Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!tuvie!brock
From: brock@tuvie (Inst.f.Prakt.Info 1802)
Newsgroups: comp.lang.modula2
Subject: Are procedure types breaking modules?
Keywords: procedure types, modules
Message-ID: <688@tuvie>
Date: 22 Apr 89 16:48:22 GMT
Reply-To: ulrich@vip.UUCP (Ulrich Neumerkel)
Organization: Technical University of Vienna, EDP-Center
Lines: 19

When considering 6.8 of the Modula-2 report only procedures local to
other procedures and standard procedures are forbidden to be assigned
to a variable of a procedure type. This means that it is possible
to call a procedure which is not exported from another module, when
you pass the procedure dynamically. I do not believe that this
feature is really undesirable, however was it really intended?
The problem that might arise here is that there might be
introduced invisible dependencies. The alternative would be a complicated 
dataflow analysis or even a runtime check. 

o	Is this a desirable feature, have you used it in "real" programs?
o	Are there any alternatives to it?

Just to cite Wirth (3rd ed. p84) [...checking no absoulte safeguard...]
>After all, it [module concept] concerns formal, syntactic aspects only; it 
>does not cover the semantics. <Well, we are here on the razors egde...>

Ulrich
(ulrich@vip.at UUCP: ...!mcvax!tuvie!vip!ulrich)