (0x2e) changes output after periods. 0x2e, 0x2e, 0x2e, 0x2e }; unsigned int bogus2 = 1816; // Changing this value changes output. int main() { std::clog << bogus1; } I build it with: g++ -g -c -o test.o test.cc; g++ -static-libgcc -o test test.o Using g++ version 3.4.6 I run it through valgrind and nothing is reported wrong. However the output has two extra control characters and looks like this: .... Thats a control-X and a control-G at the end. If you change the value of bogus2 you get different control characters. If you change the number of periods in the array the issue goes away or changes. I suspect it is a memory corruption bug in the compiler or iostream package. What is going on here?

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  • Getting Started: Silverlight 4 Business Application

    - by Eric J.
    With the arrival of VS 2010 and Silverlight 4, I decided it's time to look into Silverlight and understand how to build a 3-Tier business application. After several hours of searching for and reading documentation and tutorials, I'm thoroughly confused (and that doesn't happen easily). Here are some specific points I don't understand. I welcome guidance on any of them, and also would appreciate any references to a really good tutorial. Brad Abrahm's What is a .NET RIA services (written for Silverlight 3) seemed very promising, until I realized I don't have System.Web.Ria.dll on my system. Am I missing an optional download? Was this rolled into another DLL for Silverlight 4? Did this go away in favor of something else in Silverlight 4? This recent blog says to start from a Silverlight Business Application, remove unwanted stuff, create a WCF RIA services Class Library project, and copy files and references from the Business Application to the WCF RIA services project, while manually updating resource references (perhaps bug in B2 compiler). Is this really the right road to go down? It seems very clumsy. My requirements are to perform very simple CRUD on straightforward business objects. I'm looking forward to suggestions on how to do that the Silverlight 4 way.

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  • Creating an object in the loop

    - by Jacob
    std::vector<double> C(4); for(int i = 0; i < 1000;++i) for(int j = 0; j < 2000; ++j) { C[0] = 1.0; C[1] = 1.0; C[2] = 1.0; C[3] = 1.0; } is much faster than for(int i = 0; i < 1000;++i) for(int j = 0; j < 2000; ++j) { std::vector<double> C(4); C[0] = 1.0; C[1] = 1.0; C[2] = 1.0; C[3] = 1.0; } I realize this happens because std::vector is repeatedly being created and instantiated in the loop, but I was under the impression this would be optimized away. Is it completely wrong to keep variables local in a loop whenever possible? I was under the (perhaps false) impression that this would provide optimization opportunities for the compiler. EDIT: I use VC++2005 (release mode) with full optimization (/Ox)

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  • Scala path dependent return type from parameter

    - by Rich Oliver
    In the following code using 2.10.0M3 in Eclipse plugin 2.1.0 for 2.10M3. I'm using the default setting which is targeting JVM 1.5 class GeomBase[T <: DTypes] { abstract class NewObjs { def newHex(gridR: GridBase, coodI: Cood): gridR.HexRT } class GridBase { selfGrid => type HexRT = HexG with T#HexTr def uniformRect (init: NewObjs) { val hexCood = Cood(2 ,2) val hex: HexRT = init.newHex(selfGrid, hexCood)// won't compile } } } Error message: Description Resource Path Location Type type mismatch; found: GeomBase.this.GridBase#HexG with T#HexTr required: GridBase.this.HexRT (which expands to) GridBase.this.HexG with T#HexTr GeomBase.scala Why does the compiler think the method returns the type projection GridBase#HexG when it should be this specific instance of GridBase? Edit transferred to a simpler code class in responce to comments now getting a different error message. package rStrat class TestClass { abstract class NewObjs { def newHex(gridR: GridBase): gridR.HexG } class GridBase { selfGrid => def uniformRect (init: NewObjs) { val hex: HexG = init.newHex(this) //error here } class HexG { val test12 = 5 } } } . Error line 11:Description Resource Path Location Type type mismatch; found : gridR.HexG required: GridBase.this.HexG possible cause: missing arguments for method or constructor TestClass.scala /SStrat/src/rStrat line 11 Scala Problem Update I've switched to 2.10.0M4 and updated the plug-in to the M4 version on a fresh version of Eclipse and switched to JVM 1.6 (and 1.7) but the problems are unchanged.

