Subj : Re: OO compilers and efficiency
To   : comp.programming
From : Jon Harrop
Date : Wed Jul 27 2005 11:43 am

Chris Dollin wrote:
> Jon Harrop wrote:
> > Why do you say "limited" update?
>
> In ML you can update only array elements and the contents of Ref
> cells, if I remember correctly. In Scheme, it appears to be part
> of the culture rather than the language, but I could easily be
> out-of-date.
>
> As opposed to languages where, generally speaking, variables are
> expected to, well, vary, unless you take syntactic steps - `const`,
> `final` - to say otherwise.

Right, so there is an equivalence:

C     <->  ML
int        int ref
const int  int

My objection was only that I wouldn't have called the ML side "limited"
because it can do everything that the C side can.

In OCaml (probably SML too) you can also update record fields which have
been marked "mutable". In fact, a "ref" is nothing more than a record with
a single mutable field:

  type 'a ref = { mutable contents: 'a }

-- 
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com

.