thomas.mertes@[EMAIL PROTECTED]
wrote:
>
> Pascal 6000 which predates P4 already had an 'otherwise'
> clause. IMHO it was a big mistake to omit it in the P4
> compiler and in the ISO 7185 standard. Do you plan to
> add 'otherwise'/'else' to the P5? Since I switched
> from Pascal to C in the early 90s, I am not sure if
> modern Pascals prefer 'otherwise' or 'else' for 'case'
> statements.
Yes, it was (the otherwise) an extension that was local
to the University of Minnesota version.
Remember that the P4 compiler was designed in the 1970's
by Wirth's students in Zurich, and was not designed to implement
the entire Pascal language as it existed at that time, it was
deliberately subsetted.
I have considered P4 to be a historical item. There are actually
a lot of copies running around the net, as you have seen in
this thread (Steve pemberton has a copy, so does the CDC 6000
history group). I updated it to be ->source<- compliant with
ISO 7185 because otherwise, I wouldn't be able to compile it,
since I don't use a CDC compiler from the 1970s (even the 1984
CDC 6000 compiler would have refused to compile it in the
original form). Of course it would be useful to also have
a more modern, updated P4, which I did, and called it P5.
Now, lets go over my plans for P5 (and beyond), then lets
go over yours :-)
1. P5 was P4 brought up to accept ISO 7185 as well as to be
written in ISO 7185. Basically ISO 7185 is the 1970's Pascal,
with clarifications made by the Pascal standards committees.
It is P4 with the "subsetting" removed.
2. I agree that P5 should go further, such as extended
constructs. I would tend to call that P6 or more (p7, p8, etc).
Of course, its according to time permitting.
How about your plans? Its really up to you if you want to go
to town adding new constructs. That's what Wirth wanted when
he (they) issued the P4 kit.
So I would say, if you want an otherwise clause, that would
be a good starting place for you to get used to
changing/extending the compiler!
Remember that Steve Pembertons description of the P4 compiler
is online, and so are other original do***ents on it written
back in the 1970s (see the
http://www.standardpascal.org/do***ents.html
section on the
website).
P5 adds new SC (Stack Computer) operation codes, but the changes
are well do***ented in the source, so the P4 do***entation plus
the source will be adequate. I also hope to produce more
sup****ting do***ents for the P5 compiler in the near future.
>
> BTW.: Under which license is the P5 released?
> GPL would be great.
> Would there be a conflict the public domain P4 and the GPL?
>
> Greetings Thomas Mertes
I don't see any. Public domain is a centuries old concept, and
the P4 compiler has been public domain since the 1970s (since
it was created).
Of course, it is debatable what GPLing a public domain software
means, since anyone can take the old, public domain version of
the P4 compiler and do whatever they want with it, without
regard to the GPL.
It seems to me that what you would be effectively doing by
taking a P4 or P5 compiler, changing it and GPLing that, would
be that nobody could use your version of the compiler without
obeying the GPL.
In the immortal words of Billy Crystal, "yee hah", have fun with
the code.
Scott Moore
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