Path: utzoo!utgpu!attcan!uunet!nuchat!sugar!ssd
From: ssd@sugar.uu.net (Scott Denham)
Newsgroups: comp.lang.fortran
Subject: Re: Is DO WHILE difficult?
Summary: OK, maybe not DO WHILE!
Message-ID: <2963@sugar.uu.net>
Date: 7 Nov 88 05:56:06 GMT
References: <75326@sun.uucp> <75328@sun.uucp> <604@quintus.UUCP> <11222@cgl.ucsf.EDU>
Organization: Sugar Land Unix - Houston, TX
Lines: 30

In article <11222@cgl.ucsf.EDU>, seibel@cgl.ucsf.edu (George Seibel) writes:
> 
> And in another article, ssd@sugar.uu.net (Scott Denham) writes:
> 
> >just wake up one morning and decide it would be nice to add say, a new 
> >loop construct (DO WHILE ?) to their compiler.  These extensions cost the
> >developers a signifigant amount of money.  [...]
> 
>  ... I'm not a
> compiler writer, but for the life of me I can't see how some features
> like blank line == comment, or  "!" == inline comment, or the
> implementation of a DO WHILE are all that tough!   Wouldn't these
> George Seibel, UCSF

I for one, George, have no idea how difficult these things are. I chose
DO WHILE only as an example, and only because it happened to be floating
by on some neuron at the exact moment my fingers reached that point in
the sentence.  A better feature to use would be one that doesn't exist
but everyone would understand.  
One thing I have heard argued (and I've seen some pretty good examples)
is that it's not the individual features that cause the compiler writers
all the headaches, but the sheer number of possibilities. A couple of 
years ago somebody at IBM "cleaned up" the logic for handling implied
DO loops in WRITE statements.  I was astonished at how long it took to
get the "cleaned up" code cleaned up, and at the obscure and strange 
things that popped out of the old "dusty decks" when this happened.
 
   Scott Denham 
    Western Atlas International