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Question regarding boolalpha and lexical_cast for 1.30.0
by Paul Wendt 14 May '03

14 May '03

Hello, I'm trying to get lexical_cast to convert a std::string to bool; I realize that this is done with normal IOStreams by using boolalpha. Is there a way to do this with lexical_cast? I saw some old posts in the archives and they were apparently with older code bases because I was unable to get their code snippets to work properly [either that or my compiler is messed up :)]. For reference, I use Visual Studio .NET 2002. Thank you very much for any assistance in advance. --Paul

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RE: [Boost-Users] indentation vs. braces
by Ben Hutchings 14 May '03

14 May '03

Ryan Barrett <rbarrett(a)stanford.edu> wrote: <snip> > incidentally - and this is *way* off-topic - python's control flow is > defined by indentation. iirc, it works just like you'd want. > > however, i should offer the disclaimer that that's pretty much all i > know about python, other than the fact that ESR likes it: <snip> Some people would consider the ESR association a flaw, but that's going way off-topic. However, I do know about Python and would recommend pretty much all programmers to have a look at it.

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RE: [Boost-Users] find_if and calling a member function
by Tom Matelich 14 May '03

14 May '03

Define easier :) Not to be picky, but how little do you expect to have to type? 1) write your own algorithm find_if_equal, then you only need one bind (~10 lines of code separate from your call) 2) write a functor, ObjectNameCompare (less than 15 lines of code separate from your call) > -----Original Message----- > From: Russell Hind [mailto:yg-boost-users@gmane.org] > Sent: Tuesday, May 13, 2003 9:31 AM > To: boost-users(a)yahoogroups.com > Subject: [Boost-Users] find_if and calling a member function > > > I have an object that has a member get_name which returns a > string. I > have a collection of these objects and would like to find one with a > particular name. I am currently using find_if, equal and bind > > find_if(objects.begin(), objects.end(), > bind(equal_to<string>(), name, bind(&object::get_name, _1))); > > Given Lambda doesn't compile under BCB6, is there an easier way to do > this rather than having to make up 2 bind statements? > > Thanks > > Russell > > > > ------------------------ Yahoo! Groups Sponsor > ---------------------~--> > Rent DVDs Online - Over 14,500 titles. > No Late Fees & Free Shipping. > Try Netflix for FREE! > http://us.click.yahoo.com/YoVfrB/XP.FAA/uetFAA/EbFolB/TM > -------------------------------------------------------------- > -------~-> > > Info: <http://www.boost.org> > Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> > Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> > > > Your use of Yahoo! Groups is subject to > http://docs.yahoo.com/info/terms/ > > ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

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Test message from moderator
by Jim.Hyslop 13 May '03

13 May '03

My apologies for the noise, I'm trying to resolve some problems experienced by some users of this list. -- Jim Hyslop Moderator, Boost-users(a)yahoogroups.com

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Inconsistent regexp matching when using quantifiers?
by Dean 13 May '03

13 May '03

Hi all, I'm using regexp from boost-1.28 and experience the following behavior. Consider the following (somewhat artificial) regexp pattern: a{1}b As I expected, that pattern is found in "ab" but not "aab". To my suprise however, the same pattern *is* found in "aaab", "aaaaab", and any other string consisting of an odd number of "a"s followed by a "b". It is not found in strings consisting of an even number of "a"s followed by a "b". This seems odd (no pun intended). I see the same sort of behavior with quantifiers other than "{1}" and where the quantified expression matches other single characters. (Oddly enough, the behavior changes when using a quantified expression that matches multiple characters. "(ab){1}c" is found in "abc", "ababc", "abababc", and any other string containing "abc".) FWIW, I first observed the behavior when trying to find social security numbers with the following pattern: \d{3}-\d{2}-\d{4} As expected, that pattern was found in "123-12-1234" but not in "1234- 12-1234". However it *was* found in "1234567-12-1234". Is this behavior by design or is it a bug? If it's a bug, has it been fixed in a subsequent boost release? Also what is the correct behavior? Should "a{1}b" be found in "aab" (albeit starting at the second character)? FWIW, it's easy enough for me to workaround the current behavior with a pattern like this: (^|[^a])a{1}b Thanks, --Dean

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find_if and calling a member function
by Russell Hind 13 May '03

