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Re: (Spirit) Semantic Actions with member functions?
by Slava Akhmechet 12 May '03

12 May '03

I was able to get boost::bind working to bind the semantic action to the member function of MyGrammar. This seems like a superior solution. In any case, I am not sure how to pass custom data to a functor. When specifing a semantic action I have to pass the type of the functor, which implies that spirit creates a temporary object. Am I missing something? > Its time to switch your global function "myaction" into a functor. > Functors are classes that have a function call operator with the same > synopsis as your function. > The advantage is that one can pass custom data to it via a non-default > constructor. > > Functors should be and sometimes must be stateless, so care must be > employeed to use references in member data. > > Slava Akhmechet wrote: > > > I am playing around with Spirit and I seem to run into an architecture > > problem with semantic actions. Here's a small example. > > > > class MyGrammar : public grammar<MyGrammar> > > { > > public: > > template <typename ScannerT> > > struct definition > > { > > definition(MyGrammar const& self) > > { > > TestRule = str_p("test")[&my_action]; > > } > > > > rule<ScannerT> const& > > start() const { return TestRulet; }; > > > > private: > > rule<ScannerT> TestRule; > > }; > > }; > > > > My major problem is related to the fact that I cannot pass any custom > > data to my_action function. Since my_action is a global function, it > > has no knowledge of MyGrammar and must rely on global variables. > > Ideally, I would pass self to my_action to be able to hold state. What > > is a general way to get around this problem? The documention mentions > > a way to specify member functions as semantic action actors using > > boost's bind facilities but I was unable to get it to work. > > Thanks in advance. > > > > P.S. Sorry for a fairly newbie question, I was unable to find the > > answer online or in the docs. > > P.P.S. I might have accidently double posted this. Sorry about that. > > > > > > > > *Yahoo! Groups Sponsor* > > > > <http://rd.yahoo.com/M=247865.3269369.4566997.1261774/D=egroupweb/S=17050067…> > > > > > > > > Info: <http://www.boost.org> > > Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> > > Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> [mailto:boost-users-unsubscribe@yahoogroups.com>] > > > > > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service > > <http://docs.yahoo.com/info/terms/>. > > > > > Info: <http://www.boost.org> > Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> > Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> [mailto:boost-users-unsubscribe@yahoogroups.com>] > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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RE: [Boost-Users] Re: Why isn't the "last access time" part of the filesystem library?
by Ben Hutchings 11 May '03

11 May '03

Beman Dawes wrote: > At 06:13 AM 5/8/2003, Peter Dimov wrote: <snip> > >This is a misunderstanding. Last access time (struct > >stat::st_atime) and creation time (st_ctime) aren't universal. Unix's ctime is actually change time, not creation time - it is the time when certain metadata were last changed. > >Modification time (st_mtime) is common, except on read-only > >filesystems, which typically only have ctime. > > > >Judging by your "last altered" remark, you mean mtime but call > >it "last access." > > > >I think that it would be entirely reasonable (and very useful - > >can avoid reading a file if it hasn't changed since last read) > >to provide mtime. On read-only filesystems, the creation time > >should be returned. You're mixing the concepts of filesystem API and the filesystem on disk. Normally the same filesystem API can be used for any file- system supported by the OS, and file times on an inherently read- only filesystem can appear as modification time and (if the OS supports the notion) as creation or change time. > Yes, I had a similar thought. > > What format should be used to report the mtime? I'd prefer to > keep the coupling to other Boost libraries low, so I guess that > would mean just using std::time_t. That also has the advantage > of not promising higher resolution than can actually be > delivered by most platforms. Seems reasonable to me. > What to do if the filesystem doesn't attach any time at all to > a file? Fail at compile time? Always return some date in the > past, like January 1, 1900, that is impossible as a real mdate > (since computers were not invented yet) and so can be relied > upon to indicate "no date available"? Use std::time_t(-1) to be consistent with std::time and std::mktime.

