🚀 go-pugleaf

Berkeley Pascal does not have an otherwise clause, so Ultrix
Berkeley Pascal probably doesn't either.  They won't unless
you can convince someone to put in the ~20 line source code
change to do it. . . .

(I put it in here for a while for TeX, but now we have Pastel,
so who needs pc?)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland

> I am trying to convert an existing Pascal program to run under Ultrix, 
> on a VAX, but do not have access to the internal documents for this
> implementation.  The program makes extensive use of an "otherwise" clause
> in its "case" statements.  I have blindly tried all variations I have seen
> in other Pascal implementations, without success.  
> 
> Can anybody out there tell me whether there is, in fact, an extension for
> a "none of the above" case, or that such an extension does not exist?
> 
> -- 
> Ben Cranston  ...{seismo!umcp-cs,ihnp4!rlgvax}!cvl!umd5!zben  zben@umd2.ARPA

Berkeley added a -O option to pxp sometime during 4.2.  If you do
	pxp -O prog.p > newprog.p
then prog.p can have a case labelled "others:", and pxp -O will create
a newprog.c where such case statements are changed to:
	if <case expr> in [<list of non-"others:" labels in case>] then
		case <case expr> of
			<non-"others:" cases>
		end
	else
		<statement for "others:" case>

If the range of the <case expr> isn't too big, the code generated is
a bit-vector membership test, which isn't too bad.  However, I
recently reduced the running time of a program by a factor of 8 by
noticing that large set membership tests get translated into a
push of all the members onto the stack, followed by a call to
a procedure to check each.  (The fix was to change that code manaully,
with a more efficient range test for the "others:" cases.)
So be warned.

When I and others ported TeX to UNIX, the "others:" problem had to be
solved.  We looked at pc's source, and found it was quite easy to add
an "others:" clause capability.  The compiler already generates code
to check for "none of the cases", since it has to produce a runtime
error for that.  We asked Berkeley if they would consider putting
the fix into pc, and they said no, because they didn't want to add
such a non-standard feature to the language (and also because more
programs than just pc would have to change to support a new language
feature).  Instead, they came up with the pxp -O solution, which
is the one used in TeX right now.  I don't think the large range
problem shows up there.

Sorry, but I don't have the changes to pc to add "others:" anymore.

			Howard Trickey
			...decwrl!Glacier!Shasta!trickey

Although the Berkeley Pascal compilers don't support the "others"
clause (or whatever it is called; run strings on pxp and see if
something pops up) pxp has a hack in it that will do what you want.
Just give pxp the -O flag and it will turn case statements that use
"others" into the appropriate

	if foo in [...] then
		case foo of
		...
	else
		...

Just do something like

	pxp -O myfile.p > mynewfile.p
-- 
	rusty c. wright
	{ucbvax,ihnp4,akgua,hplabs,sdcsvax}!sdcarl!rusty

In article <6830@Shasta.ARPA> trickey@Shasta.ARPA writes:
>When I and others ported TeX to UNIX, the "others:" problem had to be
>solved.  
>                 We asked Berkeley if they would consider putting
>the fix into pc, and they said no, because they didn't want to add
>such a non-standard feature to the language 
>			Howard Trickey
>			...decwrl!Glacier!Shasta!trickey

That's both good and bad:  bad because pc is non-standard, but good because
Berkeley refused to make it even more so.  In this respect, the standard
completer clause for the case statement is 
	"otherwise" statement-sequence
rather than "others" as a case-constant-list.
-- 
--Bill Price  uucp:  {Most Anybody}!sdcsvax!bmcg!bprice
              arpa:? sdcsvax!bmcg!bprice@nosc