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  • Convert c++ argument to int

    - by happyCoding25
    Hello, I have a small c++ program that needs to get and argument and convert it to an int. Here is my code so far: #include <iostream> using namespace std; int main(int argc,int argvx[]) { int i=1; int answer = 23; int temp; // decode arguments if(argc < 2) { printf("You must provide at least one argument\n"); exit(0); } // Convert it to an int here }

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  • NSCoding and ostream

    - by Stephen Furlani
    Is there a better way to serialize an ObjC object than using /NSKeyedArchive? I need to distribute the object through a C++ std:ostream-like object to put on another computer. The object has over 122 members of various types... for which wants me to [coder encodeObject: (id) forKey: @"blah"]; for all of them... Does anyone have a nice Perl Script that will at least write it out? I don't even know if the objects it contains implement which means this could turn into a huge ugly mess since I can't change the source of the object - I'll have to inherit & add the @interface to it... Or am I being dumb? Apple's guide doesn't help me since archiving to XML won't pass nicely though the ostream. Is there a better way to do this? -S!

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  • C++ WIN32: Short multitasking example

    - by Con Current
    I searched for examples on how to create a simple multithreaded app that does something similar to this: #include <iostream> using namespace std; int myConcurrentFunction( ) { while( 1 ) { cout << "b" << endl; } } int main( ) { // Start a new thread for myConcurrentFunction while( 1 ) { cout << "a" << endl; } } How can I get the above to output a and b "randomly" by starting a new thread instead of just calling myConcurrentFunction normally? I mean: What is the minimal code for it? Is it really only one function I have to call? What files do I need to include? I use MSVC 2010, Win32

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  • What is a good standard for code width?

    - by BillyONeal
    Hello everyone :) I've heard in several places that it's bad to have code that is too wide onscreen. For example: for (std::vector<EnumServiceInformation>::const_iterator currentService = services.begin(); currentService != services.end(); currentService++) However, I've heard many arguments for 80 character wide limits. I'm assuming this 80 character limit comes from the traditional command prompt, which is typically 80 characters wide. However -- most of us are working on something much better than a typical command prompt, and I feel that using an 80 character limit encourages use of variable names that are far too short and do not describe what the variable is used for. What is a reasonable limit for a new project with no existing coding width standard?

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  • struct with template variables in c++

    - by monkeyking
    I'm playing around with template, so I'm not trying to reinvent the std::vector, I'm trying to get a grasp of templateting in c++. Can I do the following template <typename T> typedef struct{ size_t x; T *ary; }array; What I'm trying to do is a basic templated version of typedef struct{ size_t x; int *ary; }iArray; It looks like its working if I use a class instead of struct, so is it not possible with typedef structs? thanks

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  • C++ offset of member variables?

    - by anon
    I have: class Foo { int a; int b; std::string s; char d; }; Now, I want to know the offset of a, b, s, d given a Foo* I.e. suppose I have: Foo *foo = new Foo(); (char*) foo->b == (char*) foo + ?? ; // what expression should I put in ?

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  • Floating point innacuracies

    - by Greg
    While writing a function which will perform some operation with each number in a range I ran into some problems with floating point inaccuracies. The problem can be seen in the code below: #include <iostream> using namespace std; int main() { double start = .99999, end = 1.00001, inc = .000001; int steps = (end - start) / inc; for(int i = 0; i <= steps; ++i) { cout << (start + (inc * i)) << endl; } } The problem is that the numbers the above program outputs look like this: 0.99999 0.999991 0.999992 0.999993 0.999994 0.999995 0.999996 0.999997 0.999998 0.999999 1 1 1 1 1 1.00001 1.00001 1.00001 1.00001 1.00001 1.00001 They only appear to be correct up to the first 1. What is the proper way to solve this problem?

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  • How to test if a string has a certain unicode char?

    - by Ruben Trancoso
    Supose you have a command line executable that receives arguments. This executalbe is widechar ready and you want to test if one of this arguments starts with an HYPHEN case in which its an option: command -o foo how you could test it inside your code if you don't know the charset been used by the host? Should be not possible to a given console to produce the same HYPHEN representation by another char in the widechar forest? (in such case it would be a wild char :P) int _tmain(int argc, _TCHAR* argv[]) { std::wstring inputFile(argv[1]); if(inputFile->c_str() <is an HYPHEN>) { _tprintf(_T("First argument cannot be an option")); } }

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  • SQL Server float datatype

