On Thu, Apr 15, 2010 at 7:02 PM, Alexander Nasonov <alnsn@yandex.ru> wrote:
vicente.botet wrote:
VBE> Boost.ScopeExit showed a technique that can be used to emulate local functions. Alexander proposed long time ago to provide it independently from ScopeExit but to my knowledge this has not been done.
Sorry for the late reply, I'm not following every boost thread, I got this message via google alerts.
No problem: There is no rush and thanks a lot for your reply.
Yes, this has not been done. Local function can borrow argument binding syntax from ScopeExit but there are other things I need to think of. For instance, in
int BOOST_LOCAL_FUNCTION(f, (BOOST_LOCAL_FUNCTION_BIND( (a)(&b) ), int c)) { // ... } BOOST_LOCAL_FUNCTION_END
syntax, is there any way to shorten BOOST_LOCAL_FUNCTION_BIND to "bind"?
For using this in Boost.Contract I see the following issues: 1) The CONTRACT_BLOCK_INVARIANT() macro will have to take as parameters also `a`, `&b`, `int`, `c`, etc. This is as complex as requesting the user to program a separate (private) member const function with these const parameters and then call that function to check the block invariant condition in a constant-correct context: struct x { void f(int a) { int b = a; // CONTRACT_BLOCK_INVARIANT(a == b); // Don't use this because it is not const-correct. CONTRACT_BLOCK_INVARIANT(equal(a, b)); // Const-correct. ... } private: bool equal(const int& a, cont int& b) const { return a == b; } // Const-correct for a, b, and object this. }; 2) How do I make the object (this) available within the local function? I could pass it as a 'self' parameter but then the assertion code will have to say, for example, `self.size()` instead of just `size()` and that is less readable...
The syntax doesn't have to be exactly as above. If someone could take a lead on this it would be great. I don't have time for this, I'm afraid.
I will experiment with this a bit more. If I can use BOOST_LOCAL_FUNCTION_... for CONTRACT_BLOCK_INVARIANT() (resolving issues 1) and 2) above) then I am happy to take the lead in separating this functionality from Boost.ScopeExit as part of Boost.Contract development. -- Lorenzo