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library-based property implementation
by Reece Dunn 08 Nov '04

08 Nov '04

Hi All, I have been working on an implementation of a library that allows you to define properties, based on the wg21 N1615 paper by Lois Goldthwaite. The code is committed to the sandbox (under the property directory) with tests and preliminary documentation. I have seperated the properties into two. The boilerplate code for operator overloads, organised by rank, where rank is the number of indices (the term is borrowed from Tensor algebra) provides one group. The other group is the property storage that implements the get and set functions that the boilerplate classes use to implement the operator overloads. : Scalar Properties A scalar property is a single-element property. You can have simple properties that either store their values internally or reference an external data member: class object { int val; public: scalar_property< aliased_property< int > > Val; object(): Val( val ){} }; int main() { scalar_property< value_property< int > > ival( 0 ); ival = 7; ival += 3; int j; scalar_property< aliased_property< int > > jval( j ); jval = 2; assert( j == 2 ); } You can also define more complex properties that use class methods to control them: class object { int val; public: int get_Val() const{ return val; } void set_Val( const int & v ){ val = v; } scalar_property< object_property < int, object, &object::get_Val, &object::set_Val > > Val; object(): Val( this ){} }; : Rank 1 Properties A rank 1 property is a 1-dimensional property. For example: class result_set { public: // property record index[]; record get_record( int i ) const; void set_record( int i, record r ); boost::rank1_property< boost::rank1_object_property < record, int, result_set, &result_set::get_record, &result_set::set_record > > record; public: result_set(): record( this ) { } }; Regards, Reece

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[1.32] [function] documentation missing
by Caleb Epstein 08 Nov '04

08 Nov '04

In the release candidate tarballs, the documentation for the "function" library is redirecting to http://www.boost.org/regression-logs/cs-win32_metacomm/doc/html/function.ht… It looks like the Boost.Book documentation isn't being generated for this library. Is this expected? -- Caleb Epstein caleb.epstein(a)gmail.com

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Re: [boost] GUI Library Proposal for a Proposal
by George van den Driessche 08 Nov '04

08 Nov '04

> Message: 2 > Date: Mon, 08 Nov 2004 10:42:21 -0500 > From: Beman Dawes <bdawes(a)acm.org> > Subject: Re: [boost] GUI Library Proposal for a Proposal) > To: boost(a)lists.boost.org, boost(a)lists.boost.org > Message-ID: <6.0.3.0.2.20041108102747.0272bec0(a)mailhost.esva.net> > Content-Type: text/plain; charset="us-ascii"; format=flowed > > At 07:38 PM 11/7/2004, George van den Driessche wrote: [snip] > >So what do you stand to gain, other than being able to write GUIs in > >your favourite language, as opposed to your second-favourite language? > >The only thing I can think of is that you don't have to worry about any > >bridge between languages. > > What you say makes a lot of sense if just you is involved. Or perhaps a > small enough group that they can all agree on the second-favorite language. > > But in larger organizations that approach results in a proliferation of > languages. I know of a company that has let programmers write code in any > language they like. The result is a nightmare. Over a dozen languages are > in common use. The toolchains on some projects are so convoluted that the > projects cannot be moved between the several operating systems in use at > the company. Programmers cannot freely move to another project because they > often don't know all the languages that are required. It is a serious mess. > > Thus the use of C++ as a GUI language may be sub-optimal as far as the > small picture goes, but could be a really smart move in terms of the big > picture. That's a convincing point. I'm glad it's a convincing point, because I like C++ :) Only, sometimes I wonder whether we're all so obsessed with the language that we can't stand back and realise that some other language is appropriate for a given task. Makes me think: if there was some language that easily spanned the range from static to dynamic code, then everyone could learn that and that only. Never mind... > Because what we are talking about is a library, rather than something in > the core language, non-users of the library don't pay for something they > don't use. As long as a C++ GUI library is useful to a significant number > of people it doesn't matter if lots of others choose a dual language > approach. True. Personally, I quite like the thinking behind Win32GUI, and I've been wondering about the viability of porting it to run on top of Carbon on OSX. I just needed a bit of persuasion that it's worth pursuing at all. I'm not sure how far the event handling systems can be aligned, but I'm certainly going to look into it. If it works, it'll need a different name :) George

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const_string + recursive_variant = boom
by Caleb Epstein 08 Nov '04

08 Nov '04

I've been trying to build a generic "message" type class using boost.variant and have just run across a problem when trying to convert it from using std::string to using the proposed boost::const_string. Attached is a small test case and the output from gcc 3.3.2 (the latter gzipped due to its hugeness). All is well if the mystring type is std::string. Any thoughts on how to fix this? -- Caleb Epstein caleb.epstein(a)gmail.com

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[FSM] Patches for gcc-3.4.1
by Jürgen Hunold 08 Nov '04

08 Nov '04

Hi ! The attached patch makes the FSM-examples (except PingPong) compile with gcc-3.4.1 These are mostly scoping issues. Tested against gcc-3.3.x. Any one interested in BB.V2 Jamfiles for FSM ? Yours, Jürgen -- * Dipl.-Math. Jürgen Hunold ! Institut für Verkehrswesen, Eisenbahnbau * voice: ++49 511 762-2529 ! und -betrieb, Universität Hannover * fax : ++49 511 762-3001 ! Appelstrasse 9a, D-30167 Hannover * hunold(a)ive.uni-hannover.de ! www.ive.uni-hannover.de

