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Re: Some remarks on PP docs
by Vesa Karvonen 11 Jun '04

11 Jun '04

Dave Abrahams: >I am not even trying to cover the whole PP library in this appendix, >much less the topic of PP metaprogramming in general. [...] [...] >... but, thanks for the suggestions. I don't mean to sound >ungrateful, but I'm really trying to limit this to a small-scale >practical overview of the things you need to know in order to get >started with the PP library. I see your point, but... >"Understanding the preprocessor and PP metaprogramming" is beyond the >scope of the book. ...while understanding all the consequences of the PP design is obviously not necessary for basic PP metaprogramming, I think that it is almost impossible to be able to use the PP (and the Boost.PP library) profitably (beoyond trivial use of macros like ENUM_PARAMS and REPEAT) without having a fairly good understanding of the capabilities and limitations of the PP. -Vesa Karvonen _________________________________________________________________ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail

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RE: [boost] Geometric Algebra Library
by Johannes Brunen 11 Jun '04

11 Jun '04

Hi Jaap, fine to hear that you are still working on your GA library. I'm eager to see such a library in the boost pool. So I'm very interested in the library. One point however, Paul Leopardi is still working on GluCat and I have the impression that he is also targeting boost. It would be fine if you could bundle together your efforts in oder to get the best of each GA libraries. With best regards, Johannes

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[serialization18] conflict definition of "is_abstract" with type traits library(in cvs)
by Allen Yao 11 Jun '04

11 Jun '04

The file is_abstract.hpp in serialization18 and is_abstract.hpp in type traits library (in cvs) have conflict definitions of "boost::is_abstract". May Ramey fix this. For now, I just comment out the latter in order to use serialization18. In addition, I am confused with the ".ipp" files in libs/serialization/src/ in serialization18. It is strange to write #include <libs/serialization/src/basic_binary_oprimitive.ipp> // for serialization18 in user code instead of #include <boost/serialization/basic_binary_oprimitive.ipp> // for serialization17 I wonder why these files can not be just named ".hpp" Ramey, when will we see the serialization library in boost cvs, please? Thank you:)

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[thread] Thread specific pointer cleanup handlers
by Malcolm Noyes 11 Jun '04

11 Jun '04

During my 'research' into different ways to implement thread specfic storage (tss) on Win32, I needed to implement custom cleanup handlers. The thread_dev branch allows for a custom cleanup handler on the basis of 'one cleanup handler per global object instance'. This is *not* the same as 'one cleanup handler per tss object instance' since with tss there is of course one object instance per thread. Consider: void no_cleanup(int*) { // do nothing } thread_specific_ptr p(no_cleanup); int main(int, char*[]) { int some_number = 42; // leaving aside why someone might want to do this, it's // the mechanincs that we're interested in! p.reset(&some_number); // fine p.reset(new int(0)); // leak - 'p' has no cleanup! return 0; } The theoretical alternative would be to allow (enforce?) a different cleanup handler per thread object, e.g.: void no_cleanup(int*) { // do nothing } void delete_cleanup(int* pd) { delete pd; } thread_specific_ptr p; int main(int, char*[]) { int some_number = 42; // this time call reset with a specfic handler for this thread //object instance p.reset(&some_number, no_cleanup); // fine p.reset(new int(0), delete_cleanup); // ok now, will call delete return 0; } My feeling is that boost::thread should only allow the first form and document that the use above leads to unspecified behaviour (it may not be a memory leak, we don't know what the cleanup handler may do). My only reason for this however is that allowing the latter case is probably not a frequent use and makes the implementation much complicated. Does anyone think the latter is required ? Malcolm Malcolm Noyes

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[Test] Linking
by David B. Held 11 Jun '04

11 Jun '04

What is the canonical way to link the Boost.Test library? Is it better to just include the sources in the project, or to try to link to a built library? Dave --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com) Version: 6.0.701 / Virus Database: 458 - Release Date: 6/7/2004

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boost::transform_iterator and boost::lambda functors
by Maxim Yegorushkin 10 Jun '04

