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From: adrian@ru-cs44.UUCP
Newsgroups: net.lang.mod2
Subject: Re: circular procedure types
Message-ID: <670@ru-cs44.UUCP>
Date: Sat, 19-May-84 06:49:21 EDT
Article-I.D.: ru-cs44.670
Posted: Sat May 19 06:49:21 1984
Date-Received: Mon, 14-May-84 01:09:31 EDT
References: <840@unm-cvax.UUCP>
Organization: Reading Univ. UK.
Lines: 33

Our compiler (M2UNIX for the PDP-11) doesn't allow this program,
complaining as follows:

    1 MODULE circproc;
    2 
    3 TYPE Circular = PROCEDURE(Circular, CARDINAL): CARDINAL;
 ****                                  ^74: type not declared
    4 
    5 PROCEDURE a(b: Circular;  x: CARDINAL): CARDINAL;
    6 BEGIN
    7     IF x = 0 THEN
    8         RETURN 1
    9     ELSE
   10         RETURN x * b(b, x - 1)
   11     END
   12 END a;
   13 
   14 PROCEDURE Factorial(n: CARDINAL): CARDINAL;
   15 BEGIN
   16     RETURN a(a, n)
 ****              ^128: type incompatibility
   17 END Factorial;
   18 
   19 END circproc.

I guess you could do it with two procedures and two definition modules
but ...

-- 
Adrian Pell		({vax135,mcvax,edcaad}!ukc!ru-cs44!adrian)
Computer Science Dept.
University of Reading
UK