Re: debugging and lambda variables

[Jim Meehan <Meehan@YALE.ARPA>]

The current  set  of  debugging  tools  is  weak, and sometimes the best
thing to do  IS  to  insert  print-statements.   While  the  "inspector"
(crawl) is  fairly  powerful,  the  user  interface  to it is also weak.
But designing and implementing a good debugging system  is  a  difficult
task, and  in  the  large  scheme  of things, has been assigned a fairly
low priority, and justifiably so.  Would you really ask the implementors
to postpone  work  on,  say,  garbage  collection to launch into a large
programming environments project?  It's simply too soon.

On the other hand, there are people working on T tools,  at  least  here
at CSI.   Just  slightly  more  helpful  than TRACE are BREAK and WATCH,
which were announced in T-USERS or some comparable bboard quite a  while
ago.  We're  also  working  on  inspector-like  programs,  and somewhere
on our wish-list is  the  use  of  graphics  to  aid  in  this  process.
(Example:  the  stack is all written out vertically.  You put the cursor
next to one frame, hit some command key, and  a  "subwindow"  opens  up,
showing you  the  details  of  that  frame.  Etc., etc.)  Many debugging
systems, not just  T's,  are  suited  to  a  hardcopy  technology,  with
"command lines"  and  printed  displays  of  information.  Bringing them
into the bitmapped age is difficult.  Consider the  complexity  of  some
of the  fancy  tools  such as the Programmer's Assistant from Xerox, and
you'll know why this isn't an easy task.
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