November 2006 - Boost-users

Best practices for boost:signal
by Memfis 15 Nov '06

15 Nov '06

What is the best practice for using boost::signal? Should the signal be a public field? Should an accessor method be used? Should there be some special connection methods for every signal, like the following: private: signal<void()> x; public: void connectX(const signal<void()>::slot_type& slot); void disconnectX(const signal<void()>::slot_type& slot); If you use boost:signal, how do you do it? (Okay, actually connectX should return a connection object and disconnectX should take the it as its parameter, but it's about the general idea) -- Memfis

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[mpl::map] Still problems with map
by Ovanes Markarian 15 Nov '06

15 Nov '06

Ji Dave, Hi Alexey, It seems that at least macro definition for the map of 150 tuples worked. Now I face a new problem. To reduce compilation times we decided to use map10, map20 etc. Unfortunately as we found out this will not compile if I pass to map10 only 7 arguments. With unnumbered map these elements were default initialized with "na" type. Why isn't this the case with numbered maps? I get the following g++ errors: /path/fname.hpp:5945: error: wrong number of template arguments (4, should be 10) /user/some_uname/projects/libs/boost/include/boost/mpl/map/aux_/preprocessed/typeof_based/map10.hpp:141: error: provided for `template<class P0, class P1, class P2, class P3, class P4, class P5, class P6, class P7, class P8, class P9> struct boost::mpl::map10' I assume that the macro generation was successful if I receive the error: /path/fname.hpp:11036: error: wrong number of template arguments (71, should be 150) /user/some_uname/projects/libs/boost/include/boost/mpl/map/aux_/numbered.hpp:41: error: provided for `template<class P0, class P1, class P2, class P3, class P4, class P5, class P6, class P7, class P8, class P9, class P10, class P11, class P12, class P13, class P14, class P15, class P16, class P17, class P18, class P19, class P20, class P21, class P22, class P23, class P24, class P25, class P26, class P27, class P28, class P29, class P30, class P31, class P32, class P33, class P34, class P35, class P36, class P37, class P38, class P39, class P40, class P41, class P42, class P43, class P44, class P45, class P46, class P47, class P48, class P49, class P50, class P51, class P52, class P53, class P54, class P55, class P56, class P57, class P58, class P59, class P60, class P61, class P62, class P63, class P64, class P65, class P66, class P67, class P68, class P69, class P70, class P71, class P72, class P73, class P74, class P75, class P76, class P77, class P78, class P79, class P80, class P81, class P82, class P83, class P84, class P85, class P86, class P87, class P88, class P89, class P90, class P91, class P92, class P93, class P94, class P95, class P96, class P97, class P98, class P99, class P100, class P101, class P102, class P103, class P104, class P105, class P106, class P107, class P108, class P109, class P110, class P111, class P112, class P113, class P114, class P115, class P116, class P117, class P118, class P119, class P120, class P121, class P122, class P123, class P124, class P125, class P126, class P127, class P128, class P129, class P130, class P131, class P132, class P133, class P134, class P135, class P136, class P137, class P138, class P139, class P140, class P141, class P142, class P143, class P144, class P145, class P146, class P147, class P148, class P149> struct boost::mpl::map150' Many thanks for your kind help. With Kind Regards, Ovanes Markarian

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[boost-users][fusion] tuple + io question
by David Klein 15 Nov '06

15 Nov '06

Hi, Is there a reason why fusion/tuple/tuple.hpp includes fusion/sequence/io.hpp? The "normal" boost::tuple, is split into tuple/tuple.hpp and tuple/tuple_io.hpp. I have the problem that just including *stream headers, make my program crash before main, because they rely on static variables that dynamically allocate memory, which isn't available before main. I fixed this for me by commenting out the include line, and now i'm only just wondering why this differs to boost::tuples? -- regards, dave

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[Boost.MultiArray] So many warnings
by Evgeny Yashin 15 Nov '06

15 Nov '06

Hi guys. Just started to use library, and.. #include "boost/multi_array.hpp" void f() { boost::multi_array<int, 2> arr; arr.resize( boost::extents[2][2] ); } Why so many warnings (5 warnings)?? warning C4267: '=' : conversion from 'size_t' to 'boost::const_multi_array_ref<T,NumDims,TPtr>::index', possible loss of data .... Can it be fixed?

