RE: Imperative programming in Caml

[Don Syme <dsyme@microsoft.com>]

I don't know how it fits with the grammar, but something like
  mutable finished = false 
  mutable list = Empty
  mutable here = list 

might make things a bit clearer.  You could have implicit dereferencing for
everything declared with "mutable" and something like C's "&finished" if you
wanted to pass the reference.

Just a thought,
Don



-----Original Message-----
From: Walid Taha [mailto:taha@cs.chalmers.se]
Sent: 03 August 2000 20:20
To: caml-list@inria.fr
Subject: Imperative programming in Caml



[Apologies in advance for purists that this project might offend.]

Dear all,

Below is one of my first attempts at imperative programming in ML: a
program that reads a list of numbers and squares them, using a "mutable
list".  The presence of a "while" construct and easy of terminal IO in
Caml should help an imperative programmer feel at home.  But I am
concerned (and a bit surprised, actually) that the use of "let" bindings
and the presence of normal variables in addition to "mutable" variables
might make it more difficult to explain this program to a beginer that is
*not* interested in the functional aspects.  If any one has suggestions
for making this program more "imperative", I would appreciate it.

Many thanks in advance,

Walid.

---

let squareMany () =
 print_string "\nPlease enter zero (0) to stop.\n\n"; 
 let finished = ref false 
 and list = ref Empty in 
 let here = ref list in
 while not(!finished) do
        print_string "Enter a number : ";
        let number = read_int () in
        if number<>0 
         then begin
               let new = ref Empty in
               !here := Cell (number, new);
               here := new;
              end
         else begin
               finished:=true;
              end 
       done;
 print_string "Here are the squares of the numbers you entered: ";
 while (!list)<>Empty do
       let (Cell(number, rest)) = !list in
           print_int (number*number);
           list := !rest;
           print_string " ";
       done;
 print_string "\n\nGood bye!\n\n";;