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[bjam] command for release/debug
by lcaminiti 14 Feb '12

14 Feb '12

Hello all, How can I program a Jamfile to execute the following on `bjam debug`: compile-fail const_block_err.cpp ; But the following on `bjam release`? run const_block_err.cpp ; Thanks. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-bjam-command-for-release-debug-tp4… Sent from the Boost - Dev mailing list archive at Nabble.com.

2 1

[filesystem] operations.hpp Won't Compile with VC10 using Boost 1.47
by Stewart, Robert 14 Feb '12

14 Feb '12

When I try to include boost/filesystem/operations.hpp, my code won't compile on MSVC 10 (Visual Studio 2010). The error is from boost/filesystem/v3/config.hpp:49: # if defined( BOOST_NO_STD_WSTRING ) # error Configuration not supported: Boost.Filesystem V3 and later requires std::wstring support # endif I found only the following places where BOOST_NO_STD_WSTRING is defined, and none should apply, so I'm at a loss to understand why my build fails. What have I missed? ./config/platform/amigaos.hpp:12:#define BOOST_NO_STD_WSTRING ./config/platform/symbian.hpp:85:# define BOOST_NO_STD_WSTRING ./config/stdlib/libstdcpp3.hpp:23:# define BOOST_NO_STD_WSTRING ./config/stdlib/modena.hpp:22:#define BOOST_NO_STD_WSTRING ./config/stdlib/sgi.hpp:100:# define BOOST_NO_STD_WSTRING ./config/stdlib/stlport.hpp:109:# define BOOST_NO_STD_WSTRING _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

2 1

[config] Flags for default/delete special member functions?
by Daryle Walker 14 Feb '12

14 Feb '12

Can we add macro constants to boost/config.hpp that indicate if marking (special) member functions as "= default" or "= delete" is supported? Daryle W.

2 1

[trunk] compilation errors on MSVC 8
by lcaminiti 14 Feb '12

14 Feb '12

Hello all, I get the errors below if I run bootstrap from the latest trunk checkout using MSVC 8 on Windows 7... (the trunk seems instead to work with GCC 4.5.3 on Cygwin). Thanks. --Lorenzo Setting environment for using Microsoft Visual Studio 2005 x86 tools. ### ### Using 'vc8' toolset. ### C:\Users\lorcam\Desktop\code\boost-trunk\tools\build\v2\engine>if exist bootstrap rd /S /Q bootstrap C:\Users\lorcam\Desktop\code\boost-trunk\tools\build\v2\engine>md bootstrap C:\Users\lorcam\Desktop\code\boost-trunk\tools\build\v2\engine>cl /nologo /RTC1 /Zi /MTd /Fobootstrap/ /Fdbootstrap/ -DNT -DYYDEBUG -wd4996 kernel32.lib advapi32.lib user32.lib /Febootstrap\jam0 command.c compile.c constants.c debug.c execnt.c filent.c function.c glob.c hash.c hdrmacro.c headers.c jam.c jambase.c jamgram.c lists.c make.c make1.c object.c option.c output.c parse.c pathunix.c regexp.c rules.c scan.c search.c subst.c timestamp.c variable.c modules.c strings.c filesys.c builtins.c md5.c pwd.c class.c w32_getreg.c native.c modules/set.c modules/path.c modules/regex.c modules/property-set.c modules/sequence.c modules/order.c command.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' compile.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' constants.c debug.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' execnt.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' filent.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' function.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' glob.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' hash.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' hdrmacro.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' headers.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' jam.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' jambase.c jamgram.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' lists.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' make.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' make1.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' object.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' option.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' output.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' Generating Code... Compiling... parse.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' pathunix.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' regexp.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' rules.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' scan.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' search.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' subst.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' timestamp.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' variable.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' modules.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' strings.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' filesys.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' builtins.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' md5.c pwd.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' class.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' w32_getreg.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' native.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' set.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' path.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' Generating Code... Compiling... regex.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' property-set.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' sequence.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' order.c c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2016: C requires that a struct or union has at least one member c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(466) : error C2061: syntax error : identifier 'pid_t' c:\users\lorcam\desktop\code\boost-trunk\tools\build\v2\engine\jam.h(468) : error C2059: syntax error : '}' Generating Code... -- View this message in context: http://boost.2283326.n4.nabble.com/boost-trunk-compilation-errors-on-MSVC-8… Sent from the Boost - Dev mailing list archive at Nabble.com.