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  • passing multidimensional arrays to function

    - by Pegah
    hi! I have a method in my class which uses a 3dimensional tfpairexp as input parameter. and I need to use the values in tfpairexp later. void calctfpairexp (int tf1, int tf2, double tfpairexp[][2][3]) { int ctr,c; for (int j = 0; j < cchips && (c = chips[j].crepls); j += c) { int ctrl_no=0; for (int *p = chips[j].ctrl ; p && (ctr=*p)>=0; ++p,ctrl_no++) { for (int k = 0; k < c; ++k) { tfpairexp[j][ctrl_no][k]=interactionFunc(2,3,1); } } } } I call the method inside the class like this: calctfpairexp(tf1,tf2,tfpairexp); and I need to use values inside tfpairexp in next lines. but the compiler gives error in this line: tfpairexp[j][ctrl_no][k]=interactionFunc(2,3,1); and says that the tfpairexp variable is not defined in the calctfpairexp function. any idea?

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  • Can't get node.js built on cygwin

    - by mwt
    Following the instructions here: https://github.com/ry/node/wiki/Building-node.js-on-Cygwin-(Windows) I've tried installing on two machines, either of which I'd be happy to get up and running. WinXP On 'make', I get: Build failed: -> task failed <err #2>: {task: libv8.a SConstruct -> libv8.a} According to the instructions, this is caused by having $SHELL set to a Windows style path, but I've set it to /bin/bash and get the same error. Win7 On './configure', I get: $ ./configure Checking for program g++ or c++ : /usr/bin/g++ Checking for program cpp : /usr/bin/cpp Checking for program ar : /usr/bin/ar Checking for program ranlib : /usr/bin/ranlib Checking for g++ : ok Checking for program gcc or cc : /usr/bin/gcc 0 [main] python 1092 C:\bin\python.exe: *** fatal error - unable to remap \\?\C:\lib\python2.6\lib-dynload\_functools.dll to same address as parent: 0x360000 != 0x3E0000 Stack trace: Frame Function Args 002891E8 6102749B (002891E8, 00000000, 00000000, 00000000) 002894D8 6102749B (61177B80, 00008000, 00000000, 61179977) 0028A508 61004AFB (611A136C, 61241CF4, 00360000, 003E0000) End of stack trace 0 [main] python 3536 fork: child 1092 - died waiting for dll loading, errno 11 /Users/Michael/Desktop/node/wscript:177: error: could not configure a c compiler! I've run 'rebaseall' and restarted the machine but still get that error. Edit: Ok, rebaseall was apparently erroring on some mingw stuff, so I edited the rebaseall script to fix that, and now it configures on Win7. The new problem is that it emits the exact same error as my XP machine now when I try to make. This is on tag v0.3.5.

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  • C++ iterator and const_iterator problem for own container class

    - by BaCh
    Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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  • C: Fifo between threads, writing and reading strings

    - by Yonatan
    Hello once more dear internet, I writing a small program that among other things, writes a log file of commands received. to do that, I want to use a thread that all it should do is just attempt to read from a pipe, while the main thread will write into that pipe whenever it should. Since i don't know the length of each string command, i thought about writing and reading the pointer to the char buf[MAX_MESSAGE_LEN]. Since what i've tried so far doesn't work, i'll post my best effort :P char str[] = "hello log thread 123456789 10 11 12 13 14 15 16 17 18 19\n"; if (pipe(pipe_fd) != 0) return -1; pthread_t log_thread; pthread_create(&log_thread,NULL, log_thread_start, argv[2]); success_write = 0; do { write(pipe_fd[1],(void*)&str,sizeof(char*)); } while (success_write < sizeof(char*)); and the thread does this: char buffer[MAX_MSGLEN]; int success_read; success_read = 0; //while(1) { do { success_read += read(pipe_fd[0],(void*)&buffer, sizeof(char*)); } while (success_read < sizeof(char*)); //} printf("%s",buffer); (Sorry if this doesn't indent, i can't seem to figure out this editor...) oh, and pipe_fd[2] is a global parameter. So, any help with this, either by the way i thought of, or another way i could read strings without knowing the length, would be much appreciated. On a side note, i'm working on Eclipse IDE C/C++, version 1.2.1 and i can't seem to set up the compiler so it will link the pthread library to my project. I've resorted to writing my own Makefile to make it (pun intended :P) work. Anyone knows what to do ? i've looked online, but all i find are solutions that are probably good on an older version because the tabs and option keys are different. Anyways, Thanks a bunch internet ! Yonatan

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  • how can access public properties of MasterPage from external Class ?