10 Jun '04

Is there a way to make a boost::lambda functor adaptable, that is to make it define result_type? There is a ret<> function template that lets one specify the result type, but the returned functor still does not have result_type typedef. I've encountered the problem trying to use boost::transform_iterator with a boost::lambda functor: std::vector<int> intVect; boost::make_transform_iterator(intVect.begin(), boost::lambda::_1 / 2); transform_iterator<> does not compile comlaining the functor does not have result_type. As a workaround I had to write something like: template<class R, class T> struct result_type_wrapper : T { typedef R result_type; result_type_wrapper(T const& t) : T(t) {} }; template<class R, class T> inline result_type_wrapper<R, T> result_type(T const& t) { return t; } boost::make_transform_iterator(intVect.begin(), result_type<int>(boost::lambda::_1 / 2)); Am I missing something? Is there a way to avoid using result_type_wrapper<>? -- Maxim Yegorushkin

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Re: Some remarks on PP docs
by Vesa Karvonen 10 Jun '04

10 Jun '04

David B. Held: >It's hard enough getting one's head around the PP lib without having to >be an expert in it already. [...] >It's a shame, because there's a lot of code that would benefit from the >PP lib that almost certainly isn't because of the difficult learning >curve. Learning Boost.Preprocessor is like learning a rather verbose and intricate programming language. It is not really surprising that it can be difficult to learn, although the documentation, at least the parts that I wrote, could certainly be improved. It is possible to implement a language using the C99 (or even the less capable C++97) preprocessor that would be much less verbose and intricate and would be significantly easier to use (see http://groups.yahoo.com/group/boost/files/Order/ for details), but it would come at some cost in efficiency (on some compilers the cost would probably be prohibitive and on some compilers the cost is insignificant). -Vesa Karvonen _________________________________________________________________ Protect your PC - get McAfee.com VirusScan Online http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

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Re: Some remarks on PP docs
by Vesa Karvonen 10 Jun '04

