December 2004 - Boost - lists.boost.org

mailing lists archives stuck
by Joaquín Mª López Muñoz 22 Dec '04

22 Dec '04

To whom it may concern, the archives of the mailing lists, (for instance, http://lists.boost.org/MailArchives/boost/bydate.php) have stopped collecting messages since almost a week. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Add conversion op doc to scoped_ptr
by cliffg＠codewrangler.net 22 Dec '04

22 Dec '04

This may already be known / in the queue / in CVS, but in case not ... The scoped_ptr synopsis and members does not document the unspecified-bool-type conversion operator that scoped_ptr provides (I didn't check scoped_array to see if the same issue is present or not.) I found this when a couple members of my team converted code from shared_ptr to scoped_ptr, with the original code relying on the conversion operator, and I was surprised when everything compiled cleanly (without adding the appropriate get() calls). Cliff

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Help \ Advice requested on getting the return type from a Lambda fctor
by Brian Braatz 22 Dec '04

22 Dec '04

I wrote up the simple example that shows what I am trying to figure out Basically, I am trying to pull the deduced return type (or explicitly passed as a template param in lambda bind()) in my template. If I have a function that is receiving a functor, I would like to be able to take that functor and pull the RETURN TYPE out of it. Lets say I have a function that returns a string: std::string ReturnAString() { return "this is a string"; } And then here is my template function (code below does not compile) template < typename TFUNCTOR> TFUNCTOR::result_type CallFctorDeduceRet( TFUNCTOR & functor) { return functor(); } Now here is my bind call std::cout << ( bind<std::string>(&ReturnAString)); Is there a way to GET to the return type in the Lambda fctor that was generated with a BIND call? I would like to be able to pull the <std::string> from the bind call and use it in the template function. It is not a problem for my template function to be dependant upon lambda bind. I have been going through the lambda code. And while it is brilliant, I am having a bit of difficulty figuring out what I am looking at (grin). Any help or direction is greatly appreciated FULL SAMPLE CODE HERE: template <typename CURRIEDTYPE> // Id class for currying type without creating the object class Id { public: typedef CURRIEDTYPE TYPE; }; // Explictly pass IN a return type template < typename TFUNCTOR, typename TRET> TRET CallFctorPassInRet ( TFUNCTOR & functor, Id<TRET> & ) { Id<TRET>::TYPE TRet; TRet = functor(); return TRet; } std::string ReturnAString() { return "this is a string"; } // try to get return type from the lambda fctor // Below does not compile- but it is along the lines of what I // WANT to do- note that I am trying to get from the Lambda functor the deduced return type template < typename TFUNCTOR> TFUNCTOR::result_type CallFctorDeduceRet( TFUNCTOR & functor) { return functor(); } void Test_LambdaRetDeduction() { std::cout << "CallFctorPassInRet returns [" << CallFctorPassInRet( bind(&ReturnAString), Id<std::string>()) << "]" << std::endl; // below is what I want to make work std::cout << "CallFctorDeduceRet returns [" << CallFctorDeduceRet( bind<std::string>(&ReturnAString)) << "]" << std::endl; }

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boost.sourceforge.net hacked?
by Joaquín Mª López Muñoz 22 Dec '04

22 Dec '04

Please take a look at http://boost.sourceforge.net/regression-logs/ ??? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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RE: [boost] Unzipping the Boost distro
by Stefan Seefeld 22 Dec '04

22 Dec '04

> From: Richard Peters [mailto:r.a.peters@student.tue.nl] > If some boost authority certifies the released packages, and > users correctly > verify that the certificate is issued by the boost authority, and the > certificate is valid on the package, then certified executables can be > trusted as well. You are right, providing certificates is one thing. Whether or not to distribute executable self-extracting packages is different question. Regards, Stefan

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RE: [boost] Unzipping the Boost distro
by Stefan Seefeld 22 Dec '04

22 Dec '04

> From: Richard Peters [mailto:r.a.peters@student.tue.nl] > Another argument that I thought of this morning: suppose we > do not publish a > self-extracting executable. What is going to stop an attacker from not > uploading his own self-extracting look-alike? If he can > change existing > archives, he probably can add other archives as well. right, but if some boost authority certifies its released packages, everybody is free to ignore such look-alikes. Isn't that the whole point of certification ? Regards, Stefan

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automatic garbage collecting algorithm and its implementation in c++
by yilin yang 22 Dec '04

22 Dec '04

hi, everybody i've just designed and coded a garbage collecting infrastructure named u_canforget. it was uploaded onto the news group at boost.yahoo. the main idea is that we count the reference to track the life-cycle of the given object. as the new operator was overloaded to statisfy this requirement. the other important concept was the reference object. with the syntax represented by the redefined macros, the codes may be written in a very simple way with relationships automatically constructed, objects are freed without delete operater can be realized as well. i would keep tracking this thread, if there are any thought about this algorithm. thx for your advices. your's yilin. --------------------------------- Do You Yahoo!? 注册世界一流品质的雅虎免费电邮

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[gui] Representation of graphical objects
by Reece Dunn 22 Dec '04

