Why is allocator::rebind necessary when we have template template parameters?

Question

Every allocator class must have an interface similar to the following:

template
class allocator
{
    ...
    template
    s         


        

Answer 1

A quoted text from Foundations of Algorithms in C++11, Volume 1, chap 4, p. 35 :

template  
struct allocator 
{  
   template   
   using  rebind = allocator; 
}; 

sample usage :

allocator::rebind x;

---

In The C++ Programming Language, 4th edition, section 34.4.1, p. 998, commenting the 'classical' rebind member in default allocator class :

template
     struct rebind { using other = allocator;};

Bjarne Stroustrup writes this:

The curious rebind template is an archaic alias. It should have been:

template
using other = allocator;

However, allocator was defined before such aliases were supported by C++.