    - by eugeneK
    Why i can't access MasterPage's public property (MessagePlaceholder) from other Class (Errors) ? Error compiler gives me is "Error 1 The type or namespace name 'MyMasterPage' could not be found (are you missing a using directive or an assembly reference?)" my master page code behind using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class MyMasterPage : System.Web.UI.MasterPage { public string MessagePlaceholder { get { return messagePlaceholder.InnerHtml; } set { messagePlaceholder.InnerHtml = value; } } protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { messagePlaceholder.InnerHtml = Errors.getMessage(); } } } my Errors Class public static string getMessage() { HttpContext c = HttpContext.Current; string messageType = ""; if (c.Session["errorMessage"] != null) { messageType = "errorMessage"; } else if (c.Session["successMessage"] != null) { messageType = "successMessage"; } if (!string.IsNullOrEmpty(messageType)) { StringBuilder userMessageSb = new StringBuilder(); userMessageSb.Append(string.Format("<div id=\"{0}\" title=\"{1}\">{2}</div>", messageType, messageType.Replace("Message",string.Empty), c.Session[messageType])); // fix so message will not re-appear c.Session.Remove(messageType); messageType = userMessageSb.ToString(); } return messageType; } public static void setSuccess(string successMessage, bool isRedirect) { HttpContext.Current.Session["successMessage"] = successMessage; } public static void setError(string errorMessage, bool isRedirect) { HttpContext.Current.Session["errorMessage"] = errorMessage; if (!isRedirect) { ((HttpContext.Current.CurrentHandler as System.Web.UI.Page).Master as MyMasterPage).MessagePlaceholder = getMessage(); } } this is how i set error if (true) { Errors.setError("this is an error demo", false); return; } or with redirect after error if (true) { Errors.setError("yet another error", true); Response.Redirect("~/error.aspx"); }

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  • How to call implemented method of generic enum in Java?

    - by Justin Wiseman
    I am trying pass an enum into a method, iterate over that enums values, and call the method that that enum implements on all of those values. I am getting compiler errors on the part "value.getAlias()". It says "The method getAlias() is undefined for the type E" I have attempted to indicate that E implements the HasAlias interface, but it does not seem to work. Is this possible, and if so, how do I fix the code below to do what I want? The code below is only meant to show my process, it is not my intention to just print the names of the values in an enum, but to demonstate my problem. public interface HasAlias{ String getAlias(); }; public enum Letters implements HasAlias { A("The letter A"), B("The letter B"); private final String alias; public String getAlias(){return alias;} public Letters(String alias) { this.alias = alias; } } public enum Numbers implements HasAlias { ONE("The number one"), TWO("The number two"); private final String alias; public String getAlias(){return alias;} public Letters(String alias) { this.alias = alias; } } public class Identifier { public <E extends Enum<? extends HasAlias>> void identify(Class<E> enumClass) { for(E value : enumClass.getEnumConstants()) { System.out.println(value.getAlias()); } } }

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  • How do C++ compilers actually pass reference parameters?

    - by T.E.D.
    This question came about as a result of some mixed-langauge programming. I had a Fortran routine I wanted to call from C++ code. Fortran passes all its parameters by reference (unless you tell it otherwise). So I thought I'd be clever (bad start right there) in my C++ code and define the Fortran routine something like this: extern "C" void FORTRAN_ROUTINE (unsigned & flag); This code worked for a while but (of course right when I needed to leave) suddenly started blowing up on a return call. Clear indication of a munged call stack. Another engineer came behind me and fixed the problem, declaring that the routine had to be deinfed in C++ as extern "C" void FORTRAN_ROUTINE (unsigned * flag); I'd accept that except for two things. One is that it seems rather counter-intuitive for the compiler to not pass reference parameters by reference, and I can find no documentation anywhere that says that. The other is that he changed a whole raft of other code in there at the same time, so it theoretically could have been another change that fixed whatever the issue was. So the question is, how does C++ actually pass reference parameters? Is it perhaps free to do copy-in, copy-out for small values or something? In other words, are reference parameters utterly useless in mixed-language programming? I'd like to know so I don't make this same code-killing mistake ever again.

