>From: "Gennaro Prota" <[EMAIL PROTECTED]> > On Fri, 15 Nov 2002 16:05:05 -0500, David Abrahams > <[EMAIL PROTECTED]> wrote: > > >Douglas Gregor <[EMAIL PROTECTED]> writes: > >> You'll have to back that up with some standardese. AFAICT, 5.2.10/10 lets > >> addressof() work: > >> "That is, a reference cast reinterpret_cast<T&>(x) has the same effect as > >> the conversion *reinterpret_cast<T*>(&x) with the builtin & and * operators." > >> > >> (And that reinterpret casting T* -> U* -> T* preserves the original value). > > > >But you're not doing that. You're doing a reinterpret_cast T& -> U > >cv&, then taking the address, and reinterpret_casting to T*. Is that > >really covered by the standard? > > Who knows? When I encounter these sorts of situations I dream a > standard where propositions can be demonstrated like in mathematics or > counter-examples provided. Don't you?
You're not the only one. Bjarne Stroustrup says the same in "The Design and Evolution of C++" (p. 103): --- Start quote --- Tools for Language Design Theory and tools more advanced than a blackboard have not been given much space in the description of the design and evolution of C++. I tried to use YACC (an LALR(1) parser generator) for the grammar work, and was defeated by C's syntax. I looked at denotional semantics, but was again defeated by quirks in C. Ravi Sethi had looked into that problem and found that he couldn't express the C semantics that way. The main problem was the irregularity of C and a number of implementation-dependent and undefined aspects of a C implementation. Much later, the ANSI/ISO C++ committee had a stream of formal definition experts explain their techniques and tools and give their opinions of the extent to which a genuine formal approach to the definition of C++ would help us in the standards effort. I also looked at the formal specifications of ML and Modula-2 to see if a formal approach was likely to lead to a shorter and more elegant description than traditional English text would. I don't think that such a description of C++ would be less likely to be misinterpreted by implementers and expert users. My conclusion is that a formal definition of a language that is not designed together with a formal definition method is beyond the ability of all but a handful of experts in formal definition. This confirms my conclusion at the time. --- End quote --- Another comment, regarding using Spirit for parsing C++ that has been discussed here (D&E, p. 69): "To this day, Cfront has a YACC parser supplemented by much lexical trickery relying on recursive descent techniques. On the other hand, it _is_ possible to write an efficient and reasonably nice recursive descent parser for C++. Several modern C++ compilers use recursive descent." Regards, Terje _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
