C 03 equivalent for auto in the context of obtaining an allocator-CodePudding

auto source_allocator = source.get_allocator();

Is there a way of replacing auto in the above with something C 03/98-friendly, in the event where the type of allocator is not known in advance?

CodePudding user response：

Based on what you posted in the comments, it sounds like you're trying to do this inside a template.

Assuming you are expecting your templated type to be a std::container, or something compatible, you can do this: typename T::allocator_type in place of auto.

https://godbolt.org/z/Pda77vjox

CodePudding user response：

At least for standard containers, the container type is required to define container_type, so you'd normally end up with something on this general order:

template <class Container>
void foo(Container const &source) { 
    typename Container::allocator_type source_allocator = source.get_allocator();
    // ...
}

This is exactly the sort of situation for which they required standard containers to define those names. Of course, it also works fine with other containers that do the same.