22 Dec '04

Hi All, A GUI library can be thought of as having two distinct, but related, units: components (GUI widgets) and graphical objects/operations. A GUI component consists of data and events (e.g. a push button has a title and an onpressed() event). The question is: how do we represent the graphics unit? There are clearly two views: high level and low level. You can represent a graphics library as a series of objects (lines, circles, polygons, images, text, etc.) each of which having a set of properties (color, background/fill color, etc.). This is a high-level view and is based on the vector graphics model. Consider you are writing an application that draws a fractal object on the screen such as a Hilbert curve. You decide to represent it as a list of line objects. What happens when you redraw the curve? For large numbers of lines (easy when you have a fractal depth of 5+), the redrawing process is going to be slowed down. This is because you will be changing the colour on each line drawing operation. This becomes more apparent if you are using images to fill polygons and are using the same fill pattern across several objects. There are various graphics primitives (font, pen, fill (i.e. brush), etc.). Each primitive operates on a canvas and some can be used to query information on a device (e.g. the area occupied by a text string). In Windows a device and canvas are represented the same (as a HDC), but it makes sense to distinguish between them: you draw to a canvas and query information about a device. These graphical primitives should form the core of the graphics unit, with the high-level graphical objects being viewed as an extended unit. With the discussion on using CSS and Andy Little's comment about what difference is there between GUI components and graphical objects in terms of them both being objects that have position information and are drawn onto a canvas, it makes sense to allow both types to share a common interface. The main question is really what happens on the redraw phase? Ideally, components should not be drawn on the ondraw event, but rather be controlled by the behaviour of the operating system. For owner drawn components, do we handle the drawing event here or on the request of the OS (I think the latter is best). What about lightweight components (i.e. components that do not take up OS resources w.r.t. component representation, but that do support an event model)? Should we treat lightweight controls as graphical objects with an event model? Do graphical objects support an event model? Should graphical objects be treated as lightweight components? Regards, Reece

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Unzipping the Boost distro
by David Abrahams 22 Dec '04

22 Dec '04

I just downloaded boost-1.32.0 and started to unzip it with the built-in facilities in Windows XP; the OS reported it was going to take 50 minutes and it was *crawling*. Using cygwin's unzip tool it was done in under a minute. I'm thinking we should stop distributing raw .zip files without an extractor... -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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regex library design (was: any interest in finite automata-based regex engine?)
by Vladimir Pozdyayev 22 Dec '04

22 Dec '04

John Maddock wrote: > This is an area I want to explore though, if I can get this next lot of code > out the door, then I'll create a cvs branch to experiment with this, if you > want to suggest / experiment with a design for the abstract creator in the > meantime, then go for it. Finally I got down to refactoring the ANFA code. Take a look at http://groups.yahoo.com/group/boost/files/anfa-regex/anfa091.zip (once again, this is not a fullscale regex library... yet) The DESIGN file content is appended to this message. -- Best regards, Vladimir Pozdyayev. ---------------------------------------------------------------------- -= Regex Design Issues =- The core classes. * charset Provides "bool operator( character )". Nothing much to say apart from that, but do see the Charset Issues section. * charset creator Supports arbitrary charset expressions (within the limits of a given set of possible operations). Implementations, however, are not required to provide _all_ the declared functionality; calls for unsupported features should result in appropriate exceptions. Also provides the "void create( charset & )" function which is used to initialize a charset newly created by "matcher creator". The "abstract_charset_creator" class provides stubs for all expression elements possibly to be requested by regex parsers. Implementations with limited functionality can inherit them and redefine only those functions that should actually do something useful. * matcher Provides the low-level matching functionality, say, finding the first occurrence of bla-bla-bla. On the other hand, replacing all occurrences is a high-level action, for it consists of (1) finding them and (2) creating a modified string---so it should go into the "regex" class. (On the other other hand, if it is possible to do replacement on the fly while searching, this becomes a low-level action. I don't know if it can be done in a sufficiently general way, however.) * matcher creator Like charset creator, only for matchers. * parser The syntax parser. Takes the input string in the form of begin-end iterators, and issues a sequence of charset/matcher creator calls ending with "matcher_creator::create" (or an exception). In essence, simply provides the function "void parse( matcher &m, iterator begin, iterator end )". A parser must be consistent with the properties of "creator" classes. * regex A wrapper for the "matcher" class. Provides the high-level creation & utilization routines. How they are connected. A sample from "regex.cpp": typedef basic_regex< basic_simple_parser< basic_charset_creator< wchar_t >, basic_anfa_matcher_creator< basic_charset< wchar_t > >, basic_anfa_matcher< basic_charset< wchar_t > > >, basic_anfa_matcher< basic_charset< wchar_t > > > regex; On "creators" and "create" functions. The name is somewhat misleading, since they fill target objects with compiled data rather than create them. Still, "charset compiler" sounds a bit weird... or does it? Anyway. The "creators" are subject to the following uses and requirements. They must be able to destruct themselves gracefully even if the expression they are being feeded with is only halfway done (in case someone has thrown an "unsupported" exception). The "create" function must do an implicit "pop" from the expression stack, so that the "creator" object could be reused. The "create" function can assume there's only one top-level expression tree node on the stack. -= Charset Issues =- (Should I rename them to "character sets" for consistency with the full-names style?) All the above templates have quite a freedom in intermixing different character types, let alone different character encodings. E.g., the sample program has all regex templates instantiated with wide characters, but the regex string itself is char-typed. This clearly needs to be controlled.

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