c++ programmers' salaries

Hello, I'm Alberto from Italy, and I would be glad to know if it's true that a good C++ programmer is very well payed in the U.S.A. and in Australia. Thanks, Alberto.

Why Insulation is a Good Investment

Why Insulation is a Good Investment Investing in products to make homes more energy efficient pays significant dividends over a lifetime =97 with none of the wild fluctuations of Wall Street. Insulation contributes to: - Greater comfort - Even temperature distribution - Improved acoustics - Better moisture control, which can reduce floor squeaks, drywall cracks, structure damage and condensation - Potential for increased resale value: Installing proper insulation levels can also make your home more attractive to potential buyers. In fact, most buyers list energy-efficiency as a

optimizing the integer rescaling

Hello, I am trying to optimize integer rescaling (see example at the end). There is a range or integer elements (in the example, elements are of type unsigned short), current range maximum, and the desired maximum. Straight forward way is to multiply by new maximum, and then to divide by old maximum (taking care about the overflow). Are there better ways of rescaling the integers? /////////////////////////////////// #include <iostream> unsigned short a = 0x1234; // value in the range to rescale unsigned short b = 0x3fff; // new maximum range value unsigned short c

Why is it printing ABC

string func() { string msg="ABC"; return msg; } int main() { string s; s=func(); cout<<s; return 0; } The program prints s as "ABC", but msg was a local string of func() and not of main & hence the output should have been any garbage value but not the same string as "ABC". Is it occuring because on the top of the stack(that gets generated on function call), the value of msg remains and it is assigned to variable s?? But then, if I want to verify that, how can I call another function in between the call to func() and assignment of the returned value to s?? or if th

Get TYPE* array from vector<TYPE> - is this OK?

Hi all! Given: std::vector<TYPE> v; void process(size_t count, TYPE* data); Is there any problem if I do if (!v.empty()) { std::vector<TYPE>::reference r = *v.begin(); // or r = v[0]; // or r = v.at(0); process_raw(v.size(), &p); } ? (This is what I do all the time to interface with lower-level code, but I've always been wondering if there's some issue in doing things like these). TIA, Goran.

what does ## operator does in C ?

I just want to know the function of ## operator.

Calling const-members

Hi again! I am still learning through examples, and still I am struggling with matrix classes! :) I have a probably naive question: how do I "force" C++ to use a const member? I mean, I have learned (through your suggestions) about const members, for example my at() member in the matrix class: class matrix { public: matrix(unsigned int rows, unsigned int cols); matrix(matrix const& src); virtual ~matrix(); virtual double& at(unsigned int r, unsigned int c); virtual double at(unsigned int r, unsigned int c) const; // ... } Now, when I print

How to access elements of a range in a vector??

Hi, I want to do a task of modifying the elements in a range, say 5th element to 10th element.. I also know that there is a function TRANSFORM which is used to transform the elements of any container, say a vector, but in that function, the arguments are iterators, and what I have is a range and not iterators to these elements. Eg vector<int> v; v.transform(v.begin(),v.end(),v.begin(),modifying_func); //this, I want to apply not from begin to end, but from say, element at index i to index j; //similarly, if I want to know the values in a range of vector or list, not from begin to

Range-based for loop and ADL

Range-based for loop description says 6.5.4/1: "... begin-expr and end-expr are begin(__range) and end(__range), respectively, where begin and end are looked up with argument-dependent lookup (3.4.2)." And 3.4.2 says at 3.4.2/3: "Let X be the lookup set produced by unqualified lookup (3.4.1) and let Y be the lookup set produced by argument dependent lookup (defined as follows). If X contains - a declaration of a class member, or - a block-scope function declaration that is not a using-declaration, or - a declaration that is neither a function or a function template then

Boost function and bind issue

This code compiles: boost::asio::ip::tcp::acceptor m_acceptor; // declared in a class connector::pointer new_conn(new connector(m_acceptor.io_service())); m_acceptor.async_accept ( new_conn->socket(), boost::bind ( &timingserver::handle_accept, this, boost::asio::placeholders::error, new_conn ) ); So now I want to pull out the boost::bind part and make a function object of it. boost::function < void ( const boost::system::error_code &, boost::asio::ip::tcp

What's the "%02X" specifier doing?

Hi, ----------code---- int main(){ char Md5Str[34] = "670B14728AD9902AECBA32E22FA4F6BDx"; char Md5Value[1]; sscanf(Md5Str, "%02X", &Md5Value[0]); } -------------------- It gives me "run-time check failure #2 stack around the variable was corrupted" error. But I expected the Md5Value array is large enough to hold the only value I interested in. I searched the Internet and someone says that sscanf will append a '\0' character in the end, so Md5Value size should be at least two. But I still got error until Md5Value size is as large as 4. Also no error suggested for the follo

historical data from many sources: design questions

Hello, I have measurements done daily (work days) for the past 20 years or so, in the order then of 5000 or so entries. I currently have them in a text file (I've hand written the parser but I'll move to boost::spirit eventually) The application is growing: .. I may move to 20 years worth of measures every few seconds and arrive at a range of 50 000 000 entries. Each entry is probably 64 bytes. .. I may use a database .. I may receive the data over a network socket I have a class 'historical_data' that currently holds the 5000 in memory. A standalone function (in the same

Are additional constructors for standard containers allowed?

With MSVC 10.0 std::bitset<32>( 666u ) does not compile. Apparently due to an extra constructor taking 'int' argument. Is that allowed by the standard? Cheers, - Alf -- blog at <url: http://alfps.wordpress.com>

"partial" iterator?

