That's rather like the use of "magic" return values in C, as in
while ((c = getchar()) != EOF)
putchar(c);
It's a handy shorthand, but it has the disadvantage of mixing result
types. Normally, c is a character, and sometimes it's a sentinel value
like EOF. To me, this is reasonably tolerable (though not ideal)
because EOF can be thought of a kind of pseudocharacter). Much worse,
though is
result = do_something_dangerous();
switch(result) {
case 0:
value = result;
break;
...
case 10:
fprintf(stderr, "Error number 10 occured!\n");
value = -1;
}
--- Aylesworth Marc A Ctr AFRL/IFSE <[EMAIL PROTECTED]> wrote:
> Could you also do this:
>
>
>
>
>
> MyFunct(a,b)
> new result
> if $get(a)="" set result=-1
> if $get(b)="" set result=-1
>
> set result=a*b
> ;//more code here.
>
> quit result
>
> one exit and result is always set.
>
>
> Thanks
>
> Marc Aylesworth
>
> C3I Associates
>
> AFRL/IFSE
>
> Joint Battlespace Infosphere Team
>
> 525 Brooks Rd
>
> Rome, NY 13441-4505
>
> Tel:315.330.2422
>
> Fax:315.330.7009
>
> Email: [EMAIL PROTECTED]
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of
> Chris
> Richardson
> Sent: Wednesday, September 14, 2005 9:42 PM
> To: hardhats-members@lists.sourceforge.net
> Subject: Re: [Hardhats-members] Re: More easy M syntax questions
>
> Kevin;
>
> I feel the same way about curley braces (in C and other legitimate
> languages). I find it so strange to see which closing brace goes
> with which
> opening brace.
>
> I have programmed in FORTRAN and APL before MUMPS and was very
> happy to
> NOT use the GOTO in MUMPS. Now the exit on condition can be
> abbomplished
> with a consistant set of exit actions by installing a dot block which
> allows
> for the negative/positive actions to decide an action and then to
> exit. It
> is what I call a herring bone filter. Here is a simplified form;
>
> EVALU8(A,B) ; Evaluate the string passed as A, contition returned in
> B
> N E,X
> S B=$G(B)
> S E=$G(A)
> S X="999;Unidentified Error: "_E
> D
> . I A?1.N S X="0;Numeric: "_E Q
> . I A?1.AN S X="0;AlphaNumeric: "_E Q
> . ; As many conditions as needed go here, but when the situation
> is
> found, exit the block.
> . ; Else was a precondition
> .QUIT
> S:'X B="Success"
> QUIT X
> ; ==============
>
>
>
>
>
> ----- Original Message -----
> From: "Kevin Toppenberg" <[EMAIL PROTECTED]>
> To: <hardhats-members@lists.sourceforge.net>
> Sent: Wednesday, September 14, 2005 5:17 PM
> Subject: [Hardhats-members] Re: More easy M syntax questions
>
>
> I have always been taught that goto's should be avoided like the
> plague. And that is the general rule I have always followed before
> working with M.
>
> One issue is that having to nest block of code with leader dots (e.g.
> . . . S I=1), makes it more awkard in my opion. So it becomes easier
> to have this:
>
> MyFunct(a,b)
> new result set result=-1
> if $get(a)="" goto FuncDone
> if $get(b)="" goto FuncDone
>
> set result=a*b
> ;//more code here.
>
> FuncDone
> quit result
>
>
> as compared to
>
> MyFunct(a,b)
> new result set result=-1
> if ($get(a)'="")&($get(b)="") do
> . set result=a*b
> . ;//more code here
>
> FuncDone
> quit result
>
>
> Another issue is that the for loops in M don't have a "break" or
> "continue" command, which makes the syntax a bit more awkward.
>
> Kevin
>
>
> On 9/14/05, Greg Woodhouse <[EMAIL PROTECTED]> wrote:
> > The reason I care is that I've been thinking about code analysis
> and
> > code generation lately. One topic of special inteest to me is
> > concurrent and distributed processing, and I've been thinking about
> > ways of effectively using multiprocessors to run sequential
> programs.
