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[Caml-list] Function forward declaration?
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Date: -- (:)
From: Issac Trotts <ijtrotts@u...>
Subject: Re: [Caml-list] Function forward declaration?
On Wed, Apr 07, 2004 at 03:15:19PM +0100, Richard Jones wrote:
> On Wed, Apr 07, 2004 at 11:52:17PM +1000, skaller wrote:
> > IMHO it isn't forward calling that is broken, 
> > but global variables.
> 
> A somewhat controversial viewpoint ...  While minimising the use of
> global variables might be a theoretical desirable goal, they are very
> useful when you're actually writing real programs under the schedule
> pressure for real users..
> 
> > > and this can be checked by the compiler.
> > 
> > How? *** 
> > 
> > What do you suggest if the compiler
> > is not sure if a variable is initialised or not?
> > Java bans, Felix allows, Ocaml forces the programmer
> > to hack.
> 
> The trouble seems to be that I have a perfectly practical and
> reasonable desire to see prototypes added to the language, because,
> believe it or now, it helps to solve some problems in the Real World.
> Now if there's some deep reason why it's actually impossible I would
> understand, but plenty of other languages (eg. C) seem to have
> prototypes and they get along just fine.

How about this:

# let f g x = g x  (* Pass the function g as an argument. *)
let g x = x*x      (* or whatever. *)
let f = f g        (* Define a fresh f in terms of g and the old f. *)
;;
val g : int -> int = <fun>
val f : int -> int = <fun>
# f 3;;
- : int = 9

> (Same, by the way, goes for a 'return' statement which OCaml is crying
> out for).

If you're looking for clarity, you can use the comment (* return *).  If
it's for flow control, you can raise an exception.

Issac Trotts

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