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From: dgary@ecsvax.UUCP
Newsgroups: net.lang,net.lang.forth
Subject: Re: FORTH efficiency
Message-ID: <2867@ecsvax.UUCP>
Date: Mon, 9-Jul-84 14:45:45 EDT
Article-I.D.: ecsvax.2867
Posted: Mon Jul  9 14:45:45 1984
Date-Received: Wed, 11-Jul-84 03:37:59 EDT
References: lanl-a.9623
Lines: 38

<>
The referenced article notes that FORTH is often not efficient when
compared to compiled languages, giving as an example the phrase

A @ B @ + C !

and its FORTRAN equivalent C=A+B.  Two comments:

First, FORTH is properly advertised as a fast, space-efficient interactive
development language.  The operative word is 'interactive' which almost
(obviously, not quite) implies 'interpretive'.  FORTH is rather speedy as
interpretive languages go.  Furthermore, all 'real' FORTHs include an
assembler so that time-critical routines (typically a small part of
most applications) can be coded in assembler and then tested interactively.
FORTH is often best used as an interactive assembler.

A few ridiculous claims have been made for FORTH speed.  The most ludicrous
is the assertion that FORTH code often executes faster than the equivalent
assembler program (!!!) an outrageous claim from no less than a FORTH
Interest Group (fig) brochure.

As for the example given, it is possible to speed it up by using constants
instead of variables, and writing a FORTH word that stores a new value in
a constant.  That would make the phrase something like:

A B + := C

(The := word has to be IMMEDIATE and is best done in assembler, but

: := ['] ! ; IMMEDIATE

would probably work (haven't tried it), although you may need to
get rid of the brackets.)

D Gary Grady
Duke University Computation Center, Durham, NC  27706
(919) 684-4146
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