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Spirit and CTTL
by Aaron Griffin 29 Sep '05

29 Sep '05

Ok, I didn't go to school for computer programming, so I never had experience with a "Compilers" class or anything related to lexing/parsing. But now I'm getting interested in it and have begun looking at some things. Spirit seems good, but it seems very weighty to work with. I was wondering if anyone has experiences with Spirit *and* CTTL and would be able to list for me some of the pros and cons of each. Spirit is, of course, a boost library and would be easier to find help and things of that nature, but CTTL seems to be a tad more lightweight (I'm not really sure). Thanks for any and all replies.

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BOOST_CHECK_CLOSE with integral types
by Will Bryant 29 Sep '05

29 Sep '05

Hi all, Is BOOST_CHECK_CLOSE supposed to work with integral types? I find that if I try: long var1 = 1001; BOOST_CHECK_CLOSE(var1, 2000L, 10L); under both MSVC 2005 and GCC 3.4, it'll pass, which is wrong as far as I can see - whereas: double var2 = 1001.0; BOOST_CHECK_CLOSE(var2, 2000.0, 10.0); fails as it should. Why is this? int has the same problem. Cheers, Will -- Will Bryant http://carcino.gen.nz/ will(a)core-dev.co.nz +64 21 655 443

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Using indirect_iterators for input
by Alexander Borghgraef 29 Sep '05

29 Sep '05

Hi all, I've been experimenting with indirect_iterator, which seems to be a very useful concept. However, I'm having some trouble getting it to work in the case where I want to fill a container with pointers to values, not just getting at the data. For example, this compiles but segfaults: std::vector < int * > v( 10 ); std::fill( boost::make_indirect_iterator( v.begin() ), boost::make_indirect_iterator( v.end() ), 1.0 ); Another case: std::vector< boost::shared_ptr<double> > v(10); std::vector< boost::shared_ptr<double> > w(10); // v gets filled somehow std::copy( boost::make_indirect_iterator( v.begin() ), boost::make_indirect_iterator( v.end() ), boost::make_indirect_iterator( w.begin() ) ); Why isn't this working? Also, some way to get it to work as a back_insert_iterator would be interesting, does this exist (aside from writing your own)? If not, are there any plans to incorporate it in future versions? -- Alex Borghgraef -- Alex Borghgraef

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[serialization] Non intrusive splitting of serialize
by Marco Segurini 28 Sep '05

28 Sep '05

Hi, I like to know if is it possible to split the non intrusive 'serialize' to 'load/save/BOOST_SERIALIZATION_SPLIT_...(<class name>)' thanks. Marco.

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Program options
by Paul Giaccone 28 Sep '05

28 Sep '05

In the documentation on program_options (program_options/overview.html), in the section Parsers Component it says "Sometimes it's desirable to specify value as several tokens. For example, an option "--email-recipient" may be followed by several emails, each as a separate command line token. This behaviour is supported, though it can lead to parsing ambiguities and is not enabled by default." This is just what I would like to. However, I haven't found anything in the documentation explaining how to do this. I don't think this can be done using positional options - is this correct? For example, I would like to be able to have command-line options along the lines of: -A 1 2 3 -B hello goodbye and have 1, 2, and 3 stored in a vector of integers associated with the -A flag, and "hello" and "goodbye" in a vector of strings associated with the -B flag. So how do I enable this? Paul Giaccone

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VC++ 7.1 and precompiled header
by Marco Segurini 28 Sep '05

28 Sep '05

Hi VC++ 7.1 compiler uses the stdafx.h to create a precompiled headers file. I usually put all the boost headers in stdafx.h but sometime strange compiler errors are reported. If I move some headers out of stdafx.h all works fine. I like to know if there is a list of boost headers that cannot be put in the stdafx.h TIA Marco.

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how to download a single library
by Stas Khirman 28 Sep '05

28 Sep '05

Hi, Is the way to extract one specific library ( smart_ptr in my case) from complete BOOST source tree? I need to use only smart_pointers, but undirtunately keeping a full BOOSt treen is too heavy for my CVS server. Are boost libraries heavy interrelated each with another? Regards Stas

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boost::is_complex
by Edward Grace 28 Sep '05

28 Sep '05

Dear all, Can someone add an is_complex<T>::value trait to type_traits.hpp ::boost::is_complex<T>::value trait to type_traits.hpp I have found myself having to do this frequently. It strikes me that for templated scientific codes it is a common requirement. Below is my implementation, please feel free to add it. I should probably inform the maintainer as well, John Maddock but there is no obvious way of contacting him via the boost site. namespace boost { /** * @brief Default trait for determining if a type is complex at * compile-time. * * If the supplied template parameter type is not a std::complex<> * then this struct is instantiated and the ::value enum will be 0 * at compile time. * * See also boost::is_float and associated in * boost/type_traits.hpp */ template <typename T> struct is_complex : ::boost::mpl::false_{}; /** * @brief Overloaded trait for std::complex<> to determine if a * type is complex at compile-time. * * If the supplied type is std::complex<double> or similar this * overloaded struct is instantiated and the ::value enum will be * 1 at compile-time. * * See also boost::is_float and associated in * boost/type_traits.hpp */ template <typename T> struct is_complex<std::complex<T> > : ::boost::mpl::true_{}; } -ed -- Dr. Edward Grace Photonics Group, Physics Department Blackett Laboratory Imperial College SW7 2BW t: 020 759 47719 e: ej.grace(a)imperial.ac.uk w: http://ptweb.op.ph.ic.ac.uk/~graceej

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[regex] Bug: negative lookahead does not work in 1.33.0
by Rob Willis 28 Sep '05

28 Sep '05

The following regex should match any document that IS NOT a pdf file: .*[.](?!pdf$).*$ This regex should match: Mynotes.doc It should fail on: Myinfo.pdf However, the above regex returns true on both using boost 1.33.0. But positive lookahead works fine: .*[.](?=pdf$).*$ Above regex correctly matches only documents ending in .pdf . Can anyone confirm this is a bug? Thanks, -Rob

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[iostreams] interrupted reads / writes
by Marcus Alanen 28 Sep '05

28 Sep '05

Hello, I have been toying with a framework for process management. I have opted to catch SIGCHLD in my signal handler to handle child processes. However, boost::iostreams does not seem to recognize system calls which are interrupted, and throws exceptions. Witness ./libs/iostreams/src/file_descriptor.cpp: errno = 0; std::streamsize result = BOOST_RTL(read)(pimpl_->fd_, s, n); if (errno != 0) throw detail::bad_read(); return result == 0 ? -1 : result; if ::read fails with errno == EINTR, a bad_read will result. This is unfortunate, as caught SIGCHLD signals will result in spurious errors, as the following strace shows: ... read(9, 0x95d83ac, 4096) = ? ERESTARTSYS (To be restarted) --- SIGCHLD (Child exited) @ 0 (0) --- waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 2407 sigreturn() = ? (mask now []) write(2, "terminate called after throwing "..., 48) = 48 write(2, "std::ios_base::failure", 22) = 22 write(2, "\'\n", 2) = 2 write(2, " what(): ", 11) = 11 write(2, "bad read", 8) = 8 write(2, "\n", 1) = 1 ... As I understand it, boost was going to use ::read(), but the SIGCHLD got in between, resulting in a an exception being thrown. I realize that boost::process is not up and running yet, so this might be a usage conflict of posix & boost. Can somebody please enlighten me what the usage pattern here should be? Thanks in advance, Marcus

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