3 3

Re: [boost] [optional] generates unnessesary code for trivial types
by Andrzej Krzemienski 14 Feb '12

14 Feb '12

> > But even that appears like a non-obvious thing to me. Would other people > > here in the list, and also developers in general agree that it is ok that > > you have output operation but no input operation? I think that in the > > standard library they always go in pairs. (I am not sure, though). > > In my own code I often find myself defining only output operators. For things > more complex than enums or numerics I usually handle input with specialized > solutions, with tools line Boost.Spirit. As for the standard library, I'm not > sure but dos thread::id have an input operator? > > Also, how would you implement it? what should an uninitialized optional > > print? Nothing? but how is having printed an uninitialized optional<int> > > different that not having printed anything? A question mark? but how would > > the following two be different: > > FWIW, boost::optional provides both input and output. > > If you propose to provide only output operation, then it looks like you > > want this for some sort of logging. But perhaps it is better to have some > > overloaded function toString() that converts all the types to strings. > > Usually the string format that works for one program does not work for the > > other. And there appears to be no natural/intuitive way of representing any > > type (like optional) as text. > > I usually dislike toString and alike methods. I think, manipulators are more > flexible and modularized approach. Do you think it would be possible to > provide different manipulators to fulfill different IO requirements? I have checked the standard and indeed thread::id provides operator<< without the matching operator>>, so this asymmetry would not be a precedent in the standard. Although the situation with thread::id is speciffic. ID's are assigned by the OS and trying to assign them by other means would definitely be an error. I also checked boost::optional and it provides both (I learned two new things today). Uninitialized optional of any type renders "--" (two dashes); whereas initialize optional always prepends a space. I am not sure if this does not look like hack; but people already said this would not be much of a problem. Certainly, there ways to make the output of optional configurable. I am not sure manipulators would be my preference. An alternative would be the approach that Boost.Date_time has adopted: you set your preference per stream (plus one global setting) by means of locale mechanism. However, when it comes to proposing stuff in front of the ISO committee, there is one other factor, which I failed to mention yet. It is the "fragility" of the process. I am concerned that if anything turns out to be controversial, the whole Optional would be at risk of being rejected. This might be an exaggeration (I have never gone through the process of proposing something and then pushing it through), but Optional has already been proposed by Fernando (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1878.htm) and rejected; primarily for two things: operators -> and * and the semantics for optional reference assignment (see http://lists.boost.org/Archives/boost/2005/10/95079.php) I would much like to avoid the situation where Optional (which I believe is very useful to wide variety of programmers) would be rejected because of one additional, however tiny, controversy of streaming operator. Regards, &rzej

3 2

Re: [boost] [optional] generates unnessesary code for trivial types
by Hite, Christopher 14 Feb '12

14 Feb '12

From: Domagoj Saric <domagoj.saric(a)littleendian.com> > > Maybe I'm missing something, but I don't see the justification. > IMO it seems that, yes, you are making the same mistake as Lucanus, thinking > about "The Universe" only as/through your POV of your personal problem domain: > a) (optional models optionally holding an object) + (objects can be held by > value and by reference) = optional<T&> perfectly logical I'm really not. Give me a use case. Do they make sense being passed as parameters/returns? Do they make sense being stored? I just see some corner case of optional being turned into a replacement for regular pointer. Why not just make dumb_ptr<T>? If you want you can make it streamable and give it clean construction. What is it you really want from optional<T&>? Does anyone use it a lot? Is it like std::vector<bool>? > b) creating special cases (e.g. for T&) creates special problems in generic code My point exactly. I'd make it work for completeness but not bother to optimize. Chris

4 6

Discovering C++11 lambda argument and result types to construct boost::function
by Frank Birbacher 14 Feb '12

