July 2010 - Boost-users - lists.boost.org

Installation problems on Snow Leopard and EPD 6.2 32 bits
by Andrés Leonardo González Mancera 19 Jul '10

19 Jul '10

Hello all, I've been trying to install boost on a Mac Pro 8-core running the latest version of Snow Leopard, Xcode and Enthough Python Distribution (EPC 6.2 32 bits). I'm mainly interested in running pyCuda. I have followed the instructions available on: http://wiki.tiker.net/PyCuda/Installation/Mac/EnthoughtPython. Nevertheless, the address-model=32_64 gives an error for the python library and libboostpython doesn't get installed. What is strange is that the instructions seemed to have worked in a setup similar to mine. Has anyone been able to install Boost on a Mac using EPD 32 bits? Am I missing something obvious? Any help will be greatly appreciated. Andrés González Mancera, Ph.D. Profesor Asistente Departamento de Ingeniería Mecánica Universidad de los Andes Cra. 1 Este No. 19A-40 ML 625 Bogotá - Colombia + (571) 3394949 ext. 2915 angonzal(a)uniandes.edu.co

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type-safe printf
by Nathan Ridge 19 Jul '10

19 Jul '10

Hello, Does boost have a type-safe implementation of printf() using C++0x variadic templates? If not, where could I find one? Thanks, Nate. _________________________________________________________________ MSN Dating: Find someone special. Start now. http://go.microsoft.com/?linkid=9734384

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[variant] custom allocator support
by Alex Dubov 19 Jul '10

19 Jul '10

Greetings. I wonder, are there any plans (or general possibility) to extend variant<> to accept custom allocator, just like containers and lots of other stuff?

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[optional] boost improvement over std::map, the default initialization requirement
by alfC 18 Jul '10

18 Jul '10

Hi, The STL has an implementation of std::map<T1, T2>. It has some designs drawbacks in my opinion. For example, the fact that T2 has to have a default copy constructor. Even if for T2, by design, doesn't make sense to have a copy constructor. The problem boils down to the fact that, in the STL design, if an key element of the map is referenced with the operator[] and it doesn't exist then an 'empty' (default) object T2 is created. In my opinion this feature is independent of the other features of a map. For example if the element doesn't exists and the context is not assignment then it could give an exception. One option would be to use std::map<T1, boost::optional<T2> >. But I am not sure if that creates other problems. It at least creates the problem of having to access elements with the ugly syntax (*m[key]) The question is, does boost have another more complete solution for this problem? (something that I would call optional_map<T1, T2>, uninitializing_map<T1, T2>, elegant_map<T1,T2>) Thank you, Alfredo BTW, This is a simple implementation that I imagine, although in my opinion a clever implementation does not even need to use the indirection of boost::optional, because the context of assigment m[key]=val can be detected with template expressions, and only the copy constructor is needed in this case. (code not tested) template<class T1, class T2> class optional_map : protected std::map<T1, boost::optional<T2> >{ typedef std::map<T1, boost::optional<T2> > base; public: using std::map<T1, boost::optional<T2> >::size; using std::map<T1, boost::optional<T2> >::empty; T2& operator[](T1 const& key){return *base::operator[](key);} T2 const& operator[](T1 const& key) const{return *base::operator[] (key);} };

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boost parameter with template
by Kraus Philipp 18 Jul '10

18 Jul '10

Hello, I would like to write a class with static methods for calculating different distributions. The algorithmens of the distribution are complet, so now I would like to put them together. Finally I would like to have only one method for using the distribution call, like: template<typename T> static T getDistribution( const distribution&, <arguments> ) I have set distribution to an enum to check the kind of distribution (normal, uniform, bernoulli, ...), so I need for <arguments> a flexible number of arguments of float / double. I've test the cstdargs, but it isn't the right structure, so I have seen the "boost parameter", but I don't understand how to create a function within my class and create a template variable in it. My getDistribution function should have one fix parameter, the first, with a name of the distrivution, and 1 or 2 parameters which are optional with default values for the distribution. Is there a complete example how to use the boost parameter (a full source code)? Thanks Phil

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Odd limitation in Fusion design ?
by John Dlugosz 18 Jul '10

18 Jul '10

I see that the "Cons" sequence is Forward-only. reverse_view requires a Bidirectional sequence, at least. The for_each iteration function goes forward. However, hand-written recursive loop on a cons-like thing can do stuff before and other stuff after the recursive call to the cdr portion. Putting stuff "after" will give a reversed processing. So, in general, a reversed_for_each is not out of the question, and can be specialized for Cons when the general form of iterating backwards does not work. I also ponder that a more general form that indeed does stuff before AND other stuff after recursing the tail would be a useful addition. It might actually perform one operation iterating forward, then perform the other operation iterating backward back to the beginning; or use recursion; depending on the nature of the container. --John TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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[Serialization] Postpone saving
by Mailing Lists Controller 18 Jul '10

18 Jul '10

Hi, I'm working with the Serialization library and in detail with the xml archives. In my code I have to serialize a lot of classes and I wish to save in the xml file only when I've done with the serialization of all clasess, also I would like to have more control when the Serialization saves the file (do it raise exceptions when it save files? Which ones?). As far as I read from the tutorials when I use the operator<< in the xml_archive it save directly to the files. In my test I've seen that the archive have no problem to save many classes to the same archive however as I've wrote I would like to have more control (at least to know which errors appear during writing). Is it possible? Thank you for your time.

