Software Visualization....

Matthew McDonald mafm at
Thu Oct 22 01:46:05 UTC 1998

Mark Wai writes:
 > I took a quick peek at ZStep.  To be honest, I don't see anything that is
 > different or new (in terms of ideas, concepts and implementation) from
 > standard ST debugger.  

I'm new to smalltalk and therefore don't know much about standard
smalltalk debuggers, but doesn't ZStep have reversible execution (or
some sort of simulation of it)?

Can standard smalltalk debuggers (or the squeak debugger) do this?

[I found reversible execution to be a surprisingly useful feature in
practice. Most bugs seem to be either (a) errors that are immediately
apparent, and easy to spot from a static view of the activation stack
when they occur, or (b) the result of some earlier computation doing
something that caused a problem that only becomes apparent later -
these can be much harder to locate. ("Where did variable X get set to
that stupid value? -- I know, I'll run the program backwards to the
point where it was last set.)]

Matthew McDonald <mafm at>

More information about the Squeak-dev mailing list