C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Throwing a simple exception          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message JKop Guest Posted: Sat Oct 23, 2004 6:27 pm    Post subject: Throwing a simple exception Let's say you've a very simple function, that, if it fails, should throw an exception. The thing is though, it's not important enough to go and actually define an "exception class" for, so... is there any general exception class defined in the Standard Library that I could use in such circumstances, maybe something like: namespace std { class exception {}; } void MyFunc() { //Something bad happens throw std::exception(); } -JKop Back to top John Harrison Guest Posted: Sat Oct 23, 2004 6:45 pm    Post subject: Re: Throwing a simple exception "JKop" <NULL (AT) NULL (DOT) NULL> wrote Quote: Let's say you've a very simple function, that, if it fails, should throw an exception. The thing is though, it's not important enough to go and actually define an "exception class" for, so... is there any general exception class defined in the Standard Library that I could use in such circumstances, maybe something like: namespace std { class exception {}; } void MyFunc() { //Something bad happens throw std::exception(); } std::exception is just such a class, its defined in the header <exception>. You could also consider std::runtime_error in <stdexcept>, it derives from std::exception and allows you to specify a message. throw std::runtime_error("wobbly wibble"); john Back to top Ron Natalie Guest Posted: Sat Oct 23, 2004 7:03 pm    Post subject: Re: Throwing a simple exception JKop wrote: Quote: Let's say you've a very simple function, that, if it fails, should throw an exception. The thing is though, it's not important enough to go and actually define an "exception class" for, so... is there any general exception class defined in the Standard Library that I could use in such circumstances, maybe something like: <exception> defines std::exception <stdexecpt> defines a few general purpose exceptions derived from it. Back to top David Lindauer Guest Posted: Sat Oct 23, 2004 9:20 pm    Post subject: Re: Throwing a simple exception JKop wrote: Quote: Let's say you've a very simple function, that, if it fails, should throw an exception. The thing is though, it's not important enough to go and actually define an "exception class" for, so... is there any general exception class defined in the Standard Library that I could use in such circumstances, maybe something like: namespace std { class exception {}; } void MyFunc() { //Something bad happens throw std::exception(); } -JKop for example: #include <stdexcept> using namespace std ; void myfunc(bool bad_things_happen) { if (bad_things_happen) throw runtime_error("my message here") ; // use a runtime_error since you can't associate a //message with the standard 'exception' class } int main(int argc, char **argv) { try { myfunc(true) ; } catch (runtime_error &aa) { // note you could catch 'exception' here if you want to catch all the // exceptions in stdexcept cout << aa.what() ; // prints your message } } Back to top Computer Whizz Guest Posted: Sun Oct 24, 2004 10:07 am    Post subject: Re: Throwing a simple exception "David Lindauer" <camille (AT) bluegrass (DOT) net> wrote Quote: JKop wrote: Let's say you've a very simple function, that, if it fails, should throw an exception. The thing is though, it's not important enough to go and actually define an "exception class" for, so... is there any general exception class defined in the Standard Library that I could use in such circumstances, maybe something like: for example: #include <stdexcept using namespace std ; void myfunc(bool bad_things_happen) { if (bad_things_happen) throw runtime_error("my message here") ; // use a runtime_error since you can't associate a //message with the standard 'exception' class } int main(int argc, char **argv) { try { myfunc(true) ; } catch (runtime_error &aa) { // note you could catch 'exception' here if you want to catch all the // exceptions in stdexcept cout << aa.what() ; // prints your message } } Wow - I knew about the exception messages - but didn't know you could catch them... Can you catch -- ========= Comp Whizz ========= (The C++ beginner) Back to top David Lindauer Guest Posted: Sun Oct 24, 2004 9:11 pm    Post subject: Re: Throwing a simple exception Computer Whizz wrote: Quote: "David Lindauer" <camille (AT) bluegrass (DOT) net> wrote in message news:417ACB1B.F20CCAA9 (AT) bluegrass (DOT) net... snip Wow - I knew about the exception messages - but didn't know you could catch them... Can you catch <exception> errors too? Or is this just for <stdexcept> ? you can catch them if you want.... you can really catch anything you want. catch () is type-based and doesn't really care about specific declarations made in some header. I think I may have even caught an 'int' in some forgotten program . David Back to top Computer Whizz Guest Posted: Wed Oct 27, 2004 12:27 pm    Post subject: Re: Throwing a simple exception "David Lindauer" <camille (AT) bluegrass (DOT) net> wrote Quote: Computer Whizz wrote: "David Lindauer" <camille (AT) bluegrass (DOT) net> wrote in message