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Shortcut regex notation
by Schalk_Cronje＠McAfee.com 08 Nov '04

08 Nov '04

Would anyone be interested in having a perl-like regex shortcut notation? The original idea was born during a local C++ focus group discussion. Looking further into the feasibility I thought that this might be a useful addition to Boost. Possibly something like the following (from some proof-of-concept code) using namespace boost::short_regex; std::string str("And he said: 'BLAH BLAH'"); // [1] Substitutes first occurrence and copy (calls boost::regex_replace) // perl: ($s2=$str) =~ s/(BLAH)/Hooray/; std::string s2= _s / "(BLAH)" / "Hooray" / str; // [2] Substitute globally and copy // perl: ($s2=$str) =~ s/(BLAH)/Hooray/g; s2= _s / "(BLAH)" / "Hooray" / _g / str; // [3] Substitute first occurrence in-place // perl: $str=~ s/(BLAH)/Hooray/; ~_s/ "(BLAH)" / "Hooray" / str; In the above _s and _g are special placeholder/tag objects sort of like _1,_2. Other could include _i (case-insensitive), _m (string as multiple lines) and _s (string as single line). Multiple modifiers can be added using (,) // [4] Substitute globally and copy // perl: ($s2=$str) =~ s/(BLAH)/Hooray/gi; s2= _s / "(BLAH)" / "Hooray" / (_g,_i) / str; The purpose will not be to shortcut all of the boost.regex functionality, just the common cases, as in perl or sed. Cases [1] and [3] is very close to the perl and would be easy to understand, however [2] and [4] is moving away from perl-syntax. This might be considered illegible by some.

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Re: Points vs Vectors / GUI Library Proposal for a Proposal)
by George van den Driessche 08 Nov '04

08 Nov '04

Noah Stein wrote: > >> This makes them almost the same thing. You can treat vector as a >> point, and point as a vector. Besides, we are talking about R^2, >> which is a vector space. > > Sure, there's an isomorphism between points and vectors; however, that > doesn't make them the same. There's an isomorphism between the > functions > f(x)=x and f(x)=2x; however, that does not make those two equations the > same. This could be explained by analogy with C++, which more readers here might be familiar with: the difference between points and vectors is the same as the difference between C++ pointers and C++ ints. You can add a pointer to an int, or an int to a pointer, but you can't add two pointers. However, you can subtract two pointers to get an int. Likewise, it's not really meaningful to talk about the sum of two positions, but the difference between them is the vector from one to the other. Back on the subject of a GUI library: I understand the motivation - that's where wxWindows arose. And I realise that nowadays a GUI library could be done in a much more modern C++ style. But my question is: is C++ the right language? I don't want this to descend into a religious war - C++ is my favourite language, but it isn't the best language for every task. Would a higher-level, more dynamic language be more suitable for GUI work? In a perfect world, I'd do all my back-end stuff in C++ and all the front-end development in, say, Python. By doing all the GUI work in C++ instead of an interpreted language, you: a) spend a lot more time recompiling. b) can less easily tweak a running program to try out different ideas. c) have to spend a lot of effort to construct a domain-specific language (c.f Spirit; see (a)). d) probably end up with a bigger codebase. So what do you stand to gain, other than being able to write GUIs in your favourite language, as opposed to your second-favourite language? The only thing I can think of is that you don't have to worry about any bridge between languages. George

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OOPSLA Workshop...
by Tommy 08 Nov '04

08 Nov '04

Hi, a couple of months ago, I noticed an announcement in this list for Boost’s Oopsla Workshop. The topics and goals of that workshop (review position papers / libraries, discuss new library proposals, their relative merits, benefits and weaknesses, and provide feedback on initial designs) looked very interesting. So, after that event took place (Oct 25), I’ve looked out for material describing the results of that workshop - but I have not been able to find anything!? Has the results of the workshop been put together? If so, is the outcome publically available somewhere? Regards, Curious Tommy

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boost::ref simple question
by Neal D. Becker 08 Nov '04

08 Nov '04

This must be a common question. I want to use std::transform with a function object that is expensive to copy, so I want to pass by reference. I tried to use boost::ref for this, but this simple test doesn't work: struct Op { int operator() (int x) { return 1 + x;} Op() {} private: Op (const Op&); }; int main() { vector<int> x (4); vector<int> y (4); Op o; std::transform (x.begin(), x.end(), y.begin(), boost::ref(o)); } Any suggestion?

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[regex] any interest in finite automata-based regex engine?
by Vladimir Pozdyayev 08 Nov '04

08 Nov '04

Hello. Are there any plans to add finite automata-based subengine to the regex library? If there are, I can submit the algorithm/implementation of a modified nondeterministic FA which takes care of * greedy and lazy quantifiers, * eagerness of the alternation operator, * non-longest matches (`best' in the Perl-ish sense with respect to greediness/laziness/eagerness), * substring capturing. All these features being included, the time cost of a match is O(N(E+C)L), where N is the number of states, E is the average epsilon-closure size per state, C is the number of capturing parentheses, and L is the input length. As far as I know that's the lowest order of time complexity in this area (corrections are welcome)---though, of course, deterministic FA would be even faster. I suppose there's no point in adding another regex library, but being able to guarantee linear time cost in an existing one would be nice. -- Best regards, Vladimir Pozdyayev.

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