October 2011 - Boost - lists.boost.org

[msm] state machine construction / destruction
by Jinsong Huang 21 Oct '11

21 Oct '11

MSM enthusiasts, I have done a performance profiling with a simple parser with 3 implementations, plain C++, SMC and Boost MSM. I was happy to learn that the MSM implementation was very efficient. I'm having some questions about MSM space allocation, please let me know if my understanding of things are wrong (very likely). I work in a high performance computing environment so I will try to minimize unnecessary object constructions. Is it possible for the data in the state machine backend live somewhere else external to the state machine? If that's possible then I can put the state machine's internal states close to the data that needs to be manipulated and the state machine itself is data-less and I can have a single copy of the state machine and each data item carries everything. I know this breaks encapsulation but I'm just wondering. The state machine has a events queue (std::deque?), can I choose to not have this and other data structures I don't think I will need? Thanks, -jh

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enable_if : how to make it work in the case of templated method of a template base inherited several times
by nico 21 Oct '11

21 Oct '11

I hope the subject didn't make you run away ;-) Let me be clearer (I'll try at least): If I have a template base class with a template method : template <typename T> class S { public: template <typename U> void f(U p, typename enable_if<is_same<T, U> >::type*dummy = 0) { std::cout << p << std::endl; } }; For the example, I simplify the method : it must "exists" only if T == U If A is this class: class A : public S<int> {}; Then I have what I want: int i = 1; A a; a.f(i); compiles, but double d = 2.0; a.f(d); doesn't compile : error: no matching function for call to ‘A::f(double&)’ It is the expected behavior. Now let's A inherit from S<double> also : class A : public S<int>, public S<double> {}; Then the following code doesn't compile : int i = 1; A a; a.f(i); error: request for member ‘f’ is ambiguous error: candidates are: template<class U> void S::f(U, typename boost::enable_if<boost::is_same<T, U>, void>::type*) [with U = U, T = double] error: template<class U> void S::f(U, typename boost::enable_if<boost::is_same<T, U>, void>::type*) [with U = U, T = int] I expected there is no ambiguity : f<int> exists only for S<int> In the compiler error, we can notice that T is known when this piece of code is compiled, but not U (U = U). Any explanation or "workaround" ? Thanks. Nicolas.

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[Re:Opaque Typedef] observations on opaque typedef
by Robert Ramey 20 Oct '11

20 Oct '11

Vicent - I saw your post on this subject some months ago and I've reviewed the thread. I didn't look at the code though. I also looked at the C++0x document and I have something to say about this. a) as you know I'm the author of BOOST_STRONG_TYPEDEF which lets one assign a unique type to some primitive integer type. I did this to permit overloads on integers used for different purposes. The new types created had all the properties of integer types but they were all different types. So far so good. b) I eventually found the BOOST_STRONG_TYPEDEF did too much - what I really wanted to not to inherit all the interoperations but only some of them. So I've reduced or eliminated usage of BOOST_STRONG_TYPE from the serialization library implementation. Never the less, I do see it useful in other contexts so your efforts to create and opaque typedef seem useful to me. c) BUT now I really want something else. I want the ability to assign a new type to an existing type. The current typedef has the feature that if two different names are used for the same type, a new type is NOT created. That is typedef creates a synonym rather than a new type. I thought that C++0x template alias would do this. But a careful reading of the standard document that I have leads me to believe that if two names are aliased to the same underlying type - a new type is not created - just like the current typedef. So what we have in the new C++ is basically a templated typedef. d) what I really need is the equivalent to #define OPAQUE_TYPEDEF(name, t) \ struct name : public t {}; so I can say struct dollar_amount { ... operator *(const & rhs) const {..} // don't include this operator - makes no sense }; OPAQUE_TYPEDEF(debit, dollar_amount); OPAQUE_TYPEDEF(price, dollar_amount) and then say void f(debit, t){...} void f(price t){...} Notice in my example, I don't want debit and price types to be true types and not just synonyms for dollar_amount. I realize that this is whole different kettle of fixh than BOOST_STRONG_TYPE or OPAQUE_TYPE. So this might be considered off topic. or maybe not. Comments welcome. Also anyone can feel free to correct my understanding of the template alias feature of C++0x to create new types. Robert Ramey

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missing locale/info.hpp
by markus.rauber＠bluewin.ch 20 Oct '11

20 Oct '11

Hi in your documentation you mention the availability of info.hpp (located in /boost/locale) I've just downloaded the latest 1.47 release and there's no such "locale" subdirectory and no info.hpp file containing a <locale> include statement. I'd like to use the language settings provided with this header file. Where can it be found? Where can the corresponding library be found? Thanks for your feedback Markus

