Re: [Caml-list] [ANN] The Missing Library

[John Goerzen <jgoerzen@complete.org>]

On Thu, Apr 29, 2004 at 02:28:35AM +1000, skaller wrote:
> On Thu, 2004-04-29 at 01:18, John Goerzen wrote:
> > > In Ocaml you can add state of course. But it's a mess.
> > 
> > I don't find it all that problematic.  
> 
> Compare:
> 
> let count = ref 0 in
> List.iter
> (fun x -> 
>   if !start = 0 then 
>   (start := 1; print "["; print x; )
>   else (print ";"; print x)
> )
> lst; 
> if (!start <> 0) then print "]"
> 
> and please don't tell me that isn't a total mess compared with

Of course, your example ignores nicer features available for
this sort of thing.  For instance:

let print_list l =
  let printfunc count item =
    print_string (if count = 0 then "[" else ";");
    print_string item; count + 1 in
  if (List.fold_left printfunc 0 l) > 0 then print_string "]";;

Actually, I think that's more readable than your iterative example
below.

-- John

> proc print_list(){
>   read x;
>   if x == None goto empty;
>   print "["
> next:>
>   print x;
>   read x;
>   if x == None goto endoff;
>   print ";"; 
>   goto next:
> endoff:> 
>   print "]"
> empty:
> }
> 
> Notice there are NO FLAGS. The entire state
> is represented by the program counter.
> In a more complex problem, the entire
> state can be local. You can even write
> a recursive procedure .. that builds a list  ..
> or even a tree .. do you want modify 
> the external state like that, building
> a data structure to *emulate* a stack
> when you can actually have a real one?
> 
> By the way this is valid, executable Felix.
> And of course it works behind the scenes
> by emulating a stack :D
> 
> -- 
> John Skaller, mailto:skaller@users.sf.net
> voice: 061-2-9660-0850, 
> snail: PO BOX 401 Glebe NSW 2037 Australia
> Checkout the Felix programming language http://felix.sf.net
> 
> 
> 

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