LISP DEBUGGING OVERVIEW
CMSC 471 -- FALL 2010
Thanks to Marie desJardins


DEBUGGING COMMANDS:

:h	  Print a list of available commands
:a	  Abort to the next debug level
:q	  Abort to the top level interpreter
:e	  Print the last error message
:i	  Inspect the last error message (can get to local variables etc.)
:w	  Print the current stack frame
:u	  Go up one stack frame (i.e., to the caller)
:d	  Go down one stack frame (i.e., to the callee)
:t	  Go to the top frame (top-level expression being evaluated)
:b	  Go to the bottom (most recent) frame
:bt	  List the stack from bottom to top
  :bt1 - :bt5    List the stack with varying levels of detail
:fl	  Set the frame limit (how many frames to print in backtrace)
:rt	  Return from the current frame (prompts for return values)
:c	  Continue evaluation (if at a continuable error)
:rd	  Re-evaluate the current stack frame


STEPPING COMMANDS:
(step EXPR)	Single-step evaluation of EXPR
:s		Evaluate the current form in single step mode
:n		Step over a form (evaluate one form in batch mode)
:o		Step over a level (evaluate the rest of the current
		form up to the next return)
:c		Turn off single step mode and continue evaluation


OTHER DEBUGGING FACILITIES:
(inspect EXPR)	Inspect an arbitrary list object (can "dive in" to examine
		components of a structured object)
(trace FN-NAME)	Trace a function (print information every time the function 
		is invoked or returns)
(untrace FN-NAME)   Untrace a function
(untrace)	Untrace all functions
(break)		Go to a break level (continue by typing :c)
(break FORMAT-STRING ARGS)    Go to a break level and print a formatted
			      message