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boost/operators.hpp remarks
by Sylvain Pion 08 Mar '05

08 Mar '05

Hi, I have been using boost/operators.hpp recently, and found it quite good at removing lines of code from my maintainance area :) I have some remarks about it : 1/ The mixed operators are only provided if you know the type in advance and it is fixed. For example, it is not possible for example to mix with a template family of types. E.g. let's say that My_type has to provide mixed operators with all types X<U>. This is not possible to do with the current library. Another related thing is how to express "I want My_type to mix with all integral types". Maybe there could be a version of the operators that uses enable_if and tr1::is_integral somehow, for this purpose ? Just a thought. 2/ I think it is "Euclidean Ring", not "Euclidian Ring" ("e" instead of "i"), hence the names for euclidian_ring_operators<T> and similar, are unfortunate. -- Sylvain

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thread safety in boost date time
by Yitzhak Sapir 08 Mar '05

08 Mar '05

Boost date_time apparently has a thread safety problem in linux in that it calls localtime() in boost/date_time/time_clock.hpp and related functions rather than localtime_r() and related functions. This is even though BOOST_HAS_PTHREADS is defined by configure in user.hpp. Yitzhak Sapir

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casp.hpp workaround and more
by Gennadiy Rozental 07 Mar '05

07 Mar '05

1. Shouldn't this header use workaround from config/suffix.hpp instead of BOOST_EXPLICIT_DEFAULT_TARGET? 2. Shouldn't this header be split by ..._cast? 3. Doesn't numeric_cast facility shouldn't be deprecated? Genandiy

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RPC library
by Jarl Lindrud 07 Mar '05

07 Mar '05

Hi all, I've searched this list a bit and found a few mentions of rpc's (Remote Procedure Call), but nothing concrete. I've written a library for doing portable C++ RPC's, which can be downloaded at http://www.codeproject.com/threads/RMI_For_Cpp.asp Is there any interest in Boost for something like this, and if so in what directions do you all think it should be developed? Thanks! Jarl.

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Re: [boost] Re: Logo Contest Current Tally
by JOAQUIN LOPEZ MU?Z 07 Mar '05

07 Mar '05

----- Mensaje original ----- De: David Abrahams <dave(a)boost-consulting.com> [...] > Well, now Joel and Jeff Garland have both told me by private mail that > there doesn't seem to be anything wrong with having a discussion about > what's worth voting for, and I am basically convinced. I think > certainaspects of the logo are more important than others and > should be > considered. But before I start blurting out any specifics, let's hear > from the group. Is there any reason we shouldn't talk about how to > choose? We do almost everything at boost by public consensus. Why > not this time? Well, I don't have any strong opinion about whether this poll should be kept in privacy or not, but certainly there is a difference between the contest and other activities: the former is a voting process, unlike all other decisions taken here (including reviews.) Joaquín M López Muñoz Telefónica, Investigacion y Desarrollo

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Re: [boost] Re: Logo Contest Current Tally
by Iain Hanson 07 Mar '05

07 Mar '05

On Mon, 2005-03-07 at 12:48 -0500, David Abrahams wrote: > christopher diggins <cdiggins(a)videotron.ca> writes: > [snip] > Well, now Joel and Jeff Garland have both told me by private mail that > there doesn't seem to be anything wrong with having a discussion about > what's worth voting for, and I am basically convinced. I think certain > aspects of the logo are more important than others and should be > considered. But before I start blurting out any specifics, let's hear > from the group. Is there any reason we shouldn't talk about how to > choose? We do almost everything at boost by public consensus. Why > not this time? > I think it would be a good thing. If people are influenced by it will be no different than the review process. I also have no problem with the running tally. /ikh

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FSM Review
by Peter Petrov 07 Mar '05

07 Mar '05

I have used and watched closely this library for more than a year, since its early versions. Initially, we needed a good modern state machine framework for a project at the company I work for. After evaluating the possibilities, we decided to take the risk and go with Andreas' FSM, despite its early-alpha state at the time. Now, one year later, that choice has proved to be correct. We have used FSM in one more project and are planning to use it in future projects too. * What is your evaluation of the documentation? How easy (or hard) it is to understand library features? What can be improved? The documentation is very adequate. I was able to quickly understand how to use the basic features of the library, and then proceed to the advanced ones. At that time I had experience with different kinds of state machines, but primarily SDL-specified. FSM's documentation was my first introduction to UML state charts, and did the job well. The tutorial is excellent. The FAQ and Rationale sections give important answers to questions which are likely to arise. There is also an extensive Reference section, which I needed very rarely. * What is your evaluation of the design? What features are supported better by alternative FSMs? What could be added (or removed) from the library? To me, the design is good and follows naturally from the objectives of the library. It imposes some restrictions, although they can be overcome if necessary (for me it has not been necessary). For example, machines don't recognize polymorphic events, therefore they cannot "forward" unknown events to another machine. This can be circumvented by using a "wrapper" event around such events, which works, but only with asynchronous machines. Another example is the way that state machines are inherited - it's not very flexible and only allows altering how a state machine reacts to an already recognized event. One cannot add support for new events, except using again the "wrapper event" trick. * The library documentation contains few not yet solved issues (name, separating the library into two parts, exception handling). What is you opinion here? The name (boost::fsm, Boost.FSM) is fine for me. Regarding separating the library into two parts, I prefer it being separated, since the Worker part is useful by itself. * What is your evaluation of the implementation? Are there parts of code too obscure or duplicating exiting Boost functionality? Can something be factored out to standalone library or among general utilities? It's as obscure as its complexity requires. At the same time it is stable and bug-free, which is proved by extensive bulk-testing in our labs. * Are there performance bottlenecks? Does the library design fit requirements of real-time systems? How is it usable for embedded systems? Is the documentation clear on performance tradeoffs? The documentation is definitely clear on performance tradeoffs, and it's up to the potential user to take an informed decision. One tradeoff is that dispatch time is linear to the number of nested states. In my experience this is not a problem, since there are rarely more than two nested states, and I have never seen more than three. A possible problem is that states are constructed using operator new(). The documentation clearly states that, and the library allows overcoming the issue by specifying a custom allocator for the state machine, as well as writing custom operator new()'s for all state classes. I personally am against the second requirement and think that it complicates things too much. Specifying a custom allocator for the state machine should be enough. (this is mentioned in the documentation, in the Rationale section under "Memory management customization") * What is your evaluation of the potential usefulness of the library? Can you compare this FSM to other implementations? The greatest distinction of code written using the FSM library is its manageability. It's very easy to write and subsequently evolve state machines and most common mistakes are caught at compilation time. When state machines are involved, using FSM is definitely a great improvement over using a primitive framework, or not using a framework at all (the notorious switch/case idiom). Especially if the library's advanced features are used. * Did you try to use the library? With what compiler? Did you have any problems? Do you have tips for better support of older compilers? What are possible portability problems? Used with MSVC++ 7.1 and GCC 3.x. Currently without problems. In the early versions there were some minor issues which Andreas has addressed quickly. Regarding older compilers, I don't think they should be supported by this library. * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? In-depth study, as well as real-world usage. * Are you knowledgeable about the problem domain? To a good extent. I have developed two different state machine frameworks, although both of them were significantly lower level than FSM. I have also worked extensively with various kinds of state machines, mainly protocol-related and in telecom applications. * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Yes. Definitely.

