Article View: comp.lang.modula2
Article #969Re: JPI M2 2.00 - PROCEDURE FUNCTIONS & ERROR CHECKING
From: Jens Tingleff
Date: Tue, 24 Jul 1990 10:43
Date: Tue, 24 Jul 1990 10:43
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2209 bytes
dhinds@portia.Stanford.EDU (David Hinds) writes:
>In article <90204.213559TRL3@psuvm.psu.edu> TRL3@psuvm.psu.edu (Tim Larson) writes:
>>In article <1960.26A95065@puddle.fidonet.org>,
[..]
>>
> I would be very surprised to see a compiler that flagged the above
>routine as an error. I don't think that leaving the possibility of
[..]
Quite right, a warning is perhaps appropriate.
>the problem is insurmountable. A compiler could require that all execution
>paths end in RETURN statements, but that is still a non-trivial extension
>to the language syntax.
As well as a VERY pointless one, isn't the general case the
Halting Problem ??
Anyway, in a lot of code the programmer *knows* that a RETURN will be
encountered. Even if checks are done manually, that may not result
in a RETURN, e.g.
PROCEDURE FunnyStuff(arg1 : INTEGER) : BOOLEAN;
BEGIN
IF arg1 < 126 THEN (* Cath errors. *)
InOut.WriteString("ERROR : plane just crashed, tough luck. Bye");
InOut.WriteLn;
HALT
END;
CASE arg1 OF (* So this is stupid, so what ? *)
127 : RETURN TRUE
| 128 : RETURN FALSE
END;
END FunnyStuff;
Even if M-2 *does* provoke the programmer to reflect on the programming,
there is no reason for a straight-jacket requirement of a RETURN statement
that's always reached.. .
Jens
Jens Tingleff MSc EE, Institute of Computer Science, Copenhagen University
Snail mail: DIKU Universitetsparken 1 DK2100 KBH O
"It never runs around here; it just comes crashing down"
apologies to Dire Straits
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!dkuug!freja.diku.dk!skinfaxe.diku.dk!jensting From: jensting@skinfaxe.diku.dk (Jens Tingleff) Newsgroups: comp.lang.modula2 Subject: Re: JPI M2 2.00 - PROCEDURE FUNCTIONS & ERROR CHECKING Message-ID: <1990Jul24.104303.4787@diku.dk> Date: 24 Jul 90 10:43:03 GMT References: <1960.26A95065@puddle.fidonet.org> <90204.213559TRL3@psuvm.psu.edu> <1990Jul24.060519.23417@portia.Stanford.EDU> Sender: news@diku.dk (The Netnews System) Organization: Department Of Computer Science, University Of Copenhagen Lines: 45