    - by Martin Smith
    The documentation for SQL Server Float says Approximate-number data types for use with floating point numeric data. Floating point data is approximate; therefore, not all values in the data type range can be represented exactly. Which is what I expected it to say. If that is the case though why does the following return 'Yes' in SQL Server DECLARE @D float DECLARE @E float set @D = 0.1 set @E = 0.5 IF ((@D + @D + @D + @D +@D) = @E) BEGIN PRINT 'YES' END ELSE BEGIN PRINT 'NO' END but the equivalent C++ program returns "No"? #include <iostream> using namespace std; int main() { float d = 0.1F; float e = 0.5F; if((d+d+d+d+d) == e) { cout << "Yes"; } else { cout << "No"; } }

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  • Assigning unsigned char* buffer to a string

    - by CPPChase
    This question might be asked before but I couldn't find exactly what I need. My problem is, I have a buffer loaded by data downloaded from a webservice. The buffer is in unsigned char* form in which there is no '\0' at the end. Then I have a poco xml parser needs a string. I tried assigning it to string but now I realized it would cause problem such as leaking. here is the code: DOMParser::DOMParser(unsigned char* consatData, int consatDataSize, unsigned char* lagData, int lagDataSize) { Poco::XML::DOMParser parser; std::string consat; consat.assign((const char*) consatData, consatDataSize); pDoc = parser.parseString(consat); ParseConsat(); } Poco xml parser does have a ParseMemory which need a const char* and size of data but for some reason it just gives me segmentation fault. So I think it's safer to turn it to string. Thanks in advance.

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  • How can I output the fitted values?

    - by zenbomb
    Sorry if this is a novice question, but I don't understand it. I am fitting a sigmoid curve to my data with glm(). This works, I can plot the output and I see a nice sigmoid curve. However, how do I get R to return the final values it has fit? As I understand it, R fits the data to logit(y) = b0 + b1x, but when I do > summary(glm.out) I only get Call: glm(formula = e$V2 ~ e$V1, family = binomial(logit), data = e) Deviance Residuals: 1 2 3 4 5 6 7 -0.00001 -0.06612 -0.15118 -0.34237 0.20874 0.08724 -0.19557 Coefficients: Estimate Std. Error z value Pr(>|z|) (Intercept) -24.784 20.509 -1.208 0.227 e$V1 2.073 1.725 1.202 0.229 (Dispersion parameter for binomial family taken to be 1) Null deviance: 4.60338 on 6 degrees of freedom Residual deviance: 0.23388 on 5 degrees of freedom AIC: 5.8525 Number of Fisher Scoring iterations: 8 How do I get b0 and b1?

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  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

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  • Storing objects in STL vector - minimal set of methods

    - by osgx
    Hello What is "minimal framework" (necessary methods) of object, which I will store in STL <vector>? For my assumptions: #include <vector> #include <cstring> using namespace std; class Doit { private: char *a; public: Doit(){a=(char*)malloc(10);} ~Doit(){free(a);} }; int main(){ vector<Doit> v(10); } gives *** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0804b008 *** Aborted and in valgrind: malloc/free: 2 allocs, 12 frees, 50 bytes allocated.

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  • What is a cross-platform way to get the current directory?

    - by rubenvb
    I need a cross-platform way to get the current working directory (yes, getcwd does what I want). I thought this might do the trick: #ifdef _WIN32 #include <direct.h> #define getcwd _getcwd // stupid MSFT "deprecation" warning #elif #include <unistd.h> #endif #include <string> #include <iostream> using namespace std; int main() { string s_cwd(getcwd(NULL,0)); cout << "CWD is: " << s_cwd << endl; } I got this reading: _getcwd at MSDN getcwd at Kernel.org getcwd at Apple.com There should be no memory leaks, and is should work on a Mac as well, correct?

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  • Comparing structs in C++

    - by kamziro
    So in C++ There's a lot of times where you need to make an "index" class. For example: class GameID{ public: string name; int regionid; int gameid; bool operator<(const GameID& rhs) const; } Now, if we were to represent GameID as pair , the operator comparison just comes with it. Is there any other way to get that automatic operator comparison without having to use std::pair< ?

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  • which is time consuming construct in following program?