10 Jun '04

>techniques.html: Since I initially wrote the document, I might as well comment. >I was really confused by the use of the word "standard". This would >be clearer: > > It is usually okay to reuse a single generic macro name like > BOOST_PP_DEF throughout your code because the macro is both defined > and undefined very close to its point of use. Yeah, there is probably a better way to convey the idea. >Although I don't know why you'd want to advocate that over using a >descriptive name. Because those macros are essentially [used like] lambda expressions: ad hoc, short, local functions that you usually do not even want to name. There is also an additional benefit of using a single generic name. If you forget to write the #undef, you will more likely get a warning (or an error) from the preprocessor. #undefining local macros helps to avoid macro replacement related problems. >A clearer divider between examples would be a *huge* help visually. >An <hr> would be enough, for example. Looking at an old revision in CVS, this used to be the case. >?? Where is BOOST_PP_EMPTY used in this example? I think I know what >you mean, but really, you need to show it! Looking at old revisions in CVS, it used to be there (use of BOOST_PP_EMPTY). > Note: BOOST_PP_EMPTY with the () never gets expanded. > >This sounds self-contradictory. Just above you said it expands (to >nothing)! Again, looking old revisions in CVS, it used to read "without". > The () is necessary to invoke a function-like macro. > >No duh; I think stating the obvious that way only adds confusion. Perhaps. The point is to point out the reason why the macro does not get expanded. The idea of passing the "name" of a function like macro as a parameter may not be obvious to all. > Caveat: You cannot safely use concatenation while using >BOOST_PP_EMPTY(). > >That's way too vague and general. I certainly can use concatenation >and BOOST_PP_EMPTY "together", for many reasonable definitions of that >word! I think you need to be more specific, or strike it. Agreed. >The BOOST_PP_ENUM_PARAMS example could benefit greatly from a >side-by-side format in a table showing the expansion on the right. There used to be a page that contained all the examples of the tutorial after preprocessing (and formatting). You could then simply click the title of the example to see the preprocessed code. >Showing not-even-correct details of BOOST_PP_REPEAT's implementation >doesn't help here. I'd strike it. You are probably right. I suppose when I wrote that, I wanted to give an idea to the reader how such macros might be actually be implementable (so that it doesn't seem as magical as it otherwise might). Looking back, I think that it was a mistake, because I have seen several people inventing their own REPEAT-style macros rather than using the generic macros in the library. Although, it might be the case even if the tutorial were different (nothing would have prevented those same people from looking at the actual implementation and learning the same information). >Furthermore, > > BOOST_PP_ENUM_PARAMS and its variations use BOOST_PP_REPEAT. > BOOST_PP_COMMA_IF(I) expands to a comma if I != 0. BOOST_PP_INC(I) > essentially expands to "I+1," and BOOST_PP_DEC(I) essentially > expands to "I-1.". > >I'd strike that too. You haven't said a word about BOOST_PP_INC/DEC >yet, so the reader is left wondering why you're giving their >implementation details. I agree that the comment should be removed. I think that the comment has probably been more relevant at some stage (CVS would probably reveal it if this was the case), but the context was lost during editing. That ''BOOST_PP_DEC(I) essentially expands to "I-1"'' is hardly an implementation detail. >Is this really better than iterating over a SEQ of categories in any >way other than efficiency? At the time when the example was written, SEQ had not yet been invented and even lists were not as efficient and convenient as they are today. Unfortunately, the example was never updated. Today, I would generally advocate using a sequence (or some other data structure). > Example - Use BOOST_PP_REPEAT to avoid O(n*n) repetition. > >It's unclear to me how that example avoids O(n*n) repetition. The point is to avoid manual, source code time, repetition and replace it with automated, preprocessing time, repetition. The code that you will edit after using REPEAT will be only O(1) (and not O(n*n)). It is the same as using a high level language to avoid programming in machine language. Sure, the compiler translates the high level code to machine language (well, not exactly, but close enough), but this doesn't mean that (because of the translation) you would not be avoiding programming in machine language as you seem to suggest. > Example - Use BOOST_PP_REPEAT for O(n*n) repetition. > >Or something? That might be a better way to convey the idea. > BOOST_PP_IF enables convenient generation of lists using > BOOST_PP_REPEAT. > >This statement, without an example, is too vague to be helpful. I agree. >Implementation details of BOOST_PP_IF don't help: > > How: BOOST_PP_IF is defined for the entire repeat range (psuedo code): > #define BOOST_PP_IF(c, THEN, ELSE) BOOST_PP_IF ## c(THEN, ELSE) > > #define BOOST_PP_IF0(THEN, ELSE) ELSE > #define BOOST_PP_IF1(THEN, ELSE) THEN > #define BOOST_PP_IF1(THEN, ELSE) THEN > ^ >especially since they appear to be wrong. Again, looking at an old version in CVS, this used to be correct. >I think the point is that BOOST_PP_IF works on first arguments other >than 0 or 1. If so, you should just say that it works on numeric >arguments up to N (whatever N is). That is probably a better way to put it. Again, the idea was to show how IF might actually be implemented (to dispell the magic), but it was probably a mistake. > Example: Use arithmetic, logical, and comparison operations when > necessary. > >With no commentary, and no generated code, this example is really >useless. I mean, of course you'd use arithmetic, logical, and >comparison operations "when neccessary". Looking at an old [...], there used to be a comment: "<P>The PREPROCESSOR library supports saturated arithmetic, logical and comparison operations on decimal integer literals in the range [0,BOOST_PP_LIMIT_MAG].</p> <p>Suppose that you want to generate a numbered lists with a special element inserted at a desired position. For example: E0, E1, S, E2. Consider the following example:</p>" The point of the example was really just to let the reader know that the library does contain macros for arithmetic, logic, etc... The example is admittedly weak and only designed to use some of the mentioned classes of macros. -Vesa Karvonen _________________________________________________________________ The new MSN 8: advanced junk mail protection and 2 months FREE* http://join.msn.com/?page=features/junkmail

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Re:[boost] Some remarks on PP docs
by Robert Ramey 10 Jun '04

10 Jun '04

David Abrahams wrote ..... While your at it, it would be really helpful to have a section for each compiler indicating which BOOST_PP... macros they don't support. I would hope this just be started and as users (like me) could just send in notes according to their experience. Here's the first line: BOOST_PP_CAT doesn't work with VC 6. Robert Ramey

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Re: [boost] Geometric Algebra Library
by Tim Stevenson 10 Jun '04

10 Jun '04

Hi Jaap, I'm very interested in something like your library. I've only just started to wrap my head around geometric algebra and I've been confining myself so far to just playing with simple problems on paper to see how it removes special boundary case handling for some simple algorithms. The computational complexity of the higher dimensions has always concerned me but it sounds like you are doing a lot of compile-time optimisation to save wasted calculations at run-time. In a few months I'm planning to devote a considerable amount of time to investigating Geometric Algebra in a lot more detail and your library sounds like a good tool to "play" with. I use both VC++ and GCC and I would be willing to devote some time to investigate porting your library to the latest version of GCC. Tim.

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