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using nabble to read/write on Boost ML
by lcaminiti 20 Oct '11

20 Oct '11

Hello all, I use Nabble to read/write Boost emails but it puts special HTML instead of the template parenthesis: template<typename T> Other Nabble users (if any), is there a way to configure Nabble to not do this? If not, is there another web-based tool (a side from my personal gmail) I can use to view and reply Boost emails? Thanks a lot. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-using-nabble-to-read-write-on-Boos… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Re: [boost] [utility] How can I contribute?
by Stewart, Robert 20 Oct '11

20 Oct '11

Andrzej Krzemienski wrote: > > I am not well familiar with Boost procedures, so I apologize > if my question is silly. There's a good deal published on the web site (see Community). > I found a bug (or a missing feature) in template > boost::value_initialized. I found that a bug report and the > proposed resolution are already there in BoostTrac: > https://svn.boost.org/trac/boost/ticket/5483. Is there a way I > could help speed the process of getting it fixed up? Can people > from outside commit changes to Boost trunk? Outsiders may not commit changes. Adding "[utility]" to your subject would have helped to focus attention on the affected library. Boost.Utility has no single maintainer, so adding that to the subject will attract attention from the interested parties and your asking about the bug reported six months ago will help to increase attention. You might want to add your own details to the Trac report, including whether the proposed patch fixes your problem. (If it did, it should encourage the maintainers to accept the patch.) _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

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Re: [boost] [locale] missing locale/info.hpp
by Stewart, Robert 20 Oct '11

20 Oct '11

markus.rauber(a)bluewin.ch wrote: > > in your documentation you mention the availability of info.hpp > (located in /boost/locale) I've just downloaded the > latest 1.47 release and there's no such "locale" subdirectory > and no info.hpp file containing a <locale> include statement. > > I'd like to use the language settings provided with this > header file. > Where can it be found? > Where can the corresponding library be found? Boost.Locale was accepted into Boost this past spring (see http://www.boost.org/community/review_schedule.html for details). It has not yet been made part of a release (as can be seen from http://www.boost.org/doc/libs/, which you can access from boost.org's Libraries link.) FYI: It is also helpful to include the library name in square brackets in your subject to ensure the library author/maintainer discovers it (see http://www.boost.org/community/policy.html#subject-line) Conventionally, the library name is rendered in lower case. I have done so in my reply, so Artyom may well have more details to offer you. _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

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RFC: A better shared_array
by Olaf van der Spek 20 Oct '11

20 Oct '11

Hi, The current shared_array doesn't keep track of size. This greatly decreases it's usefulness. So I wrote a variant that does: http://pastebin.com/wkdLVqM1 Any interest in such a variant? Olaf

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How can I contribute?
by Andrzej Krzemienski 20 Oct '11

20 Oct '11

Hi, I am not well familiar with Boost procedures, so I apologize if my question is silly. I found a bug (or a missing feature) in template boost::value_initialized. I found that a bug report and the proposed resolution are already there in BoostTrac: https://svn.boost.org/trac/boost/ticket/5483. Is there a way I could help speed the process of getting it fixed up? Can people from outside commit changes to Boost trunk? Regards, &rzej

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Re: [boost] Interest in StaticVector - fixed capacity vector
by Nevin Liber 19 Oct '11

19 Oct '11

On 14 October 2011 05:32, Dave Abrahams <dave(a)boostpro.com> wrote: > Use-cases, please! I worked on a messaging system that created messages via serialization (that took iterators) and delivered them via UDP. Most messages were small (<100 bytes) with occasional messages 1K-2K in size. To give ourselves breathing room, we allowed messages up to, say, 32K, as it would be a non-trivial effort to implement splitting/reassembly of messages. > How could it ever be a "drop-in replacement for vector" For over a decade, the mental model for calling push_back, insert, resize, etc. is that it they have no preconditions to check. This is true *for every standard container* (which supports the corresponding operation, of course). You want to *silently* break that consistency. That will lead to buffer overrun bugs, which we know are hard to debug and I'm not saying we don't need the unchecked functionality. I'm saying it should never be spelled p-u-s-h-_-b-a-c-k, i-n-s-e-r-t, r-e-s-i-z-e, etc. (which is one of the reasons I'm arguing against making it policy based). I'm strongly opposed to any solution that uses the same function signatures as the standard containers that isn't as safe and easy to call as the ones in the standard containers. -- Nevin ":-)" Liber <mailto:nevin@eviloverlord.com> (847) 691-1404

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