Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!ubvax!lll-winken!uunet!mcvax!cernvax!ethz!heiser
From: heiser@ethz.UUCP (Gernot Heiser)
Newsgroups: comp.lang.modula2
Subject: Re: Termination of program
Message-ID: <493@ethz.UUCP>
Date: 3 Jul 88 17:14:07 GMT
References: <492@ethz.UUCP>
Reply-To: heiser@iis.UUCP (Gernot Heiser)
Organization: ETH Zuerich, Switzerland
Lines: 56

In article <492@ethz.UUCP> aplusl@ethz.UUCP (Albert Meier) writes:
}Although an IMPLEMENTATION MODULE makes provision for "hidden"
}initialisation code in Modula-2 programs, there is no simple
}standardised way of providing termination code.  In UCSD Pascal, 
}and in Pascal-Plus this could be done as follows
} 
} 
}         BEGIN  (*main code of unit, envelope or whatever*)
}           Initialise;
}           ***;
}           Terminate
}         END.
} 
}Here the *** essentially stands for "execute all the code of the 
}client".

This  corresponds  to the way  it is done in  SIMULA-67: a class initialization
part  may  contain an "INNER" statement; everything  after  the INNER statement
wasn't executed until later (`later' depending on the usage of the class).

}...
}One could not introduce exactly the same effect into Modula-2 
}without a syntactic change of a fairly radical nature.  However,
}one could achieve a useful compromise on the lines of the 
}following:
}...
}        IMPLEMENTATION MODULE Gizmo;
} 
}          IMPORT Somewhere;
} 
}          PROCEDURE CleanUp;
}            BEGIN
}              (* Termination code *)
}            END CleanUp;
} 
}          (* rest of module *)
} 
}          BEGIN (*Gizmo*)
}            Initialise;
}            Somewhere.TERMINATE(CleanUp)
}          END Gizmo.
} 
}...  One 
}important point is that the routines linked in this way should be 
}called (so far as possible) no matter how a program terminates.

Sorry,  I don't   see  that.  Why  should   the termination  part be  something
fundamentally   different from  the initialization part?    The latter is   not
executed  if some statement  in an  earlier initialized module's initialization
part causes program termination. In general, continuation makes  no sense after
a run time error, unless real exceptions are introduced  (which, in particular,
should allow the program to somehow determine the reason of the termination).
-- 
Gernot Heiser  Phone:       +41 1/256 23 48
Integrated Systems Laboratory   CSNET/ARPA:  heiser%ifi.ethz.ch@relay.cs.net
ETH Zuerich                     EARN/BITNET: GRIDFILE@CZHETH5A
CH-8092 Zuerich, Switzerland    EUNET/UUCP:  {uunet,mcvax,...}!iis!heiser