STL, Ada, C++ (Was Re: The Next Microsoft?)

[Brian Rogoff <bpr@shell5.ba.best.com>]

On Fri, 5 May 2000, Bill Greene wrote:
> Hyman Rosen wrote:
> > 
> > ...
> > Ada has nothing like it [STL], since it is missing automatic instantiation
> > of generics.
> 
> Ada must have something like it, since Stepanov ported STL from Ada to
> C++.

There are Ada versions of STL-like libraries, where "-like" means that
the libraries are based on active iterators defined over sequential 
containers with algorithms parameterized in terms of those iterators, and
hence independent of the particular type of container. It happens that
operations of C pointer arithmetic and random access map well to the 
traversal of sequential data structures and so you get a nice syntactic 
dovetailing in the C++ STL with this part of generic programming. Clearly  
non-sequential collections can't be handled this way. I don't think Ada's 
functional syntax for ++, --, etc is a fundamental problem.

I agree that the lack of automatic instantiation is a weakness of Ada
generics vis-a-vis C++ templates. There are other places where that 
facility would come in handy besides STL style generic programming. I 
don't think their absence is fundamental, but I suppose that is debatable. 

Ada has subprogram nesting and allows you to instantiate generics with 
local functions and overloading on return type. So generic programming is 
different in Ada, less powerful in some ways, due to the lack of automatic
instantiation, more powerful in others. 

I think that the STL is well designed, and has certainly influenced the 
design of C++ in a good way. If anything, I wish templates and the STL had 
been in the language earlier, and the OO part had come later. 

-- Brian