Are there cases where a typedef is absolutely necessary?

Question

Consider the following excerpt from the safe bool idiom:

typedef void (Testable::*bool_type)() const;
operator bool_type() const;

Is it possibl

Answer 1

My analysis says that it is not possible without using typedef. The compiler sees ( as the first token and assumes you are overloading () operator, which shouldn't have any arguments (The arguments would come in next set of parenthesis). Putting any set of extra parenthesis wouldn't help either - but would actually confuse the compiler and hence set of more errors.

Most of the STL code is on top of typedefinitions, and we should/must use them!