September 2005 - Boost-users - lists.preview.boost.org

Re: [Boost-users] Scons users?
by Merrill Cornish 14 Sep '05

14 Sep '05

Parveen, Thank you. That's an excellent factual reference. Merrill

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Beyond the C++ Standard Library: An Introduction to Boost
by Bjorn.Karlsson＠readsoft.com 14 Sep '05

14 Sep '05

Dear All, A long time ago, I came here--to the Boost developers and Boost users mailing lists--asking for help with reviewing a book about the Boost libraries. Your response was fantastic. Back then, I concluded my email with saying thanks to all Boosters; for the libraries, the ideas, the research, the discussions, and the enthusiasm. Today, when the book is finally shipping, I'd like to extend that thank you to the Boosters who helped make "Beyond the C++ Standard Library" reality. Beman Dawes, Rob Stewart, David Abrahams, Aleksey Gurtovoy, David Brownell, Douglas Gregor, Duane Murphy, Eric Friedman, Eric Niebler, Fernando Cacciola, Frank Griswold, Jaakko Järvi, James Curran, Jeremy Siek, John Maddock, Kevlin Henney, Michiel Salters, Paul Grenyer, Peter Dimov, Phil Boyd, Ronald Garcia, Thorsten Ottosen, Tommy Svensson, and Vladimir Prus; thank you all so much! I sincerely hope that I am giving something back to the amazing Boost community through this book. Best regards, Björn Karlsson

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Re: [Boost-users] Scons users?
by Sohail Somani 13 Sep '05

13 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Foster Gareth > Sent: Tuesday, September 13, 2005 10:47 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Scons users? > > > I suppose in terms of scons and boost, then next question is > how easy is it > to build rpm/deb packages etc when using these build systems? > Its very easy > with autotooled projects. I think this is an area where scons is lacking. Its great in building, but not so good at deployment.

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Putting together boost::any, mpl::vector, iterator::filter_iterator
by Stephen Gross 13 Sep '05

13 Sep '05

I've put together a class called 'AnyVector' for doing type-based iteration on a vector. The basic idea is that AnyVector wraps a std::vector<boost::any>. The AnyVector lets you iterate across a subset of the underlying vector by using filter_iterators. The filter iterators, in turn, dereference to the requested type for ease of use. For instance, you can do the following: === CODE === AnyVector<> a; a.push_back(1); a.push_back(std::string("hello")); a.push_back(2); a.push_back(std::string("goodbye")); for(AnyVector<>::Iterator<int> i = a.begin<int>(); i != a.end<int>(); ++i) std::cout << (*i + 5); for(AnyVector<>::Iterator<std::string> i = a.begin<std::string>(); i != a.end<std::string>(); ++i) std::cout << i->length(); ============ Furthermore, you can restrict (at compile-time) which objects are allowed to be inserted into the AnyVector. This is done by listing those types when you create your AnyVector: === CODE ==== AnyVector<int, std::string> a; // Only allows int's and string's a.push_back(3.5); // Fails at compile time - double's not allowed! ============= Would this be a useful addition to boost, or does it already exist somewhere in boost and I just missed it? --Steve Stephen Gross Case Western School of Medicine Cleveland, OH "By Grabthar's hammer, by the sons of Worvan, you shall be avenged." - Dr. Lazarus

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Filter_iterator and boost::any follow-up
by Stephen Gross 13 Sep '05

13 Sep '05

>I think you'll need to use something like: >for(filter_itr f(i.begin(), i.end()); f != filter_itr(i.end()); ++f) Ok, cool, I've got it working on a vector of ints. My next question is this: I've got a vector of boost::any's, and I want to iterate across only the boost::any's representing int's. For example: === CODE === template<typename T> struct isT { bool operator() (const boost::any & a) const { return a.type() == typeid(T); } }; int main() { std::vector<boost::any> av; av.push_back(1); av.push_back(std::string("hello")); av.push_back(2); typedef boost::filter_iterator<isT<int>, std::vector<boost::any>::iterator > int_itr; for(int_itr itr(av.begin()); itr != int_itr(av.end()); ++itr) ; } ========= Unfortunately, the above code seg faults when executed. I imagine I've probably constructed my filter_iterator incorrectly somehow. Any ideas? Thanks, --Steve Stephen Gross Case Western School of Medicine Cleveland, OH "By Grabthar's hammer, by the sons of Worvan, you shall be avenged." - Dr. Lazarus

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Newbie question on filter_iterators
by Stephen Gross 13 Sep '05

13 Sep '05

Ok, I'm trying to learn the basics of filter_iterators. I've got a vector of ints. I want to iterate across the vector and print out every positive value in the vector. Currently, my code doesn't work because g++ doesn't like me assigning a vector::iterator to a filtered_iterator. Obviously, I've missed some crucial point on how the filtered_iterator is supposed to work. The example code in the boost library doesn't really address this specific use. Can someone show me how to make the code below work as intended? Thanks in advance, --Steve ==== CODE FOLLOWS ==== struct is_positive { bool operator() (int i) { return i >= 0; } }; int main() { std::vector<int> i; i.push_back(-5); i.push_back( 5); i.push_back(-4); i.push_back( 4); i.push_back(-3); i.push_back( 3); i.push_back(-2); i.push_back( 1); typedef boost::filter_iterator<is_positive, std::vector<int>::iterator> filter_itr; for(filter_itr f = i.begin(); f != i.end(); ++f) { std::cout << *f << std::endl; } return 0; }

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Re: [Boost-users] Scons users?
by Foster Gareth 13 Sep '05