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How to fwd decl boost::variant (with type sequences)?
by Paul 17 Jul '10

17 Jul '10

In a large project (winxp, boost 1.38.0, 10K sources) we are using the boost::variant at some places. The variant types are visible to a large amount of cpp’s. Many of these source-file are not ‘using’ the variant at all, a small amount only ‘passes’ a variant type, and an even smaller amount actually uses it (copy, static-visitor, etc). We have noticed however that the compile-time increases for all sources-files, even when the variant is not used. On a single source-file its maybe split of a second extra but with 10K sources it quickly becomes problem. First attempt to solve this is to fwd declare the variant using provided header variant_fwd.hpp. Example: [v.h] #include <boost/variant/variant_fwd.hpp> class I001{ public: }; class I002{ public: }; class I003{ public: }; typedef boost::variant< boost::shared_ptr<C001>, boost::shared_ptr<C002>, boost::shared_ptr<C003> > v; [a.h] #include “v.h” class CA { public: void foo(const v& ref); }; Source-files now compile faster while only the sources that actually use the variant need to add #include <boost/variant/variant.hpp> to get the definition of the variant class. However it doesn’t really fit our needs because we need the ‘counted’ variant types (using typelists). Reasons for this is simply that some variants are only 3, 5 or 10 elements while another holds 39 element types. We don’t want to extend the length of each type to say 50. Therefore we first compose an mpl::vector (and even compose subsets using joint_view) before defining the variant types. Example of use: #include <boost/mpl/vector.hpp> #include <boost/variant.hpp> typedef boost::mpl::vector< boost::shared_ptr<I001>, boost::shared_ptr<I002>, boost::shared_ptr<I003> > MplV; typedef boost::make_variant_over<MplV>::type v; Now each cpp file must not only include the variant definitions again but also (part of) mpl. How could we solve this issue? One idea we had is to wrap the variant in a class and fwd decl that. Although it works I’m not sure if that is the way to go? Thanks for any advise, Paul

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[phoenix][units] make boost.phoenix play well with boost.units
by alfC 16 Jul '10

16 Jul '10

I have and expression of type arg1*arg1 which is contained in a deduced type LambdaExp (more preciselly composite<multiplies_eval,vector<argument<0>, argument<0> >) when trying to see what is the phoenix-deduced return type when input is double typename LambdaExp::template result<basic_environment<double> >::type naturally, it gives 'double' (double*double) but when the input type is a boost::units::quantity typename LambdaExp::template result<basic_environment<quantity<si::length> > >::type it gives: error_cant_deduce_type (instread of the equivalent of quantity<si::area>, like in quantity<si::area> a = quantity<si::length>()*quantity<si::length>() ) this is strange since it seemed that Phoenix worked out of the box with Units. What is going on? How can we help Phoenix deduce the return type? Does Phoenix need this help, like Boost.Lambda does by means of boost/ units/lambda.hpp? Thank you, Alfredo

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[fusion]push_back<list<>,int> > fails compilation
by Larry Evans 16 Jul '10

16 Jul '10

The code in the 1st attachment fails to compile as shown in 2nd attachment. If that's intended, the what's the justification for not allowing appending to an empty sequence? If that's not intended, then should I file a bug report? Based on: <fusion.doc>/html/fusion/algorithm/transformation/functions/push_back.html it seems push_back should work on a 'Forward Sequence' and based on: <fusion.doc>/html/fusion/container/list.html list is a 'Forward Sequence'. And based on the following quote from the Synopsis of the list.html: > The variadic class interface accepts 0 to FUSION_MAX_LIST_SIZE elements an empty list type, i.e. list<>, is a list, the attached code should compile. -regards Larry ###-*- mode: compilation; default-directory: "~/prog_dev/boost-svn/ro/trunk/libs/fusion/sandbox/" -*- Compilation started at Fri Jul 16 02:08:38 make HOW=gcc4_5n run install -d `dirname /home/evansl/prog_dev/boost-svn/ro/trunk/sandbox-local/build/gcc4_5n/boost-svn/ro/trunk/libs/fusion/sandbox/list_push_back.o` /home/evansl/download/gcc/4.5-20100624/install/bin/g++ -c -Wall -ftemplate-depth-300 -O0 -g3 -fno-inline -std=gnu++0x -I/home/evansl/prog_dev/boost-svn/ro/trunk -DTEMPLATE_DEPTH=300 list_push_back.cpp -MMD -o /home/evansl/prog_dev/boost-svn/ro/trunk/sandbox-local/build/gcc4_5n/boost-svn/ro/trunk/libs/fusion/sandbox/list_push_back.o list_push_back.cpp: In function 'void boost::fusion::sandbox::run()': list_push_back.cpp:25:45: error: no matching function for call to 'boost::fusion::joint_view<boost::fusion::list<>, const boost::fusion::single_view<int> >::joint_view(boost::fusion::result_of::push_back<const boost::fusion::list<>, int>::type)' /home/evansl/prog_dev/boost-svn/ro/trunk/boost/fusion/view/joint_view/joint_view.hpp:55:9: note: candidates are: boost::fusion::joint_view<Sequence1, Sequence2>::joint_view(Sequence1&, Sequence2&) [with Sequence1 = boost::fusion::list<>, Sequence2 = const boost::fusion::single_view<int>] /home/evansl/prog_dev/boost-svn/ro/trunk/boost/fusion/view/joint_view/joint_view.hpp:34:5: note: boost::fusion::joint_view<boost::fusion::list<>, const boost::fusion::single_view<int> >::joint_view(const boost::fusion::joint_view<boost::fusion::list<>, const boost::fusion::single_view<int> >&) make: *** [/home/evansl/prog_dev/boost-svn/ro/trunk/sandbox-local/build/gcc4_5n/boost-svn/ro/trunk/libs/fusion/sandbox/list_push_back.o] Error 1 Compilation exited abnormally with code 2 at Fri Jul 16 02:08:40

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