news:417ACB1B.F20CCAA9 (AT) bluegrass (DOT) net... snip Wow - I knew about the exception messages - but didn't know you could catch them... Can you catch <exception> errors too? Or is this just for <stdexcept> ? you can catch them if you want.... you can really catch anything you want. catch () is type-based and doesn't really care about specific declarations made in some header. I think I may have even caught an 'int' in some forgotten program . David Along these lines - I just read in accel C++ that errors have different types. Say you wanted an outer catch that would catch different types of errors for multiple reasons - I don't know exactly why - maybe just to save me typing loads of catches around area's that would give out errors... Is there such a way to do a catch? As it seems like you can only catch the errors with the appropriate type. -- ========= Comp Whizz ========= (The C++ beginner) Back to top JKop Guest Posted: Wed Oct 27, 2004 12:34 pm    Post subject: Re: Throwing a simple exception Quote: Say you wanted an outer catch that would catch different types of errors for multiple reasons - I don't know exactly why - maybe just to save me typing loads of catches around area's that would give out errors... Is there such a way to do a catch? As it seems like you can only catch the errors with the appropriate type. What the hell is an "outer catch"? Anyway: catch(...) { } If you wanted a bullet-proof program: int main() { try { //Program goes here } catch(...) { return 1; } } But still, you've to watch out for global objects whose contructor may throw... -JKop Back to top Richard Herring Guest Posted: Wed Oct 27, 2004 1:09 pm    Post subject: Re: Throwing a simple exception In message <clo4ep$ss7$1 (AT) newsg1 (DOT) svr.pol.co.uk>, Computer Whizz <old486whizz (AT) hotmail (DOT) com> writes Quote: Along these lines - I just read in accel C++ that errors Exceptions. Quote: have different types. An exception is simply something that is thrown and caught. You can throw pretty much anything. Quote: Say you wanted an outer catch that would catch different types of errors for multiple reasons - I don't know exactly why - maybe just to save me typing loads of catches around area's that would give out errors... Is there such a way to do a catch? As it seems like you can only catch the errors with the appropriate type. Read about polymorphism and the "is-a" relationship. If you derive your different error types from a single type Base, you can catch them all with "catch (Base const & b)" because each derived type is-a Base. -- Richard Herring Back to top David Lindauer Guest Posted: Thu Oct 28, 2004 1:31 am    Post subject: Re: Throwing a simple exception Richard Herring wrote: Quote: In message <clo4ep$ss7$1 (AT) newsg1 (DOT) svr.pol.co.uk>, Computer Whizz [email]old486whizz (AT) hotmail (DOT) com[/email]> writes Along these lines - I just read in accel C++ that errors Exceptions. have different types. An exception is simply something that is thrown and caught. You can throw pretty much anything. Say you wanted an outer catch that would catch different types of errors for multiple reasons - I don't know exactly why - maybe just to save me typing loads of catches around area's that would give out errors... Is there such a way to do a catch? As it seems like you can only catch the errors with the appropriate type. Read about polymorphism and the "is-a" relationship. If you derive your different error types from a single type Base, you can catch them all with "catch (Base const & b)" because each derived type is-a Base. along those lines you can catch anything in <stdexcept> with catch( exception const &b) because everything in that header is derived from exception... David Back to top Computer Whizz Guest Posted: Thu Oct 28, 2004 7:36 am    Post subject: Re: Throwing a simple exception "David Lindauer" <camille (AT) bluegrass (DOT) net> wrote Quote: Richard Herring wrote: In message <clo4ep$ss7$1 (AT) newsg1 (DOT) svr.pol.co.uk>, Computer Whizz [email]old486whizz (AT) hotmail (DOT) com[/email]> writes Along these lines - I just read in accel C++ that errors Exceptions. Yes - sorry... I'm thinking back to VB and generally call any bug an "error" on my part - since it IS. Quote: have different types. An exception is simply something that is thrown and caught. You can throw pretty much anything. Say you wanted an outer catch that would catch different types of errors for multiple reasons - I don't know exactly why - maybe just to save me typing loads of catches around area's that would give out errors... Is there such a way to do a catch? As it seems like you can only catch the errors with the appropriate type. Read about polymorphism and the "is-a" relationship. If you derive your different error types from a single type Base, you can catch them all with "catch (Base const & b)" because each derived type is-a Base. along those lines you can catch anything in <stdexcept> with catch( exception const &b) because everything in that header is derived from exception... David Ah. Thank you very much. Will look into all this later on. -- ========= Comp Whizz ========= (The C++ beginner) Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.