Hello, I have a std::map<std::string, boost::shared_ptr<my_type_t>>. I often lookup based on the key (std::string) I have a use case where I want to iterate over all the map except for keys that begin with "RF". I could iterate and check if iterator->first.find("RF")==0, then ignore it. typedef std::map<std::string, boost::shared_ptr<my_type_t>> my_container_t; my_container_t my_container; for (my_container_t::const_iterator i=my_container.begin(); i!=my_container.end(); ++i) if (i->first.first.find("RF")!=0) //proceed Is there a better way ? perhaps a smar

Use Cases for Concurrent Data Structures

Libraries of data structures designed to support concurrent operations and to scale well with the number of threads are common, e.g., ConcurrentHashMap and ConcurrentLinkedQueue in Java, ConcurrentQueue and ConcurrentBag in .NET, concurrent_queue and concurrent_vector in TBB and PPL. If the comments in a recent thread in comp.lang.c++ ( http://tinyurl.com/2ey8mta ) are representative, however, there is considerable skepticism that such data structures are useful and some concern that designs employing them are almost certainly misguided. Considerable googling on my part has fai

Using "setlocate()" to get the language

Hello, I'm writing some cross-platform software in C++, within it I have a list of strings for various languages - My problem now is, how do I determine the language setting of the person running the code so I can present them information in the correct language? I'd rather not have to resort to an entire framework just for this small function. I tried "setlocale()" which always returns "C" on my Debian Lenny test machine. I don't mind having slightly different functions for each OS (I believe there are functions in the Windows API to determine language, so that's taken care of)

operator++ execution order differs between scalar types and classes

Hi, Can anyone explain please why gcc (and possibly other compilers too) treats scalar types and classes differently in terms of the order in which their operator++ is executed? For example, the following code: int x(0), y(0); y = x++ + x++; printf("x=%d y=%d\n", x, y); yields output: x=2 y=0 as if the code had been: int x(0), y(0); y = x + x; x++; x++; printf("x=%d y=%d\n", x, y); On the other hand, if I replace 'int' with a class that has all relevant ctors and operators (including operator++) defined: MyIntClass x(0), y(0); y = x++ + x++; printf("x=%d y

does map find guarantee to not copy mapped value?

Hello, I find myself writing a lot of code like the one below where I find something out of a map and then use a reference to second to interrogate the mapped object: #include <iostream> #include <map> class Expensive { /* lots of stuff here... */ }; int main() { std::map<int,Expensive> m; m.insert(std::make_pair(1,Expensive(3))); // and then later std::map<int,Expensive>::const_iterator it = m.find(1); const Expensive& expensive = (*it).second; // use expensive here - is this safe? } Is this practice safe? I've just determined on VC9 compiler that the

complexity of trigonometric functions

Hello, I have a piece of code that I am trying to optimize. It is nothing special - just some calculations, including trigonometric functions (bunch of multiplications with sin and cos here and there). My code duplicates in some places, but that is ok. The questions are : How complex are sin and cos functions? Are they simple look up tables? Or are they some super-complex calculations. If translated to multiplication/addition, how many multiplications/additions would one sin or cos involve? I am well aware this is implementation dependant, but it is probably done in very

How to initialise member variable in template construction

I am trying to set the strategy (algorithm) used in a context by template. Here is my context class (which is incorrectly implemented): template <class TStrategy> class Context //TStrategy is the algorithm { private: TStrategy * strategy_; //knows about StrategyInterface public: void execute() const { strategy_->execute(); } }; The strategies: class StrategyInterface { public: virtual void execute() const = 0; //abstract class - interface only }; //the actual concrete algorithms class ConcreteStrategy

Variables in "for" Loop

Hi, Why does for (list<string> newlines = frame(oldlines), list<string>::iterator line = newlines.begin(); line != newlines.end(); ++line) not work, while list<string> newlines = frame(oldlines); for (list<string>::iterator line = newlines.begin(); line != newlines.end(); ++line) does? Regards.

Design Problem 2

Hi. I have another design problem. I hope someone can help me. Thanks in advance. I want to write a "library" consisting in a bunch of objects like Info, Utils, etc.. I made a member with each of these inside de main class (the "library") and made the constructors private for Info, Utils, etc. and made them friend classes of the main class. Is this the right approach or should I use heritance from a base class? I also need to access some of the methods in Utils from Info, for instance, Format date function, trims, etc. etc. meaning that utils will be accessible from outside th

std vector iterator optimization question

hi, there, ---------code 1------------- for (vector<int>::interator it = somevector.begin(); it != somevector.end(); it++){...} ---------code 2------------- vector<int>::iterator stop = somevector.end(); for (vector<int>::interator it = somevector.begin(); it != stop; it++) {...} Question: If the somevector's length does not change, is code2 a better implementation than code1 (since it saves the end() call for each loop)? For const_iterator, does stl already do the optimization so that code1 and code2 won't have much difference? Thanks a lot. zl2k

simple question about typedefs....

extern DNSServiceCreateConnection(DNSServiceRef *sdRef); typedef struct _DNSServiceRef_t *DNSServiceRef; This statement creates a type called DNSServiceRef, which is a pointer to a structure??? But I have no idea what a _DNSServiceRef_t is... DNSServiceRef r; // Is just an uninitialized pointer? Am I correct in assuming that there is NO such structure as a _DNSServiceRef_t or that it is meant to be 'opaque' to me? I'm asking because I'm trying to port this c/c++ code into another language and I need to be sure I understand the data types being passed.... _DNSServiceRef

How to tell if an exception has currently been thrown and is being processed ?

Hello What is the function that could tell if there is an exception currently being thrown, that is causing stack unwinding ? I guess it was a function returning true during unwinding and false otherwise. Also, is there a way to get the current exception object (other then as the argument to the catch handler) ? Is there a way to store or keep the exception object (and its type) for later processing outside of the handler or the try-catch function that caught it ? Thank you, Timothy Madden