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From: dwp@willett.pgh.pa.us (Doug Philips)
Newsgroups: comp.lang.forth
Subject: Re: DOER..MAKE
Message-ID: <1497.UUL1.3#5129@willett.pgh.pa.us>
Date: 10 Aug 90 03:33:06 GMT
References: <9008081745.AA29723@ucbvax.Berkeley.EDU>
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 82


MB>Another common technique is the DOER ... MAKE construct described in
MB>_Thinking Forth_ .  Personally, I do not like DOER ... MAKE because it
MB>adds yet another non-postfix syntactic construct to Forth.

CE> I'm surprised you feel this way. The DOER...MAKE construct strikes me
CE> as being no more non-postfix than the _double_ non-postfixedness (??) of
CE> both ' and IS with DEFER.

Just checked my copy of _Thinking Forth_.  Most of the book is sprinkled
with quotes from various people, CM included, that support the authors
position.  The section on DOER ...  MAKE is prefaced with:

	The traditional techniques for implementing vectored execution
    are described in _Starting Forth_, Chapter Nine.  In this section we'll
    discuss a new syntax which I invented and which I think can be used
    in many circumstances more elegantly than the traditional methods.

There are no quotes in the 6 pages he takes to describe and give examples
of his two new words.  I think that that lack of quotes is significant.
In the end, I agree with Mitch on this point.

MB> Every non-postfix contruct detracts from the regularity and
MB> understandability of the language, because non-postfix constructs
MB> behave differently in different states.  They are also difficult to
MB> decompile and difficult to metacompile.

This argues strongly against adding non-post-fix constructs.  I don't think
it is powerful enough an argument to rule out any non-post-fix constructs.

MB> MAKE is particulary troublesome because it introduces yet another way
MB> to start a colon definition.  There ought to be just one way to start
MB> a colon definition, but there are currently 2 ( : and DOES> ), and
MB> MAKE is a third.
    [ . . . -dwp]
MB> Similar comments apply to DOES> ; the problems with DOES> were recognized
MB> many years ago ("A New Syntax for Defining Words" Bill Ragsdale, Forth
MB> Dimensions, Vol.2 No.5, Jan. 1981).

Ok, so I'll ask the obvious question, though it isn't really a technical
question:  _Why_ hasn't Ragsdale's idea caught on?  I just skimmed the
article and it made a lot of sense to me.  On the other hand, I'm a novice
to Forth, so "made a lot of sense to me" could be a bad sign.

MB> lies in the fact that it is sort of like English.  Unfortunately,
MB> Forth syntax isn't very much like English in any other way, so
MB> trying to use English as a guide is not likely to be productive.

Chuck Moore (as quoted by Brodie in _Thinking Forth_, page 262)

	I would distinguish between reading nicely in English and
	reading nicely.  In other languages such as Spanish, adjectives
	follow nouns.  We should be independant of details like which
	language we're thinking in.

	It depends on your intention: simplicity, or emulation of
	English.  English is not such a superb language that we should
	follow it slavishly.

MB> In my oponion, most of the technical problems with Forth arise from
MB> places where Forth departs from its postfix heritage and attempts to
MB> be "like English".  CREATE is the prime example.

I think there is a distinction to be made here.  As I understand the
simplifying power of Forth, and with simplicity in general, one *can*
take it too far.  I'm inclined to agree with you here.  I would like
to see a standardize kernel that is much more postfix.  From that
you can build the "friendly" user stuff without making it hard to write
programs that write programs.

MB> An important test of power: The Forth Way can be defined in terms
MB> of the Right Way, but not vice versa, e.g.

I don't know that I'd want to buy into the morality of "the Right Way",
but I think the point about expressiveness and power is true.


-Doug

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