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  • c++ floating point precision loss: 3015/0.00025298219406977296

    - by SigTerm
    The problem. Microsoft Visual C++ 2005 compiler, 32bit windows xp sp3, amd 64 x2 cpu. Code: double a = 3015.0; double b = 0.00025298219406977296; //*((unsigned __int64*)(&a)) == 0x40a78e0000000000 //*((unsigned __int64*)(&b)) == 0x3f30945640000000 double f = a/b;//3015/0.00025298219406977296; the result of calculation (i.e. "f") is 11917835.000000000 (*((unsigned __int64*)(&f)) == 0x4166bb4160000000) although it should be 11917834.814763514 (i.e. *((unsigned __int64*)(&f)) == 0x4166bb415a128aef). I.e. fractional part is lost. Unfortunately, I need fractional part to be correct. Questions: 1) Why does this happen? 2) How can I fix the problem? Additional info: 0) The result is taken directly from "watch" window (it wasn't printed, and I didn't forget to set printing precision). I also provided hex dump of floating point variable, so I'm absolutely sure about calculation result. 1) The disassembly of f = a/b is: fld qword ptr [a] fdiv qword ptr [b] fstp qword ptr [f] 2) f = 3015/0.00025298219406977296; yields correct result (f == 11917834.814763514 , *((unsigned __int64*)(&f)) == 0x4166bb415a128aef ), but it looks like in this case result is simply calculated during compile-time: fld qword ptr [__real@4166bb415a128aef (828EA0h)] fstp qword ptr [f] So, how can I fix this problem? P.S. I've found a temporary workaround (i need only fractional part of division, so I simply use f = fmod(a/b)/b at the moment), but I still would like to know how to fix this problem properly - double precision is supposed to be 16 decimal digits, so such calculation isn't supposed to cause problems.

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  • C++ ambiguous template instantiation

    - by aaa
    the following gives me ambiguous template instantiation with nvcc (combination of EDG front-end and g++). Is it really ambiguous, or is compiler wrong? I also post workaround à la boost::enable_if template<typename T> struct disable_if_serial { typedef void type; }; template<> struct disable_if_serial<serial_tag> { }; template<int M, int N, typename T> __device__ //static typename disable_if_serial<T>::type void add_evaluate_polynomial1(double *R, const double (&C)[M][N], double x, const T &thread) { // ... } template<size_t M, size_t N> __device__ static void add_evaluate_polynomial1(double *R, const double (&C)[M][N], double x, const serial_tag&) { for (size_t i = 0; i < M; ++i) add_evaluate_polynomial1(R, C, x, i); } // ambiguous template instantiation here. add_evaluate_polynomial1(R, C, x, serial_tag());

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  • Why do I have to specify pure virtual functions in the declaration of a derived class in Visual C++?

    - by neuviemeporte
    Given the base class A and the derived class B: class A { public: virtual void f() = 0; }; class B : public A { public: void g(); }; void B::g() { cout << "Yay!"; } void B::f() { cout << "Argh!"; } I get errors saying that f() is not declared in B while trying do define void B::f(). Do I have to declare f() explicitly in B? I think that if the interface changes I shouldn't have to correct the declarations in every single class deriving from it. Is there no way for B to get all the virtual functions' declarations from A automatically? EDIT: I found an article that says the inheritance of pure virtual functions is dependent on the compiler: http://www.objectmentor.com/resources/articles/abcpvf.pdf I'm using VC++2008, wonder if there's an option for this.