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MSVC 6.0 and BOOST_HAS_PARTIAL_STD_ALLOCATOR
by Joaquín Mª López Muñoz 10 May '03

10 May '03

Shouldn't BOOST_HAS_PARTIAL_STD_ALLOCATOR be defined for MSVC 6.0? Seems it is not. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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(Spirit) Semantic Actions with member functions?
by Slava Akhmechet 09 May '03

09 May '03

I am playing around with Spirit and I seem to run into an architecture problem with semantic actions. Here's a small example. class MyGrammar : public grammar<MyGrammar> { public: template <typename ScannerT> struct definition { definition(MyGrammar const& self) { TestRule = str_p("test")[&my_action]; } rule<ScannerT> const& start() const { return TestRulet; }; private: rule<ScannerT> TestRule; }; }; My major problem is related to the fact that I cannot pass any custom data to my_action function. Since my_action is a global function, it has no knowledge of MyGrammar and must rely on global variables. Ideally, I would pass self to my_action to be able to hold state. What is a general way to get around this problem? The documention mentions a way to specify member functions as semantic action actors using boost's bind facilities but I was unable to get it to work. Thanks in advance. P.S. Sorry for a fairly newbie question, I was unable to find the answer online or in the docs. P.P.S. I might have accidently double posted this. Sorry about that.

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Help using Boost Graph Library with C++Builder 6
by asterixthegaul2003 09 May '03

09 May '03

Hi, Has anyone successfully used to Boost Graph Library (BGL) with C++Builder 6? I'm getting compilation errors. Here's what I've done: I downloaded the latest Boost (1.30.0) from boost.org and installed it. I then tried to compile the quick-tour.cpp file using the mingw compiler - no problem. I then tried to compile using the C++Builder IDE and I get the following compile errors: [C++ Error] tuple_basic.hpp(158): E2238 Multiple declaration for 'element<N,T>' [C++ Error] tuple_basic.hpp(143): E2344 Earlier declaration of 'element<N,T>' I also tried using the command line compiler (bcc32.exe - version 5.6), but get the same errors (and more). Can someone tell me what I'm doing wrong? Do I need to do something special to prepare the boost libraries for use with Borland (e.g., using the Boost Jam stuff)? Some of the documentation said I should only have to set the include path. This seemed to work with mingw. Thanks, Craig

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RE: [Boost-Users] Re: Why isn't the "last access time" part of the filesystem library?
by Ben Hutchings 09 May '03

09 May '03

richard_fanta <richard.fanta(a)morganstanley.com>: > --- In Boost-Users(a)yahoogroups.com, "Ben Hutchings" > <ben.hutchings@b...> wrote: > > richard_fanta <richard.fanta@m...> wrote: > > > Beman Dawes <bdawes@a...> wrote: > > > > At 01:02 AM 5/6/2003, richard_fanta wrote: > > > > >Looking at the filesystem library and the attributes work in > > > > >boost-sandbox, I don't immediately see "last access time" > > > > >being available for a file or directory. > > > > > > > > > >"Last access time" was included in Dietmar Kuehl's original > > > > >dir_it. > > > > > > > > > >Can someone kindly tell me why this was removed? It's highly > > > > >useful, and part of every filesystem that I've seen. <snip> > > > > Perhaps we should do more to support attribute query within the > > > > main library, but I don't really think we should include any > > > > that aren't reliably supported by at least POSIX, Windows, and > > > > ISO-9660 systems. > > > > > > Your point is well made. However, it does seem odd that a > > > feature that is useful for >95% of all typical usage shouldn't be > > > in the library. > > > > What does that figure refer to, if anything? > > Typical application usage. Yes, mileage can vary. > > Out of the last 50 apps you wrote that did file access, how many > involved CD-ROMS/DVDs that were ISO 9660 filesystems? I think most of them could quite happily have worked with files on CD-ROMs, but then I tend to write general-purpose code rather than very specific applications. A few of them needed to know file modification times. <snip> > > and updates to them may be disabled because the volume is read- > > only (whether or not the underlying medium is read-only) or > > purely to avoid the cost of updating them. > > Even if the volume is read-only from one machine, it might still > help to know when the file was last altered. > > > Note that Windows NT maintains > > access times at quite a low resolution, to reduce this cost. > > Low resolution or not, it's there. When the file changes, the > timestamp is updated. That's information that many applications > would find useful. <snip> What you're talking about is the modification time, not the access time. I agree that *that* is useful and widely supported, but it's not what you were originally asking for!