14 Feb '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi! On comp.lang.c++.moderated I talked to Daniel Krügler about how to discover argument and result types from C++11 lambdas in a template context. The thread has the title "How to discover argument and result types from lambda for constructing std::function?" https://groups.google.com/d/topic/comp.lang.c++.moderated/qaMECIUlJp0/discu… The task is to provide a function template "make_function" that takes a C++11 lambda expression and returns a boost::function with the correct signature to call the lambda. This may be extended to accept any other callable type. Is there such a thing already in Boost? I'd like to add it. Would it go to Boost.Function alone? Or would parts fit into TypeTraits? Does Doug still maintain Boost.Function? Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: keyserver x-hkp://pool.sks-keyservers.net iEYEARECAAYFAk80RsMACgkQhAOUmAZhnmr5gACdGI6q9Xi1SbtpHs23GlAhU9uu Y3kAnjCpiZFGJp+IpnFVS3gmtZOqZp42 =GGdI -----END PGP SIGNATURE-----

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Re: [boost] [optional] generates unnessesary code for trivial types
by Andrzej Krzemienski 13 Feb '12

13 Feb '12

> I use optional references in my code, in cases like the following: > I have an operation, which processes some elements, and some of the > elements constitute special cases. The caller of the operation may or may > not want to know about the special cases that arose, so they can optionally > pass in a container which will be populated with the special cases: > void some_operation(inputs, optional<vector<case>&> special_cases = none) > { > for (...) > { > ... > if (special_case) > { > ... > if (special_cases) > special_cases->push_back(current_case); > } > } > } > Before I discovered optional, I used a plain reference, but that was annoying > because I had to create a dummy vector to be used as the default argument. > (The other alternative would have been to use a pointer, but then the caller > has to use the uglier syntax of passing in "&special_cases" rather than > "special_cases"). Nathan, going back to the same question I asked Andrey ( http://groups.google.com/group/boost-developers-archive/msg/704971a1eb63b3d2) it looks like your use case would still work if we disabled any sort of assignment for optional references (even the assignment from boost::none for resetting). Am I correct? Regards, &rzej

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Re: [boost] [optional] generates unnessesary code for trivial types
by Brian Wood 13 Feb '12

13 Feb '12

Andrzej Krzemienski: > But even that appears like a non-obvious thing to me. Would other people > here in the list, and also developers in general agree that it is ok that > you have output operation but no input operation? I think that in the > standard library they always go in pairs. (I am not sure, though). I haven't followed this closely, but don't see a problem with not being symmetrical here. The C++ Middleware Writer (CMW) has asymmetric support for Boost Range types: @out (boost::sub_range<std::vector<int32_t> >) If you omit the @out or write @in on that line, the CMW gives you an error message that ranges don't support receive (input) functionality. It only made sense to me to output via a range so that's all that's supported for now. -- Brian Wood Ebenezer Enterprises http://webEbenezer.net I'm happy Adele won all those Grammys. She deserves them them I think.

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Re: [boost] [optional] generates unnessesary code for trivial types
by Andrzej Krzemienski 13 Feb '12

13 Feb '12

> >> Side question: is streamablity going to be in your proposal? > > It is not currently. The reason for that is that there is no clear way how > > it should be implemented (a similar issue applies to pairs, tuples, > > variant, any, etc...) See > > http://lists.boost.org/Archives/boost/2005/03/81619.php<http://www.google.com/url?sa=D&q=http://lists.boost.org/Archives/boost/2005…>for discussion. I > > believe that the problem is with the streaming itself. For instance, should > > streaming out and then streaming the result back in produce the same value? > > Some people expect that, but even std::string could not provide this > > behavior. > > I'd do only << and forget about >> But even that appears like a non-obvious thing to me. Would other people here in the list, and also developers in general agree that it is ok that you have output operation but no input operation? I think that in the standard library they always go in pairs. (I am not sure, though). Also, how would you implement it? what should an uninitialized optional print? Nothing? but how is having printed an uninitialized optional<int> different that not having printed anything? A question mark? but how would the following two be different: optional<string> o1; // uninitialized optional<string> o2 = "?"; cout << o1; cout << o2; If you propose to provide only output operation, then it looks like you want this for some sort of logging. But perhaps it is better to have some overloaded function toString() that converts all the types to strings. Usually the string format that works for one program does not work for the other. And there appears to be no natural/intuitive way of representing any type (like optional) as text. Regards, &rzej

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