🚀 go-pugleaf

In article <5@f.gp.cs.cmu.edu> rpd@f.gp.cs.cmu.edu (Richard Draves) writes:
>I don't believe a true one-pass Modula-2 compiler is possible.
>I have some experience with the language, having implemented
>the front-end (first-pass) for a compiler.  I have also discussed
>this issue with Mike Powell, implementor of the famed Powell compiler,
>and he concurs.
>
Yes, the compiler is possible.  In fact, I have used it.  This is
sometimes called the Heitz compiler as Wener Heitz (sorry about name
spelling) as well as good ol' Nick W. worked on it.  I know many who
are using the Lillith version and love it.  I have used the Macintosh
version called "MacMETH" - beware as this version as SERIOUS BUGS.  I
have had Keith Poole from Modula Corp help me out and he agrees that
the Mac version has serious bugs.  Modula Corp does not get any
support from ETH on this product, so he can't help me out.  I have
also found serious bugs in MacModula-2 (all versions) dealing with
their handling of processes (coroutines).

You have to remember that the definition of the language has changed
(again, sigh!) for the one-pass compiler.  There are no export
statements as everything in the definition module is exported.
Coroutines are no longer part of the definition of the language - but
many implementation will still have them I hope.

One great thing about it - IT IS FAST.  MacMETH compiles about 40-100
times faster than MacModula-2.  I suppose similar speed-ups are
obtained elsewhere...

By the way, about the Powell compiler - I have also hit some serious
bugs there.  I have been able to call procedures with the wrong number
of arguments and it links!  How did this happend?  Well, I was
changing a module around and made the number of parameters in some
procedure calls different.  Some people came around to distract me and
we went out to lunch...  Later, I forgot to change the module that
holds the calls to these changed procedures and I ran my makefile.
Well, my makefile was not made properly, so all it did was recompile
the files that had been edited and linked them - successfully!!!  It
did not do any checking for me.  I realize that this goof was
initially my fault (almost all bugs are), but a strictly typed
language such as Modula-2 is suppose to check this...  Since
everything compiled and linked, it took me quite a long time to track
this down with the debugger.

>The problem is that identifiers may be used in statements before they
>are declared (although identifiers used in declarations must be declared
>before use).  Page 145 of the 3rd edition of Wirth's book is very clear.
>You may think a back-patching scheme can overcome this, but I have some
>sample programs that I think can convince anyone that the problems with
>such an approach are intractable.
>
>Does this purported one-pass compiler compile the whole language or a subset?
>If it does compile the whole language, does anyone know how it accomplishes
>this in a single pass?  Let me mention that reading a program into memory,
>perhaps in the form of a syntax tree, and then generating code is *not*
>one pass.
>
This I don't know about - I suppose you might contact the people at
ETH and/or Modula Corp for an answer.



-- 

Herb Barad	[USC - Signal and Image Processing Institute]

USENET:		...!sdcrdcf!usc-oberon!brand!barad			or
		...!mcvax!seismo!sdcsvax!sdcrdcf!usc-oberon!brand!barad

ARPANET:	barad@brand.usc.edu

USMail:		Univ. of Southern California
		Powell Hall 306, MC-0272
		Los Angeles, CA 90089-0272
		phone: (213) 743-0911