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combinations of boost::condition
by Joshua Napoli 09 May '03

09 May '03

Is there any way to wait for one of several condition objects to become ready? Is there some reason that this capability is omitted from the thread library? I would like to do something like this: mutex monitorA, monitorB; condition conditionA, conditionB; double_condition conditionAB(conditionA,conditionB); void executeNextEvent() { lock lkA(monitorA); lock lkB(monitorB); //Wait for either conditionA or conditionB to become ready. conditionAB.wait(lkA,predicateA,lkB,predicateB); if(predicateA()) { executeEventA(); } else { executeEventB(); } } [Non-text portions of this message have been removed]

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RE: [Boost-Users] Re: Why isn't the "last access time" part of the filesystem library?
by Ben Hutchings 09 May '03

09 May '03

richard_fanta <richard.fanta(a)morganstanley.com> wrote: > Beman Dawes <bdawes@a...> wrote: > > At 01:02 AM 5/6/2003, richard_fanta wrote: > > > > >Looking at the filesystem library and the attributes work in boost- > > >sandbox, I don't immediately see "last access time" being available > > >for a file or directory. > > > > > >"Last access time" was included in Dietmar Kuehl's original dir_it. > > > > > >Can someone kindly tell me why this was removed? It's highly useful, > > >and part of every filesystem that I've seen. > > > > ISO/IEC 9660:1999 filesystems don't supply a "last access" time stamp, > > perhaps because the original uses were on write-once media. > > Which filesystems adhere to this spec other than CD-ROMs? Many DVDs use this too, but for most purposes they're basically just higher-capacity CDs. > > Perhaps we should do more to support attribute query within the main > > library, but I don't really think we should include any that aren't > > reliably supported by at least POSIX, Windows, and ISO-9660 systems. > > Your point is well made. However, it does seem odd that a feature > that is useful for >95% of all typical usage shouldn't be in the > library. What does that figure refer to, if anything? > Other options: > -For ISO 9660 filesystems, use the time created as the "last > access" time stamp. > -Throw a "FeatureNotSupportedException" or somesuch. Then the feature won't be at all portable, and might as well not be supported at all. Access times are far from a universal OS feature, and updates to them may be disabled because the volume is read-only (whether or not the underlying medium is read-only) or purely to avoid the cost of updating them. Note that Windows NT maintains access times at quite a low resolution, to reduce this cost.

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RE: [Boost-Users] call_traits and MSVC 7.1
by Randy Bowen 08 May '03

08 May '03

Thanks for the info. This is illegal code. That it compiled in MSVC 7.0 was a bug. The template parameter '_Source' can not be deduced from the callsite of doSomething. 14.8.2.4 in the ISO/IEC 14882 lists the forms in which template parameters can be deduced, but a qualified name involving nested types is not one of them. I suspect it's because of something like this: [Non-text portions of this message have been removed]

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Compiling smart_ptr library
by l＠lo 08 May '03

08 May '03

Hi everybody! I'm trying to compile the smart_ptr library using the Jamfile in the test directory. Some of the test *.cpp files are compiled successfully, but some of them drops the following error: sunpro-Link-action ../../../libs/smart_ptr/test/bin/shared_ptr_alloc_ test.test/sunpro/debug/runtime-link-dynamic/shared_ptr_alloc_test Undefined first referenced symbol in file boost::__RTTI__1nFboostPchecked_deleter4nBZ___ /rest/proj/users/kercsoj/boost/boost_1_30_0/libs/s mart_ptr/test/bin/shared_ptr_alloc_test.test/sunpr o/debug/runtime-link-dynamic/ SunWS_cache/CC_obj__/_iANwWXwaw2nbnjBybyL.o [Hint: static member boost::__RTTI__1nFboostPchecked_deleter4nBZ___ must be defined in the program] It's seems, it is a common error, because it appears several times in the error output of the compiler. Has anybody any ideea, why this error message comes, and how could be corrected? Thanks, lalo

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