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  • Questions regarding detouring by modifying the virtual table

    - by Elliott Darfink
    I've been practicing detours using the same approach as Microsoft Detours (replace the first five bytes with a jmp and an address). More recently I've been reading about detouring by modifying the virtual table. I would appreciate if someone could shed some light on the subject by mentioning a few pros and cons with this method compared to the one previously mentioned! I'd also like to ask about patched vtables and objects on the stack. Consider the following situation: // Class definition struct Foo { virtual void Call(void) { std::cout << "FooCall\n"; } }; // If it's GCC, 'this' is passed as the first parameter void MyCall(Foo * object) { std::cout << "MyCall\n"; } // In some function Foo * foo = new Foo; // Allocated on the heap Foo foo2; // Created on the stack // Arguments: void ** vtable, uint offset, void * replacement PatchVTable(*reinterpret_cast<void***>(foo), 0, MyCall); // Call the methods foo->Call(); // Outputs: 'MyCall' foo2.Call(); // Outputs: 'FooCall' In this case foo->Call() would end up calling MyCall(Foo * object) whilst foo2.Call() call the original function (i.e Foo::Call(void) method). This is because the compiler will try to decide any virtual calls during compile time if possible (correct me if I'm wrong). Does that mean it does not matter if you patch the virtual table or not, as long as you use objects on the stack (not heap allocated)?

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  • Can knowing C actually hurt the code you write in higher level languages?

    - by Jurily
    The question seems settled, beaten to death even. Smart people have said smart things on the subject. To be a really good programmer, you need to know C. Or do you? I was enlightened twice this week. The first one made me realize that my assumptions don't go further than my knowledge behind them, and given the complexity of software running on my machine, that's almost non-existent. But what really drove it home was this Slashdot comment: The end result is that I notice the many naive ways in which traditional C "bare metal" programmers assume that higher level languages are implemented. They make bad "optimization" decisions in projects they influence, because they have no idea how a compiler works or how different a good runtime system may be from the naive macro-assembler model they understand. Then it hit me: C is just one more abstraction, like all others. Even the CPU itself is only an abstraction! I've just never seen it break, because I don't have the tools to measure it. I'm confused. Has my mind been mutilated beyond recovery, like Dijkstra said about BASIC? Am I living in a constant state of premature optimization? Is there hope for me, now that I realized I know nothing about anything? Is there anything to know, even? And why is it so fascinating, that everything I've written in the last five years might have been fundamentally wrong? To sum it up: is there any value in knowing more than the API docs tell me? EDIT: Made CW. Of course this also means now you must post examples of the interpreter/runtime optimizing better than we do :)

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  • Strange Access Denied warning when running the simplest C++ program.

    - by DaveJohnston
    I am just starting to learn C++ (coming from a Java background) and I have come across something that I can't explain. I am working through the C++ Primer book and doing the exercises. Every time I get to a new exercise I create a new .cpp file and set it up with the main method (and any includes I think I will need) e.g.: #include <list> #include <vector> int main(int argc, char **args) { } and just to make sure I go to the command prompt and compile and run: g++ whatever.cpp a.exe Normally this works just fine and I start working on the exercise, but I just did it and got a strange error. It compiles fine, but when I run it it says Access Denied and AVG pops up telling me that a threat has been detected 'Trojan Horse Generic 17.CKZT'. I tried compiling again using the Microsoft Compiler (cl.exe) and it runs fines. So I went back, and added: #include <iostream> compiled using g++ and ran. This time it worked fine. So can anyone tell me why AVG would report an empty main method as a trojan horse but if the iostream header is included it doesn't?

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  • Pointers and Addresses in C

    - by Mohit
    #include "stdio.h" main() { int i=3,*x; float j=1.5,*y; char k='c',*z; x=&i; y=&j; z=&k; printf("\nAddress of x= %u",x); printf("\nAddress of y= %u",y); printf("\nAddress of z= %u",z); x++; y++;y++;y++;y++; z++; printf("\nNew Address of x= %u",x); printf("\nNew Address of y= %u",y); printf("\nNew Address of z= %u",z); printf("\nNew Value of i= %d",i); printf("\nNew Value of j= %f",j); printf("\nNew Value of k= %c\n",k); } Output: Address of x= 3219901868 Address of y= 3219901860 Address of z= 3219901875 New Address of x= 3219901872 New Address of y= 3219901876 New Address of z= 3219901876 New Value of i= 3 New Value of j= 1.500000 New Value of k= c The new address of variable y and z are same. How can two variables have same address and et have different values? Note: I used gcc compiler on Ubuntu 9.04

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  • Why is it that an int in C++ that isnt initialized (then used) doesn't return an error?