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Using assign::map_list_of for complex types
by Hughes, James 15 Nov '06

15 Nov '06

Hello all, I've been trying to create an initiliser for the following (paraphrased) struct data { Char *str; Vector<int> stuff; }; map<int, struct data> mapstuff = map_list_of (1, ("hello", list_of (3) (4) (2)), (3, ("goodbye", list_of (1) (3) ); Etc etc However, this doesn't work, with a very complex compile error from assign. I've tried also... map<int, struct data> mapstuff = map_list_of (1, {"hello", list_of (3) (4) (2) } ), // note curly braces (3, {"goodbye", list_of (1) (3) ) } ); But that doesn't work either. Is it actually possible to do something like this, and if so, how? James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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Errors compiling Boost.Python library on Solaris
by chris botos 15 Nov '06

15 Nov '06

Hi, I'm new to this list and to Boost. I'm interested in using Boost to wrap C++ objects in Python. The environment is Solaris 10, x86. I did the following: Downloaded boost_1_33_1.tar and extracted it to /opt/boost. >setenv PYTHON_ROOT /usr/local > cd to /opt/boost/boost_1_33_1/libs/python/build > bjam I get lots of error messages, repeated throughout the compile and tend to be grouped and refer to the same line: '->' cannot appear in a constant-expression '&' cannot appear in a constant-expression template argument 1 is invalid value is not a member of '<declaration errors>' ...failed gcc-C++-action ... is also associated with the above If I "bjam" from /opt/boost/boost_1_33_1, I get the same errors when it gets to the python library. I would most appreciate any help with this! Regards, Chris Botos

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comparing map's key and sorted vector
by Maitre Bart 15 Nov '06

15 Nov '06

Suppose I have a map (m) and a sorted vector of strings (v). The map's key is a string, and the map's value is foobar. I wish to compare map's keys with the vector's values and detect if they all match: (*mit).first == *vit and wish to do it with STL/Boost algo and functors. So I am starting with this: equal(m.begin(), m.end(), v.begin(), boost::bind(std::equa_to<string>(), std::select1st<std::pair<string,foobar> >(_1), _2)); I know 2 parameters are past to bind: *mit and *vit . However, before the equality, I want to extract the key from the map iterator (i.e. (*mit).first) before the comparison. That is this part I have difficulty to concretise. Btw, is there any equivalent to select1st (SGI extension) in Boost? Does anyone have any idea? I must be close to the solution...

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[OT] Strange Subject Line Problem with this Mailing List
by Wu Yinghui, Freddie 14 Nov '06

14 Nov '06

Hi all, Sorry for this post, as it is not related to Boost, but to this mailing list instead. I've been seeing subject lines in a mess for "Re:" posts as illustrated below: ==== snip ==== > Today's Topics: > > 1. BGL: Bundled Properties in subgraphs (Greg Reynolds) > 2. Re: [Serialization] a couplacrashesfromhiearchycomplexity > (Reusser, Edward) ==== snip ==== As seen above, the subject line of the second post was unreadable to me without spending a fair amount of efforts. Has anyone checked out what was the cause of this problem yet? Cheers, Freddie -- Wu Yinghui, Freddie Research & Development Senior Software Engineer Volume Interactions Pte Ltd 1 Kim Seng Promenade, #12-01 Great World City East Tower Singapore 237994 Tel: +65 62226962 (Ext 216) Fax: +65 62226215 Email: yhwu(a)volumeinteractions.com URL: http://www.volumeinteractions.com Important: This message is intended for the recipient(s) addressed above. It contains privileged and confidential information. If you are not the intended recipient, please notify the sender immediately by replying to this message and then delete it from your system. You must not read, copy, use, or disseminate this communication in any form. Thank you.

