Re: [Caml-list] C++ STL and template features compared with OCaml parametric polymorphism and OO features

[Brian Hurt <bhurt@spnz.org>]

On Mon, 27 Sep 2004, Jon Harrop wrote:

> I think we are, because I think iterators are only really useful in an 
> imperative setting. Hence C++ programmers use them extensively but OCaml 
> programmers do not. Folds are simply not feasible in C++. I'm sure Stepanov 
> would have reinvented them if they had been... ;-)

Two comments:

First, iterators are usefull in a functional setting, for two reasons.  
The first is they allow lazy application of transformations.  It's easy to 
define a map on an interator to do the transforms as the values get pulled 
out.  And second, they provide a generic way to plug data structures 
together.  All you need to write is a to_iterator and from_iterator for 
each data structure, and then all data structures can talk to each other.

Second, you can do fold, map, iter, etc. in C++- it's just a pain.  To 
emulate HOFs you define a new class with single virtual member function.  
The virtual member function then becomes your HOF.  Of course, 1 line of 
Ocaml code has just become a dozen lines of C++, but that doesn't mean it 
can't be done...

-- 
"Usenet is like a herd of performing elephants with diarrhea -- massive,
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                                - Gene Spafford 
Brian

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