Could you post an example? Is the concept check done in the return type
as with enable_if?
In C++11, we can use a default template parameter, rather than the return
type, which is what the `CONCEPT_REQUIRES_` uses. So for example, we can
write:
template())>
auto foo(T&&... xs)
{
...
}
This works as long as all the varidiac template types are to be deduced by
the
compiler. For classes this won't work:
// ERROR
template())>
struct foo
{
...
};
Because you can't have a default template parameter after the varidiac
template parameters in this context(you can when using speczializations).
Of course, you can't use `CONCEPT_REQUIRES_` for class specialization. In my
library, I do provide a `TICK_CLASS_REQUIRES` which can be used for class
specializations. Note that since it relies on `enable_if` it won't resolve
ambiguities like Concepts Lite will. For example:
template<typename T>
struct foo;
template<typename T>
struct foo())>
{
...
};
// Here we have to add a check for `RandomAccessIterator` to avoid
ambiguities
template<typename T>
struct foo() &&
!RandomAccessIterator<T>())>
{
...
};
Perhaps, there is a way to this using tag dispatching, I'm not sure.
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