In this exercise, you will be implementing std::any by removing functionality
from std::function.
Open this wandbox
(b,
b,
b,
b,
b,
b).
The header file "function.h" contains a fundamentally complete implementation of
std::function (but without the Small Object Optimization).
This wandbox also contains a header file named "any.h" that is simply a copy of "function.h".
1. Read "function.h" from top to bottom. Does it make sense? Can you match up the class definitions in the actual code with the pieces of the diagram from today's slide presentation?
2. Modify "any.h" so that it is a valid implementation of std::any.
You can try to do it on your own, or you can follow this checklist.
The necessary changes are:
Signature. class any is
a concrete class, not a template.nullptr_t and
is_specialization_of_function_v.operator().operator bool.target_type() to type().function to any.
3. (Optional) Notice that we left any::target() as a public member function,
whereas in the actual standard library there is no such function (just any_cast).
Make any::target() a private member function and make any_cast a friend
of any.
In your opinion, which interface seems "better": private-member-function-and-friend,
or public-member-function? Why?
You're done with the third set of exercises! Sit back and relax, or optionally, browse the following blog posts.