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From: mj@myrias.UUCP (Michal Jaegermann)
Newsgroups: comp.lang.forth
Subject: Re: Debugging Aids for Forth
Message-ID: <523@myrias.UUCP>
Date: Fri, 21-Aug-87 16:01:23 EDT
Article-I.D.: myrias.523
Posted: Fri Aug 21 16:01:23 1987
Date-Received: Sun, 23-Aug-87 06:17:12 EDT
References: <3623@ihlpg.ATT.COM> <1516@crash.CTS.COM>
Reply-To: mj@myriasa.UUCP (Michal Jaegermann)
Organization: Myrias Research Corporation
Lines: 28
Keywords: debug, trace


     I agree with all comments made here about Forth being its own 
symbolic debugger, writing small words with meanigful names and so on.
Still one problem remains, exemplified by a novice tendency to use
to many variables in a code.  One - good - reason for that is that
one cna be easily lost in a "stack jungle" created quite easily,
even if your words are small and simply.  And you need some experience
and practice to discard all this "stack noise" (ROT, DUP, OVER,
SWAP.....) when reading a code.  One proposition was to execute
"problem" words by typing components one by one.  I am just too lazy for
that, so in one of my Forth systems I included a tracing facility into
a screen editor which I wrote (I was unhappy with the original editor).
A certain key combinations caused an an execution of word (or two words -
if needed) and display a stack contents at the bottom of a scree.
A great debugging, teaching, learning ans demonstration tool.  And very
easy to implement in Forth, since all needed componenets are already 
in place - by the language design.  Details may vary a little bit, due
to implementations peculiarities, but basically you have to grab
a string of characters from screen and move cursor past it
(ENCLOSE willdo the job and provide information needed) change it to
an address (this is a job of FIND) and pass it to inner interpreter
to execute it (it was designed to do exactly that).  That's all and
some extra bells and whistles can be easily added.

     Michal Jaegermann
     Myrias Research Corporation
     Edmonton, Alberta, CANADA
     ....ihnp4!alberta!myrias!mj