From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.8 required=5.0 tests=BAYES_00,INVALID_DATE
	autolearn=no autolearn_force=no version=3.4.4
Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!philabs!cmcl2!seismo!think!nike!cad!ucbvax!vrdxhq.UUCP!drm1
From: drm1@vrdxhq.UUCP (Donn Milton)
Newsgroups: net.lang.ada
Subject: Re: Procedure Parameters in Ada
Message-ID: <8606111601.AA26619@vrdxhq.uucp>
Date: Wed, 11-Jun-86 12:01:29 EDT
Article-I.D.: vrdxhq.8606111601.AA26619
Posted: Wed Jun 11 12:01:29 1986
Date-Received: Sat, 14-Jun-86 06:38:23 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
List-Id: <comp.lang.ada>

With reference to Chris Henrich's comments on type-checking in Pascal,
the Pascals I've seen only require that the type of the return
value be specified, such as:
		procedure dummy (function f: real);
There is no way to specify what the parameters to the formal function
'f' must be.  Thus although some type checking is possible, it is
IN GENERAL not possible to check that calls of f will always use the
correct parameters.  Recursive calls to a type-checking routine
won't hack it.

Please note:  the validity of the last sentence in the above paragraph
is by no means immediately obvious (at least to me).  One might
imagine the possibility of a type-checker that took into account
all possible execution paths of a program in order to check that all
procedures are always called with the correct number and type of
parameters.  But Langmaack, with a rather ingenious argument, shows
that such a type-checker cannot in fact be built (in the absence of
fully-specified procedure parameter types).

Donn Milton