[config] Local classes as template parameters
On Sat, Feb 12, 2011 at 5:50 AM, John Bytheway <jbytheway+boost@gmail.com> wrote:
On 11/02/11 22:29, Lorenzo Caminiti wrote:
On Fri, Feb 11, 2011 at 4:31 PM, Lorenzo Caminiti <lorcaminiti@gmail.com> wrote:
From: John Bytheway <jbytheway+boost@gmail.com> 2. Might anyone care so much about performance that they absolutely must have the code inlined? The answer is probably "yes" (or at least there will be people who *think* they care, which is also a problem). For these people you could, if you choose, provide an alternate implementation which doesn't indirect through local::function<>, and thus will only work in C++0x (or C++03 with non-standard extensions).
Without inheriting from local::function_base<> and then using local::function_ref<> the local struct cannot be passed as a template parameter in C++. Is this different for C++0x (C++03)?
Yes, in C++0x local structs can be passed as template parameters. Obviously, in C++0x there are lambdas too, so you might think your library is useless, but I'd expect most compilers to support passing local structs as template parameters before they support lambdas, so there is some advantage in having this intermediate implementation. Also, your macros would allow writing code that worked in C++0x and C++03, with the virtual function business in only those compilers/modes where it is necessary.
Hello all, Is there a Boost.Config macro that indicates if the compiler allows local classes to be passed as template parameters? Thank you. -- Lorenzo
lcaminiti wrote:
Is there a Boost.Config macro that indicates if the compiler allows local classes to be passed as template parameters?
Does anyone know if there is such a macro in Boost.Config? For example, this config macro will tell if the following is allowed or not (supported by C++03 and later standards): int main() { struct { // Local class. void operator()(double x) { std::cout << x << std::endl; } } print; std::vector v(3); v[0] = 1.1; v[1] = 2.2; v[2] = 3.3; // The config macro will tell if compiler supports passing local object `print` as template param or not. std::for_each(v.begin(), v.end(), print); return 0; } Thanks a lot. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/config-Local-classes-as-template-paramete... Sent from the Boost - Dev mailing list archive at Nabble.com.
Is there a Boost.Config macro that indicates if the compiler allows local classes to be passed as template parameters?
Does anyone know if there is such a macro in Boost.Config?
I don't believe so, but note that we don't add new macros unless there is a clear need in a Boost library. HTH, John.
participants (3)
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John Maddock -
lcaminiti -
Lorenzo Caminiti