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[serialization] Richer "tagged" fields and polymorphic archive types
by Caleb Epstein 14 Nov '06

14 Nov '06

Robert, First let me start off by thanking you for the excellent Boost Serialization library. I'm planning to use it as part of a new system I'm building at my place of work as a more flexible replacement for Rogue Wave's "saveGuts/restoreGuts". I've been able to implement my own archive types without too much of a struggle, and have been overall very impressed with the functionality of the library and its documentation. Now some background and then on to the questions :) I'm not sure if you are familiar with TIBCO's "Rendezvous" messaging middleware product (http://tibco.com/) or with the FIX protocol (http://fixprotocol.org/) but these are both commonly used in financial services applications. Rendezvous as a messaging transport and FIX as a general message convention and data dictionary. FIX also specifies a "session" layer used for communication, but thats out of scope here. Both Rendezvous (RV) and FIX support the concept of numeric field identifiers in their messages. In FIX, serialized messages look like TAG=VALUE\x01TAG=VALUE\x01... where TAG is an integer field ID and VALUE is the value associated with that tag and \x01 is an ASCII SOH character. In RV messages, fields may be given a name and/or an integer field ID. So it is pretty straightforward to represent a FIX message as an RV message (or vice-versa) if you always use these numeric IDs. Also, these "tagged" message formats facilitate interchange of data between different systems because they do not place stringent requirements on field ordering or even field presence in some cases. In the system I'm working on, the fundamental object types can all be mapped more or less directly to messages in the FIX specification. OK, so now onto the meat of the question. What I'd like to use in this application is something akin to NVP serialization for my objects, but which I'll call FIELD serialization. Every member of an object can be associated with a FIELD ID which would contain both a name and an integer ID (e.g. "Price" and 44). The universe of field IDs is more or less static and well-known. To this end I've created two utility classes called field_id and field. The field_id class is a std::pair<int, const char*> and the template field class is a std::pair<const field_id*, T*> not unlike the nvp class. It provides methods to get the field's name, id, and value. There is also a template utility function "make_field(const field_id&, T&)" that creates a field object in the same way "make_nvp" creates an nvp. I have implemented a "tibco_oarchive" that provides a template "save_override(const field<T>&, int)" method, and this works fine if I am using template<typename Archive> serialization methods with my archive definition in scope, and if I write my serialization code using "make_field" instead of "make_nvp". But this, naturally, does *not* work if I try to use polymorphic archives, since the base classes here do not know anything about my "field" template, only "nvp". Additionally, my template-based serialization code will fail to compile with archive types that don't provide "save_override"s for my "field" template, which is all of the "standard" archive classes. What I'd like is to figure out some way to implement this tagged-field serialization scheme in a way that would be compatible with the polymorphic archive interface and that would (ideally) still compile with the existing archive implementations that don't know about my "field" class. This latter requirement is less important. The reason I'm leaning toward the polymorphic archive interface is that I'm sure we will need to adopt new wire-formats and middleware interfaces in the future. Keeping all the object serialization code in a library that doesn't require recompilation will make this process very easy. So, do you think you could offer any suggestions on how I might go about achieving this? Let me know if you need more information or clarification, and thanks for your help. -- Caleb Epstein

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Sequence of Types, What For?
by Terry G 14 Nov '06

14 Nov '06

I've just finished reading C++ Template Metaprogramming again. I just don't get it. Why would someone use a type container? I have used enable_if, along with some of the logic functions for managing an overload set. Otherwise, I'm clueless. I'd really like a reference to an MPL primer or some case studies. Too much pain with very little gain. Time to ask for help. Rereading this, it sounds negative. Really, I think the MPL is really cool! terry

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