Le 13/01/13 13:30, TONGARI a écrit :
Hi all,
One of the few things I appreciate in Java is the labeled-break feature. I think C++ would provide it as well in future standard but it seems that there's no even such a proposal.
In lack of the language feature, a simple emulation can be used:
--------------------------------------------------- #define BOOST_SCOPE(name) \ if (const bool LABELED_SCOPE_##name = false){break(name); name:;} else
#define break(name) \ (void)LABELED_SCOPE_##name; goto name; --------------------------------------------------- Now we can write:
BOOST_SCOPE(a) { break(a); cout << "123\n"; }
The real world usage would reside in nested loop&switch where labeled-break really shines.
Thoughts? Sorry if this idea is too simple and somewhat rejected before...
Beta language provides restart and leave a named blocks which are a little bit more structured than gotos. L:: { restart L; leave L; } which in C/C++ could be implemented as restart_L: { //restart L; goto restart_L; //leave L; goto leave_L; } leave_L; Maybe adapting your macros both can be provided #define BOOST_RESTART(name) \ goto BOOST_NAMED_BLOCK_RESTART_##name #define BOOST_LEAVE(name) \ goto BOOST_NAMED_BLOCK_LEAVE_##name #define BOOST_NAMED_BLOCK(name) \ BOOST_NAMED_BLOCK_RESTART_##name: \ if (const bool BOOST_NAMED_BLOCK_##name = false){ (void)BOOST_NAMED_BLOCK_##name; BOOST_NAMED_BLOCK_LEAVE_##name:;} else With these macros we can be able to do the following BOOST_NAMED_BLOCK(L) { BOOST_RESTART(L); BOOST_LEAVE(L); } The problem is that BOOST_NAMED_BLOCK(L) is not an statement but two. Maybe you see a way to workaround this limitation. I don't know however if the name LEAVE is a better name on the c++ context. Best, Vicente