May 2004 - Boost - lists.preview.boost.org

Re: [boost] Re: static sized strings
by Reece Dunn 29 May '04

29 May '04

Rob Stewart wrote: >From: John Nagle <nagle(a)overbot.com> > > (And you have to supply conversions.) Most strings are sized a bit too > > big, anyway. > >Oh, it just occurred to me that when the two have the same size, >there should be a cctor and copy assignment operator to avoid the >virtual function call overhead. The cctor also fixes a bug that caused a pure virtual function run-time error with VC when you have the following: template< size_t n, … [View More]

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metacomm regressions: which borland version
by Vladimir Prus 28 May '04

28 May '04

The metacomm regression result show an error for borland compiler: http://tinyurl.com/2ql6s which reads: Assertion failed ..... config_file.cpp(144) : isTmplSpecSym(sym) .... I've just installed CBuilderX Personal, and tried to compile the library with that compiler. The interesting thing is that compiler has 5.6.4 as version string, the symbol __BORLANDC__ is defined to be 0x0564, but I don't get that error, and get some other errors. What could be the reason? - Volodya

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RE: Manaed C++ (was: [boost] Re: Re: [prereview request][fsm])
by Randy Bowen 28 May '04

28 May '04

> The next version of managed C++, circa 2005, has promised > support for C++ templates. > This is probably getting off topic for Boost, but: Are you sure on this point? My understanding was that there would be general support for "generics" in managed languages, but that this is specifically not the current the C++ template mechanism. Randy Bowen Stamps.com

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RE: [boost] static sized strings
by Reece Dunn 28 May '04

28 May '04

Martin wrote: >Not sure what the problem is but construction or assigment from operator+ >doesn't work int VC++2002. > >boost::fixed_string<20> xxx, yyy, zzz = xxx + yyy; > >gives the following error >[snip] The problem is that I need operator+ overloads for fixed_string: the obes for basic_string_impl will not work! I shall have a fix posted shortly. >And another thing: > >One of the find overloads doesn't check the pos argument so it might create >an … [View More]

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Should std::allocator::rebind be used with std::map?
by Andreas Huber 28 May '04

28 May '04

Dear Boosters Some old implementations of std::allocator don't provide the rebind member template (e.g. MSVC6.0 stdlib). This keeps code as the following from compiling: typedef std::map< const state_base_type *, event_queue_type, std::less< const state_base_type * >, typename allocator_type::template rebind< // *** here *** std::pair< const state_base_type * const, event_queue_type > >::other > deferred_map_type; However, this map … [View More]

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Re: [boost] Re: static sized strings
by Reece Dunn 28 May '04

28 May '04

Rob Stewart wrote: >From: "Reece Dunn" <msclrhd(a)hotmail.com> > > John Nagle wrote: > > > The big question is whether the size specified in the > > >declaration (as in "char_string<80>") includes the > > >trailing null. > > > > > I have modified the sandbox implementation to make it easy to switch >between > > the two models; it is currently using the 2nd model (adding space for >the > > null). One possibility … [View More]is putting the choice of models as a template > > parameter (e.g. bool need_null -- see comments in the sandbox code for >an > > implementation), that way the decision is up to the programmer and not >the > > library implementor. > >This is overkill. I think you misunderstand what I am trying to say. See my comments below. >The purpose of fixed_string is to replace >arrays of characters, otherwise, std::string would be the right >replacement, right? correct. >Given that assumption, look to the syntax you're replacing: > > char s[] = "1234567890"; > assert(10 == strlen(s)); > size_t const LENGTH = 3; > char t[LENGTH + 1]; > strncpy(t, "ABCEFGHIJKLMNOP", LENGTH); > assert(LENGTH == strlen(t)); > >Now do the same with the new class: The equivalent would be: fixed_string< 15 > s( "1234567890" ); // [1] assert( 10 == strlen( s )); // C-style assert( 10 == s.size()); // C++-style const size_t LENGTH = 3; fixed_string< LENGTH > t; // [2] t = "ABCEFGHIJKLMNOP"; assert( LENGTH == strlen( t )); // C-style assert( LENGTH == t.length()); // alternate C++-style [1] You need to specify the size of the buffer. You cannot declare an object of type fixed_string_base (as it is abstract), you can only have references and pointers to it so you can operate on variable-capacity strings. [2] This is the point that we are discussing. Should this line be: fixed_string< LENGTH > t; as will work with the current sandbox implementation (my suggestion #2), or should it be: fixed_string< LENGTH + 1 > t; as in my suggestion #1. The code calculates the correct storage and capacity values at the top of the fixed_string class, because buffer overrun checks rely on these values: template< size_t n, typename CharT = char, class CharStringPolicy = std::char_traits< CharT > > class fixed_string: public fixed_string_base< CharT, CharStringPolicy > { BOOST_STATIC_CONSTANT( size_t, storage_c = n + 1 ); // = needs_null ? n + 1 : n BOOST_STATIC_CONSTANT( size_t, capacity_c = n ); // = needs_null ? n : n - 1 // ... }; Different programmers favour the different semantics, so I ask: why not parameterise it, providing a default behaviour. >(I know there is no make_fixed_string() -- yet -- but such a >facility would be appropriate.) Er... the fixed_string constructors! When you declare the object, you should know the size of the buffer you are using, e.g.: fixed_string< 100 > data; but when operating on them, you want to use any capacity buffers, so you either need a template (not good for existing code or code that needs to be in a static/dynamic library), so you use fixed_string_base, or [w]char_string if you want to save typing :). E.g. inline size_t strlen( const char_string & s ) { return( s.length()); } >I think this clearer reveals that fixed_string's size parameter >should specify the number of characters. Remember, one can use >boost::array to manage a fixed size, non-string buffer. If >buffer overrun protection is insufficient in boost::array, that >should be fixed (or a new class should be added to Boost). Thus, >fixed_string can ignore that usage. This is not what we are discussing. See above. The need_null name was to indicate that an extra charcter be reserved for the null, not whether to add a null terminator or not. Sorry for the confusion. I have started work on documentation, but it is currently in text form. I will post the documentation in BoostBook format within the next day or so. Regards, Reece _________________________________________________________________ Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger [View Less]

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RE: [boost] input_iterator_facade (was: Re: [iterator facade] Why is dereference const?)
by Rozental, Gennadiy 28 May '04

28 May '04

> I still don't understand which design, yours or mine, is better. It seems mine > allows to create iterators with smaller number of lines, but maybe there's > something else. Why do you think so? I would say vice versa, since I do not require constructor in derived class to call found_eof(). Gennadiy.

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RE: [boost] Re: static sized strings
by Reece Dunn 28 May '04

28 May '04

John Nagle wrote: >Reece Dunn wrote: >>Different programmers favour the different semantics, so I ask: why not >>parameterise it, providing a default behaviour. > > As with "do we null-terminate", I think we have to pick a >behavior and stick to it. I could live with either set of >semantics, but adding a parameter makes the issue more confusing. >(And you have to supply conversions.) Most strings are sized a bit too >big, anyway. Ok. I'll stick with the … [View More]

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static sized strings
by Martin 28 May '04

28 May '04

Not sure what the problem is but construction or assigment from operator+ doesn't work int VC++2002. boost::fixed_string<20> xxx, yyy, zzz = xxx + yyy; gives the following error error C2679: binary '=' : no operator found which takes a right-hand operand of type 'boost::detail::basic_string_impl<Base,ErrorPolicy>' (or there is no acceptable conversion) with [ Base=boost::detail::fixed_string_iface<char,std::char_traits<char>>, … [View More]

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including external libraries
by Andreas Beyer 28 May '04

28 May '04

I am using boost with mingw. How do I tell bjam to bind with an additional (non-boost) library? In my case I would like to bind msvcp60.dll or libmsvcp60.a into my project. The latter file is in mingw's lib-path. Thanks, Andreas

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