Re: trace

[cld@xxxxxxxx (Carl Distefano)]

Reply to note from "morris krok"  Sun, 27 Feb
2005 13:04:50 +0200

> I tried the Trace program, but it does strange things in both
> windows by adding other code to the original program. An
> explanation of code does appear on the prompt line if I keep
> on pressing F9 or the enter key whenever it stops for it to
> move to the next command. This does not seem right to me.

TRACE works that way by design -- as you'll see if you read the Help
screen (command HELP TRACE). It emulates for XPL the
visual tracing/debugging capabilities of other programming
environments (e.g., Visual Basic).

As you may know, XPL has a built-in tracing facility, default DB
(for DeBug). Even at its maximum setting, however (Default DB=7),
the PRompts are less informative than in TRACE; crucially, DB lacks
lacks TRACE's ability to display Save/Get contents during program
execution. That's why TRACE has to modify the subject code -- to
extract additional information that the native facility doesn't
provide. (And fiendishly clever those mods are, too.)

If you want to play with default DB, you can get help on the various
settings (1-7) with HELP VA $DB. (See also Signature:
Making the Transition, p. 5-10.) Be sure to clear DB when you're
done (command Default DB=0). An active DeBug setting will wreak
havoc with U2 or any XPL-dependent XyWrite setup.

--
Carl Distefano
cld@xxxxxxxx