    - by omizzle
    I am new to C++ (just starting). I come from a Java background and I was trying out the following piece of code that would sum the numbers between 1 and 10 (inclusive) and then print out the sum: /* * File: main.cpp * Author: omarestrella * * Created on June 7, 2010, 8:02 PM */ #include <cstdlib> #include <iostream> using namespace std; int main() { int sum; for(int x = 1; x <= 10; x++) { sum += x; } cout << "The sum is: " << sum << endl; return 0; } When I ran it it kept printing 32822 for the sum. I knew the answer was supposed to be 55 and realized that its print the max value for a short (32767) plus 55. Changing int sum; to int sum = 0; would work (as it should, since the variable needs to be initialized!). Why does this behavior happen, though? Why doesnt the compiler warn you about something like this? I know Java screams at you when something isnt initialized. Thank you.

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  • "Function object is unsubscriptable" in basic integer to string mapping function

    - by IanWhalen
    I'm trying to write a function to return the word string of any number less than 1000. Everytime I run my code at the interactive prompt it appears to work without issue but when I try to import wordify and run it with a test number higher than 20 it fails as "TypeError: 'function' object is unsubscriptable". Based on the error message, it seems the issue is when it tries to index numString (for example trying to extract the number 4 out of the test case of n = 24) and the compiler thinks numString is a function instead of a string. since the first line of the function is me defining numString as a string of the variable n, I'm not really sure why that is. Any help in getting around this error, or even just help in explaining why I'm seeing it, would be awesome. def wordify(n): # Convert n to a string to parse out ones, tens and hundreds later. numString = str(n) # N less than 20 is hard-coded. if n < 21: return numToWordMap(n) # N between 21 and 99 parses ones and tens then concatenates. elif n < 100: onesNum = numString[-1] ones = numToWordMap(int(onesNum)) tensNum = numString[-2] tens = numToWordMap(int(tensNum)*10) return tens+ones else: # TODO pass def numToWordMap(num): mapping = { 0:"", 1:"one", 2:"two", 3:"three", 4:"four", 5:"five", 6:"six", 7:"seven", 8:"eight", 9:"nine", 10:"ten", 11:"eleven", 12:"twelve", 13:"thirteen", 14:"fourteen", 15:"fifteen", 16:"sixteen", 17:"seventeen", 18:"eighteen", 19:"nineteen", 20:"twenty", 30:"thirty", 40:"fourty", 50:"fifty", 60:"sixty", 70:"seventy", 80:"eighty", 90:"ninety", 100:"onehundred", 200:"twohundred", 300:"threehundred", 400:"fourhundred", 500:"fivehundred", 600:"sixhundred", 700:"sevenhundred", 800:"eighthundred", 900:"ninehundred", } return mapping[num] if __name__ == '__main__': pass

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  • Using static variables for Strings

    - by Vivart
    below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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  • Segmentation Fault when trying to push a string to the back of a list.

    - by user308012
    I am trying to write a logger class for my C++ calculator, but I'm experiencing a problem while trying to push a string into a list. I have tried researching this issue and have found some information on this, but nothing that seems to help with my problem. I am using a rather basic C++ compiler, with little debugging utilities and I've not used C++ in quite some time (even then it was only a small amount). My code: #ifndef _LOGGER_H_ #define _LOGGER_H_ #include <iostream> #include <list> #include <string> using std::cout; using std::cin; using std::endl; using std::list; using std::string; class Logger { private: list<string> *mEntries; public: Logger() { // Initialize the entries list mEntries = new list<string>(); } ~Logger() { // Release the list mEntries->clear(); delete mEntries; } // Public Methods void WriteEntry(string entry) { // *** BELOW LINE IS MARKED WITH THE ERROR *** mEntries->push_back(string(entryData)); } void DisplayEntries() { cout << endl << "**********************" << endl << "* Logger Entries *" << endl << "**********************" << endl << endl; for(list<string>::iterator it = mEntries->begin(); it != mEntries->end(); it++) { cout << *it << endl; } } }; #endif I am calling the WriteEntry method by simply passing in a string, like so: mLogger->WriteEntry("Testing"); Any advice on this would be greatly appreciated.

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