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[interfaces] Hand written interfaces
by Jonathan Turkanis 07 Mar '05

07 Mar '05

Hi All, I'm working on ways to make the Boost Interfaces library easier to use. This involves making interface definitions compile faster and making them easier to read. Unfortunately, these are somewhat conflicting goals: really messy-looking interface definitions may compile much faster than simple ones. I'm working on four approaches to interface definitions; I plan to implement them all and then compare them. Right now I'm looking for feedback on number 4: 1. The current IDL, possibly slightly modified, in which an interface definition consists of a sequence of macro invocation 2. A modified IDL in which an interface definition consists of a single invocation; this increases the amount of preprocessor metaprogramming but decreases the amount of template metaprogramming 3. The pseudocode IDL, together with an IDL compiler which translates pseudocode definitions into C++ class definitions requiring virtually no metaprogramming. 4. Hand written interfaces, requiring virtually no metaprogramming. The point of allowing hand-written interfaces is to decrease compile times. There's no question that writing interfaces by handle will be the most difficult of the above four options. Still, writing interfaces by hand has to be reasonably straightforward or no one will ever do it. So here's my question. Consider the interface: interface IBar { void foo(const char*); int foo(int, int); }; Is the following definition of IBar so complex that it would be pointless to offer it as an alternative? template< typename Derived, typename Base, typename Flags > struct ibar_impl { struct type : Base { struct interface_metadata : metadata_base<Derived, Base, Flags> { const char* names = { "foo", "foo" }; typedef mpl::vector< void(const char*), int(int, int) > signatures; }; void foo(const char* name) { return invoker<interface_metadata, 1>::execute(this, name); } int foo(int n, int m) { return invoker<interface_metadata, 2>::execute(this, int, int); } }; }; typedef interface< ibar_impl<_, _, _> > IBar; Best Regards, Jonathan

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RE: [boost] Re: review of proposed fsm library
by Dave Gomboc 07 Mar '05

07 Mar '05

> > Otherwise you would be able to mix both synchronous and > asynchronous > > states in one machine, which doesn't make sense. > > While tangential to my original point about naturally > recursive structures, I'll take time out to disagree here > too. It _can_ make sense to combine async and sync behaviour > in different parts of a state machine when one is modeling > electrical circuits, e.g. in certain regions of the circuit > one may know that the behaviour is sync and not want to spend > extra CPU by going through all the async motions. I will quickly add that this issue (combining async and sync fsms) will occur whenever one has prior components that one wishes to assemble together, where some are async and some are sync. Dave

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Re: [boost] Re: review of proposed fsm library
by Dave Gomboc 07 Mar '05

07 Mar '05

> > The distinction made between state and state_machine, > which I > consider to be unfortunate, was not justified in > the rationale... > > There is at least one good reason - the library supports both > synchronous and asynchronous state machines, which are > essentially different beasts and are operated quite > differently. No such distinction exists for states, therefore > they shouldn't be treated the same way as state machines. However, asynchronous_state_machine is separated from both state_machine and state. Ergo, the reason must lie elsewhere. I didn't delve deeply into the library's support for asynchronicity, but I did consider it odd and amusing that at the level of hardware circuitry, asynchronous behaviour is the default, and work is done to get synchronous behaviour by adding latches and a clock, but that for fsm (and many, many other software components rather higher-level than a J-K flip-flop) the opposite was true. I do understand it, but I am not convinced that in this case it was the correct decision. Unforunately, I have to leave for work now. :-) > Otherwise you would be able to mix both synchronous and > asynchronous states in one machine, which doesn't make sense. While tangential to my original point about naturally recursive structures, I'll take time out to disagree here too. It _can_ make sense to combine async and sync behaviour in different parts of a state machine when one is modeling electrical circuits, e.g. in certain regions of the circuit one may know that the behaviour is sync and not want to spend extra CPU by going through all the async motions. Dave

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