> >
> > --- Greg Woodhouse <[EMAIL PROTECTED]> wrote:
> >
> > > I was referring to the GOTOs as the "exits", not the QUIT.
> > >
> > > In another language, would your code have been something like
> this
> > >
> > > try
> > > Your code here
> > >
> > > except e1
> > > Handle exceptional condition 1
> > >
> > > ...
> > >
> > > except en
> > > Handle exceptional condition n
> > >
> > > finally
> > > "Cleanup" code goes here
> > >
> > > Normal exit here
> > >
> > >
> > > --- Kevin Toppenberg <[EMAIL PROTECTED]> wrote:
> > >
> > > > See below
> > > >
> > > > On 9/14/05, Greg Woodhouse <[EMAIL PROTECTED]>
> wrote:
> > >
> > > > >
> > > > > That's quite an interesting question. Is it better to have
> > > multiple
> > > > > exits or to have GOTOs that branch to a common exit point? It
> > > seems
> > > > > rather arcane, but two questions come to mind:
> > > > >
> > > > > 1. Is the single exit point used to ensure that all "cleanup"
> > > code
> > > > is
> > > > > in the same place?
> > > >
> > > > Yes. Also to make sure that my return values for the function
> are
> > > > properly
> > > > set etc.
> > > >
> > > > 2. Do you have multiple "normal" exits, or do the others
> correspond
> > > > to
> > > > > exceptional conditions?
> > > >
> > > > No, I only have one exit.
> > > > Thanks
> > > > Kevin
> > > >
> > > > --- Kevin Toppenberg <[EMAIL PROTECTED]> wrote:
> > > > >
> > > > > > Greg,
> > > > > > I use the GOTO because I always set things up such that
> every
> > > > > > function has
> > > > > > only ONE exit point. That way if I come back later, and I
> want
> > > to
> > > > do
> > > > > > something in the function before it exits, I can put the
> code
> > > at
> > > > the
> > > > > > end.
> > > > > > But if I have QUITS scattered about, then its more messy.
> > > > > > And no I haven't started abreviating code. I was just
> picking
> > > > > > through
> > > > > > existing code and trying to make it as easy for others when
> I
> > > > posted
> > > > > > here.
> > > > > > Thanks!
> > > > > > Kevin
> > > > > >
> > > > > > On 9/13/05, Greg Kreis <[EMAIL PROTECTED]> wrote:
> > > > > > >
> > > > > > > It quits the FOR loop. I believe the code is better
> written
> > > > with
> > > > > > the
> > > > > > > QUIT instead of the GOTO.
> > > > > > >
> > > > > > > S EX=0
> > > > > > > F D0=0:0 DO Q:EX
> > > > > > > . S D0=$O(^UTILITY(U,$J,DDF(1),D0))
> > > > > > > . S:D0="" D0=-1
> > > > > > > . I '$D(^UTILITY(U,$J,DDF(1),D0,0)) S EX=1 Q
> > > > > > > . S Z=^UTILITY(U,$J,DDF(1),D0,0)
> > > > > > > . D I^DITR
> > > > > > >
> > > > > > > BUT, BUT, BUT.... did you notice all the code that had to
> be
> > > > > > converted
> > > > > > > to full global references to be compliant with VA
> programming
> > > > > > standards
> > > > > > > on the use of naked references? (The rule in the SACC
> about
> > > no
> > > > line
> > > > > > > starting with a naked reference is a sound one, BTW, born
> of
> > > > > > > experience.) Also, you have to add a semaphore (EX in
> this
> > > > case) if
> > > > > > you
> > > > > > > want to avoid checking the global existence repeatedly.
> You
> > > can
> > > > see
> > > > > > > that by stretching the code out over several lines (what
> I
> > > > > > generally
> > > > > > > recommend) in this case made the code more verbose
> because we
> > > > now
> > > > > > have
> > > > > > > to manage what the context was handling when all on one
> line
> > > in
> > > > the
> > > > > > loop.