13 May '03

I have an object that has a member get_name which returns a string. I have a collection of these objects and would like to find one with a particular name. I am currently using find_if, equal and bind find_if(objects.begin(), objects.end(), bind(equal_to<string>(), name, bind(&object::get_name, _1))); Given Lambda doesn't compile under BCB6, is there an easier way to do this rather than having to make up 2 bind statements? Thanks Russell

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RE: [Boost-Users] boost::thread IDs
by Ben Hutchings 13 May '03

13 May '03

Mark Sizer wrote: > I know there was a discussion about the need for these and why > they're not in the library. I can't find it, however. > > I'm having the same problem the original poster had: I'm using > the thread ID as an identifier in a data structure (std::map in > this case). You can do that with Windows thread IDs, because they are simple integers. Unfortunately the Posix thread ID type (pthread_t) is an abstract data type and the only relation defined on it is equality (pthread_equal()). Some implementations use a type that can safely and correctly be compared with std::less, but there's no guarantee of that, so Boost can't offer such a guarantee either. > Now that I'm converting to the Boost threads library, I have to > change that. I'm not sure what to do instead. > > Any help, either a pointer to the original discussion or direct > suggestions, will be much appreciated. How about using pointers to boost::thread objects as IDs (they must of course be the instances used to start the thread, rather than instances created with the default constructor). Store each thread's own pointer in TLS (or TSS as Boost.Threads calls it). (This is tricky, though - you can't pass a thread's own ID to its initial function, as threads start to run immediately. I suppose you could use placement new, but that's a bit gross.) What's the need for thread IDs, anyway? Are you using a thread pool?

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boost::thread IDs
by Mark Sizer 13 May '03

13 May '03

I know there was a discussion about the need for these and why they're not in the library. I can't find it, however. I'm having the same problem the original poster had: I'm using the thread ID as an identifier in a data structure (std::map in this case). Now that I'm converting to the Boost threads library, I have to change that. I'm not sure what to do instead. Any help, either a pointer to the original discussion or direct suggestions, will be much appreciated. Thanks, - Mark P.S. Other than this glitch, my ObjectSpace Toolkit removal has been painless. Great libraries!

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scope of locked variables
by Peter G 12 May '03

12 May '03

hi there... what is the scope of locked variables? assuming that i declare a mutex in say a class scope.. and then lock it in some inner scope - say in a function.. what variables get locked? is it all the variables which are in the scope of the declaration (ie all the variables which are declared in the class)? or is it only the ones which are being used in that particular function (so that perhaps another thread could use the rest at "the same time")? for example: class Class1 { public: Class1::Class1(); ~Class1::Class1(); void f(int new) { boost::mutex::scoped_lock scoped_lock(mutex_outer) ; var1 = new; } void g(int new) { boos::mutex mutex_inner; boost::mutex::scoped_lock scoped_lock(mutex_inner) ; var1 = new; } private: boost::mutex mutex_outer; Class2 some_member_object; int var1; int var2; }; what gets locked when f() is called? when should i use g()? how do I go about just locking say var1 but NOT var2? if i lock the mutex in this class scope, does that mean that all the variables in some_member_object are locked as well? also, should i set up locks anytime i am using an object which might be accesses by another thread (even if I am just reading it) or is it enough to only lock variables when i am changing them? i know that's a lot of questions, but any help would be greatly appreciated. cheers peter

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[uBLAS] binary operation of vector and matrix with different type
by Zhang Le 12 May '03

12 May '03

hi, the following code generates a compile error raising from a macro in /ublas/traits.hpp: BOOST_STATIC_ASSERT ((boost::is_same<T1, T2>::value)); Because I'm trying to prod on a vector of size_t and a matrix of unsigned char. Because I want to save memory (the matrix is really huge) and I know the value in m will never exceed 255. The expression is ok to me (of course the result value is size_t). But the ASSERT prevent me from doing this. Is there a workaround that permits me doing this kind of case without sacrificing the memory efficiency? Using size_t in the matrix will use three times more memory. ublas::vector<size_t> v1(5); matrix<unsigned char> m(5,5); prod(m,v1); the same problem arises when I do prod(m,v2); here v2 is a vector<double> -- Sincerely yours, Zhang Le

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