    - by user388338
    while submitting a solution for practise problem 6(odd) i got TLE error but while using using print and scanf in place cin and cout my sol was submitted successfully with 0.77s time..i want to know how can i make it more efficient link to problem is codechef problem 6 #include<iostream> #include<cstdio> using namespace std; int main() {int n,N; scanf("%d",&n); for(int l=0;l<n;l++) { scanf("%d",&N); int i=0,x; if(N<=0) continue; for(;N>=(x=(2<<i));i++); printf("%d",x/2); cout<<"\n"; } }

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  • Correct Exceptions in C++

    - by Dr.Ackula
    I am just learning how to handle errors in my C++ code. I wrote this example that looks for a text file called some file, and if its not found will throw an exception. #include <iostream> #include <fstream> using namespace std; int main() { int array[90]; try { ifstream file; file.open("somefile.txt"); if(!file.good()) throw 56; } catch(int e) { cout<<"Error number "<<e<<endl; } return 0; } Now I have two questions. First I would like to know if I am using Exceptions correctly. Second, (assuming the first is true) what is the benefit to using them vs an If else statement?

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  • C++ typedef for partial templates

    - by Gokul
    Hi, i need to do a typedef like this. template< class A, class B, class C > class X { }; template< class B, class C > typedef X< std::vector<B>, B, C > Y; I just found that it is not supported in C++. Can someone advise me on how to achieve the same through alternative means? Thanks, Gokul.

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  • Preparing for the next C++ standard

    - by Neil Butterworth
    The spate of questions regarding BOOST_FOREACH prompts me to ask users of the Boost library what (if anything) they are doing to prepare their code for portability to the proposed new C++ standard (aka C++0x). For example, do you write code like this if you use shared_ptr: #ifdef CPPOX #include <memory> #else #include "boost/shared_ptr.hpp" #endif There is also the namespace issue - in the future, shared_ptr will be part of the std, namespace - how do you deal with that? I'm interested in these questions because I've decided to bite the bullet and start learning boost seriously, and I'd like to use best practices in my code. Not exactly a flood of answers - does this mean it's a non-issue? Anyway, thanks to those that replied; I'm accepting jalfs answer because I like being advised to do nothing!

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  • Why do I get the error "X is not a member of Y" even though X is a friend of Y?

    - by user1232138
    I am trying to write a binary tree. Why does the following code report error C2039, "'<<' : is not a member of 'btree<T'" even though the << operator has been declared as a friend function in the btree class? #include<iostream> using namespace std; template<class T> class btree { public: friend ostream& operator<<(ostream &,T); }; template<class T> ostream& btree<T>::operator<<(ostream &o,T s) { o<<s.i<<'\t'<<s.n; return o; }

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  • simple c++ file opening issue

    - by Robert
    #include <iostream> #include <fstream> using namespace std; int main () { ofstream testfile; testfile.open ("test.txt"); testfile << "success!\n"; testfile.close(); return 0; } 1)called "g++ testfile.cpp" 2)created "test.txt" 3)called "chmod u+x a.out" 4)??? 5)file remains blank. I feel like an idiot for failing at something as trivial as this is supposed to be.

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  • Why is this loop over mysql resultset slow? (1.4ms per cycle)

    - by pawpro
    The $res contains around 488k rows the whole loop takes 61s! that's over 1.25ms per cycle! What is taking all that time? while($row = $res->fetch_assoc()) { $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['std'] = $row['cost_std']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['ecn'] = $row['cost_ecn']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['wnd'] = $row['cost_wnd']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['other_destination'] = $row['destination_id']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['carrier_destination'] = $row['carrier_destination_id']; } Now resultset of 10 rows, smaller arrays and performance 30 times higher (0.041ms) not the fastest still but better. while($row = $res->fetch_assoc()) { $customer[$row['id']]['name'] = $row['name']; $customer[$row['id']]['code'] = $row['customer']; }

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  • using arrays to get best memory alignment and cache use, is it necessary?

    - by Alberto Toglia
    I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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  • embedded dev. question - how to break free from a faulty serial port opening?

    - by user347266
    Under WindowsCE, C++ project, I'm trying to work with devices connected via both "real" serial ports and/or serial-to-usb wrappers ("virtual" serial ports); my problem is - when I try to open the port, if something goes wrong, the function never returns and the system goes into some non-responsive state and has to be eventually rebooted. I need to open the ports from the main thread. The question is - how can I make it happen in a controlled way?? this is the opening code snippet: std::ostringstream device_name; device_name << "\\.\COM" << port; m_port = ::CreateFile(device_name.str().c_str(), GENERIC_READ | GENERIC_WRITE, 0, // exclusive access NULL, // no security OPEN_EXISTING, FILE_FLAG_OVERLAPPED, // overlapped I/O NULL); // null template any suggestions would be greatly appreciated thanks!

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