> > > > > > >
> > > > > > > Isn't it eye opening to see how many subtleties are in M
> > > code?
> > > > (I
> > > > > > am
> > > > > > > not sure why they wanted to set D0=-1 unless they were
> going
> > > to
> > > > > > > encounter problems with it being null beyond just the
> null
> > > > > > subscript
> > > > > > > error in the global reference that follows the check and
> set
> > > of
> > > > > > D0.)
> > > > > > >
> > > > > > > P.S.
> > > > > > > I notice you have taken to abbreviating commands... ;-)
> or
> > > are
> > > > you
> > > > > > just
> > > > > > > tearing apart something already written?
> > > > > > >
> > > > > > >
> > > > > > > Kevin Toppenberg wrote:
> > > > > > >
> > > > > > > >Hey all,
> > > > > > > >
> > > > > > > >I am working with this line of code:
> > > > > > > >
> > > > > > > >F D0=0:0 S D0=$O(^UTILITY(U,$J,DDF(1),D0)) S:D0=""
> > > > > > > >D0=-1 Q:'$D(^(D0,0)) S Z=^(0) D I^DITR
> > > > > > > >
> > > > > > > >
> > > > > > > >My question, does the QUIT in this line quit the For
> > > > > > > >loop, or quit the function?
> > > > > > > >
> > > > > > > >Would this be equivalent code:
> > > > > > > >
> > > > > > > >F D0=0:0 DO GOTO:'$D(^(D0,0)) LABEL1
> > > > > > > >. S D0=$O(^UTILITY(U,$J,DDF(1),D0))
> > > > > > > >. S:D0="" D0=-1
> > > > > > > >. Q:'$D(^(D0,0))
> > > > > > > >. S Z=^(0)
> > > > > > > >. D I^DITR
> > > > > > > >
> > > > > > > >LABEL1
> > > > > > > > QUIT
> > > > > > > >
> > > > > > > >
> > > > > > > >Thanks
> > > > > > > >Kevin
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >__________________________________
> > > > > > > >Do you Yahoo!?
> > > > > > > >Check out the new Yahoo! Front Page.
> > > > > > > >www.yahoo.com <http://www.yahoo.com>
> <http://www.yahoo.com>
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >-------------------------------------------------------
> > > > > > > >This SF.Net email is sponsored by:
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> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Greg Kreis http://www.PioneerDataSys.com
> > > > > > >
> > > > > > > "You are today where your thoughts have brought you, you
> will
> > > > > > > be tomorrow where your thoughts take you." (James Lane
> Allen)
> > > > > > >
> > > > > > >
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> > > > > > >
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> > > > >
> > > > >
> > > > >
> > > > > ===
> > > > > Gregory Woodhouse <[EMAIL PROTECTED]>
> > > > >
> > > > >
> > > > >
> > > > > "Without the requirement of mathematical aesthetics a great
> many
> > > > > discoveries would not have been made."
> > > > >
> > > > > -- Albert Einstein
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
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> > > > > https://lists.sourceforge.net/lists/listinfo/hardhats-members
> > > > >
> > > >
> > >
> > >
> > >
> > > ===
> > > Gregory Woodhouse <[EMAIL PROTECTED]>
> > >
> > >
> > >
> > > "Without the requirement of mathematical aesthetics a great many
> > > discoveries would not have been made."
> > >
> > > -- Albert Einstein
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > -------------------------------------------------------
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> >
> > ===
> > Gregory Woodhouse <[EMAIL PROTECTED]>
> >
> >
> >
> > "Without the requirement of mathematical aesthetics a great many
> discoveries
> > would not have been made."
> >
> > -- Albert Einstein
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > -------------------------------------------------------
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>
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===
Gregory Woodhouse <[EMAIL PROTECTED]>
"Without the requirement of mathematical aesthetics a great many discoveries
would not have been made."
-- Albert Einstein
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