On Sunday, March 27, 2011 05:38:23 PM Lorenzo Caminiti wrote:
On Sun, Mar 27, 2011 at 10:04 AM, Thomas Heller <thom.heller@googlemail.com> wrote:
On Saturday, March 26, 2011 11:19:46 PM Lorenzo Caminiti wrote:
Hello all,
I am updating Boost.Local docs and I could use a some help in getting the Alternatives section right
http://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost_local...
I would really like to see the first row removed ... All alternatives you describe are using C++ syntax ... I know what you mean.
But
all the examples use regular C++ syntax.
I don't think think that Boost.Lambda and Boost.Phoenix use the usual C++ syntax to program the "function" body.
Usual is just a point of view.
If you suggest a text different than "Program body using C++ syntax" I am happy to consider changing the title of the row but I think the row itself should remain there.
This row indicates if the "function" body is programmed using the C++ syntax that programmers normally use to program C++ function bodies (and not other C++ constructs).
Well, still misleading. It doesn't make it invalid or "unusual" C++ syntax. We had this discussion before ... It is valid and legal C++. Both in syntax and semantic. The difference is that you need some extra function calls, pay attention to some oddities etc. with phoenix and lambda. But it stays valid C++ syntax.
This also has an effect on the type of compiler error messages that programmers will receive about their "function" body. For example, with Boost.Local programmers will receive the usual compiler error messages they receive when they miss-program a function body but with Boost.Lambda and Boost.Phoenix they will receive different compiler errors which they might be unfamiliar with.
Another thing what i really wonder is: You write that local classes can not be passed as a template parameter. I don't really get the difference between the local class and Boost.Local. What about this:
int main() { double sum = 0.0; int factor = 10;
struct add_impl { double & sum; int const& factor; add_impl(double sum, int factor) : sum(sum), factor(factor) {}
void operator()(double num) const { sum += factor * num; std::clog << "Summed: " << sum << std::endl; } };
boost::function<void(double)> add = add_impl(sum, factor);
Your example compiles on MSVC but it does not compile on GCC. As far as I understand it, this is not standard ISO C++ because you cannot pass the local class as a template parameter (in this case to boost::function).
$ g++ -Wall -Werror -I../../.. 01.cpp 01.cpp: In function ‘int main()’: 01.cpp:22: error: conversion from ‘main()::add_impl’ to non-scalar type ‘boost::function<void ()(double)>’ requested
Can your example be made to compile on GCC and standard ISO C++?
double nums[3] = {1, 2, 3}; std::for_each(nums, nums + 3, add);
(A semicolumn was missing at the end of the for_each.)
return 0; }
Doesn't seem to work ... anyway, what i wanted to know was how your implementation is different from that, I understand that the code is invalid cause function uses templates in the constructor ...
I would be happy if you sched some light on to why this isn't possible but why its possible with using your macros.
Boost.Local uses this trick to pass local functions as template parameters: http://lists.boost.org/Archives/boost/2010/09/170888.php You can see how this trick is actually implemented by the library macros at: http://svn.boost.org/svn/boost/sandbox/local/libs/local/doc/html/boost_local...
... doesn't really tell me anything, too verbose. And scattered with implementations details. A small English prose like text would help here ... probably. So it works because add has some pure virtual base class as static type! Aha ...
Thank you very much for your comments.
-- Lorenzo _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost