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Path: utzoo!watmath!watnot!watrose!jafischer
From: jafischer@watrose.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Megamax "bugs"
Message-ID: <8424@watrose.UUCP>
Date: Fri, 30-Jan-87 14:32:30 EST
Article-I.D.: watrose.8424
Posted: Fri Jan 30 14:32:30 1987
Date-Received: Sat, 31-Jan-87 04:47:27 EST
Reply-To: jafischer@watrose.UUCP (Jonathan Fischer)
Organization: U. of Waterloo, Ontario
Lines: 79


     >Grovel, grovel, abase, abase, repent...<
     *Ahem*   Referring  to  those  Megamax  "bugs"  I   mentioned 
previously:   I have  come up  with a  new  maxim, namely "A self-
taught programmer is a dangerous one."  Now I'm not exactly  self-
taught, but I am as far as C goes.  U of Waterloo doesn't teach  C
until some third year courses in which you're (naturally) expected
toi pick it up on your own.  I've even done about 5000 lines of  C
programming on  my work terms, but heck, after realizing that each
of the "bugs"  I mentioned were really quirks of the language that
I should be aware of, well... I'm more than a tad embarassed.  And
I deserve to be flame-broiled to death, since I really acted with-
out thinking  of the responsibility of  posting a supposed bug no-
tice to the Net, especially for such a popular product.

     The (++) problem:
     for (loop = 0;  loop <= whatever; 
          printf("%d %d\n", something[loop], other[loop++]))
          ;
     This will print out 'something[loop+1]' and 'other[loop]' 
on each line.  I.e.:
something[1] other[0]
something[2] other[1]
...
To me,  this looked like Megamax was doing something odd with  the 
(++) operation.  However, because of the order of arguments on the 
stack,  the third argument is being pushed on the stack before the 
second, and hence the '++' takes effect before the second argument 
is processed.   I just figured this out last night as I was  about 
to post  something saying  "look, here's   that compiler  error  I 
mentioned..."  I guess  this doesn't classify as a compiler error, 
does it?  It sure seems to be against intuitive reasoning, and the 
look and feel of the statement.  When looking at that statement, I 
assume, in my conditioned left-to-right way of looking at  things, 
that  the  argument  to the left should be  evaluated  before  the 
argument  to the right,  just like in an expression the terms  are 
normally  evaluated  left-to-right.   I'll have to watch  out  for 
this, since it will probably happen with any ST compiler.

     (My "C Programmer's Handbook" states that "the order in which 
the  argument  expressions  are  evaluated  is  not   [<--italics] 
guaranteed."  Oh.)

     The (%) problem:
     Nuts.   I can't  find it.   I  have a feeling that it  was an 
expression  something like  "Random()  % 8",  being  passed as  an 
int parameter,  and I should have typecast it into (int)Random() % 
8.  Something like that.

      Well.   I've  certainly learned my lesson.   I  should  have 
posted  the  original "bug notice" as a "Gee,  I'm  getting  these 
results with this and that C statement...  Is there something  I'm 
doing wrong?"  I guess I was too eager to be the hotshot who found 
some drastic bugs in Megamax...  *sigh*  I'm going to bed.  To all 
of the hundreds or thousands of people in front of whom I've  just 
humiliated myself: please accept my apologies.

     Just because I've made a fool of myself once,  though,  don't 
discount  my  previous  flame of Ms.EM.   I  even  downloaded  the 
MSPATCH.PRG that was posted to Compuserve.   No go.   I also tried 
everything with 'interrupts' on and off (it gives you that  option 
at  boot time),  and _nothing_ I tried (i.e.,  Lotus,  Dbase  III, 
Wordstar,  Norton  Utilities,  (even  CHKDSK.COM!),  and  a  dozen 
others) would run.  If we get the 5 1/4" drives in, I'll post some 
results.   Looks  like  we  have  to  wait  for  Atari's  hardware 
emulator.  Has _anyone_ out there had any  luck using DOS 3.2  and
the internal ST drives?  Is there _something_  else that  the user
must do before things will  run?  I've  always done it from a cold
boot,  so there weren't any strange accessories or TSR programs in
the way.  I tried the "flip keyboard" or whatever option.  It does
execute all the built-in DOS CLI commands, like 'dir' and 'cd' and
others.  But I simply could not get one single program to load and
run.

-- 
				- Jonathan Fischer 	(jafischer@watrose)
		or:   	watmath!watrose!jafischer
		or:   	jafischer%watrose@waterloo.csnet
		or:  	jafischer%watrose@waterloo.csnet@csnet-relay.arpa