13 Sep '05

I suppose in terms of scons and boost, then next question is how easy is it to build rpm/deb packages etc when using these build systems? Its very easy with autotooled projects. Don't get me wrong, I hate autotools, hence my interest in alternatives. Hopefully these comments aren't dragging us off topic here - these could be reasons to use Scons over Boost Build I suppose - depends on the answers really. Cheers, Gaz > -----Original Message----- > From: Sohail Somani [mailto:s.somani@fincad.com] > Sent: 13 September 2005 18:19 > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Scons users? > > > -----Original Message----- > > From: boost-users-bounces(a)lists.boost.org > > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > > Foster Gareth > > Sent: Tuesday, September 13, 2005 9:37 AM > > To: boost-users(a)lists.boost.org > > Subject: Re: [Boost-users] Scons users? > > > > > > How does scons fair in terms of pulling in other libraries? I > > have used Autotools and using anything from there that > > doesn't have pkg-config support (like boost, opengl etc) is a > > nightmare. > > I believe scons can parse pkg-config output out of the box and set up > your CFLAGs etc appropriately but my mileage with this has varied > immensly. Anyway, its very simple to do it yourself as you have a real > programming language available. > > I think scons could learn a bit from autotools though I guess > autotools > is only useful because its popular. > > Sohail > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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Re: [Boost-users] Scons users?
by Sohail Somani 13 Sep '05

13 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Foster Gareth > Sent: Tuesday, September 13, 2005 9:37 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Scons users? > > > How does scons fair in terms of pulling in other libraries? I > have used Autotools and using anything from there that > doesn't have pkg-config support (like boost, opengl etc) is a > nightmare. I believe scons can parse pkg-config output out of the box and set up your CFLAGs etc appropriately but my mileage with this has varied immensly. Anyway, its very simple to do it yourself as you have a real programming language available. I think scons could learn a bit from autotools though I guess autotools is only useful because its popular. Sohail

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Re: [Boost-users] [BULK] Re: [BULK] [filesystem] function todetermineavailable space
by Sohail Somani 13 Sep '05

13 Sep '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of me22 > Sent: Monday, September 12, 2005 4:36 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [BULK] Re: [BULK] [filesystem] > function todetermineavailable space > > > On 12/09/05, Sohail Somani <s.somani(a)fincad.com> wrote: > > What about using a type that guarantees a certain amount instead of > > just "max" (which may vary)? Or equivalently, are we > guaranteed that > > uintmax_t can hold, say one TB, on any platform that boost supports? > > > > Even 1 TB isn't really safe. I know a number of people with > more total storage than that. > > How about a double? The imprecision shouldn't be a worry -- > if you're beyond the range of a double's precision for free > space then being off by even a few MB it doesn't matter and > doubles are perfectly precise for small integral numbers. ( > on x86 linux it seems my 64-bit doubles have 53 bits of > mantissa meaning they're perfectly precise for anything less > than 8192 TeraBytes. I don't know what the standard specifes > though, and my 32-bit floats are only perfectly precise for > under 16 MB. That being said, even the 32-bit float has a > max of over 3e26 TB, so just saying the precision of the > number returned is dependant on the precision of your > platform's double would get around that, assuming of course > we can assure that any rounding is done on the safe side. ) > > Also, the implementation could work internally in whatever it > wants to keep perfect precision and just feed out a double at the end. Great idea. I'm ok with this. What about platforms like linux or windows? What types do they use to report these stats?

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Re: [Boost-users] Scons users?
by Foster Gareth 13 Sep '05

13 Sep '05

How does scons fair in terms of pulling in other libraries? I have used Autotools and using anything from there that doesn't have pkg-config support (like boost, opengl etc) is a nightmare. > -----Original Message----- > From: Jon Stewart [mailto:stew1@ellipsis.cx] > Sent: 13 September 2005 17:30 > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Scons users? > > > On the Boost.Build list we were just discussing the fact that some > > people otherwise inclined towards Boost have chosen Scons over > > Boost.Build. It would be useful for us to understand some of the > > reasons why, if some of you wouldn't mind letting us know. > No flames, > > please! > > > I have been using Scons more for tiny projects* than for > large ones, and I > am still somewhat ignorant about Boost.Build, so I can't give a fair > comparison. But people aren't fair, so I think the data > points are still > valid: > > 1. Scons is a nice framework embedded in a general purpose > programming language. So, you get the benefit of a DSL that > does 80% of > the job very nicely, but you've got all that is Python for > the 20% that > doesn't fit -- and the two parts integrate naturally. I moved > from Ant to > Scons and liked that Scons provided lots of high-level > functionality but > didn't straightjacket me into abstractions that didn't fit my > situation. > > 2. My standard SConstruct file is 4 lines (2 imports, 2 > statements). I get > a full dependency analysis, can make full use of ccache and > distcc, and > run my unit tests after the build. I can't imagine life being > better. :-) > > 3. Boost.Build started out life as a fork (right?), and I > haven't noticed > many other projects outside of Boost using it. Scons seems to > have more > "momentum". > > 4. Boost.Build docs don't/didn't offer the trivial example of how > to get "Hello, World" to build. Compare: > > http://www.boost.org/tools/build/v1/build_system.htm#getting_started > > with: > > http://www.scons.org/doc/HTML/scons-user.html#AEN239 > > 5. A fair amount of traffic on this list seems to be from > people who have > trouble with Boost.Build. Of course, I'm not subscribed to > the scons users > list so this isn't fair, but my perception was that > Boost.Build would have > a steeper learning curve. > > I'm sure Boost.Build is a powerful system and can do the > job... it just > seemed to require more thought to get running the first time, > and I wanted > to devote my thought to writing code. > > Hope this helps, > > > Jon > > * The majority of my tiny projects are stub programs to play > around with > all the other Boost libraries! :-) > -- > Jon Stewart > stew1(a)ellipsis.cx > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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