Debugger Commands

The user interface is not very sophisticated, but undoubtedly it will have more commands in the future. If you have suggestions of what would be useful, feel free to contact me. The commands are:

val sym

gives the value of sym in the current scope.

set! sym val

sets the value of sym to val in the current scope.

g

continues evaluation until the next breakpoint

c

clear any breakpoints on the current line. Also clears break on entry specified with psd-break.

w

shows the current context as file name and a list of procedure names. For example, "/tmp/killme.scm:(encode encode-symbol)" means, that the you are in file /tmp/killme.scm, inside a procedure called encode-symbol, which is inside the procedure encode. I am considering removing this feature, because I don't remember using it at all myself.

s

steps one step in the evaluation process. Each time an expression is about to be evaluated, psd displays it and waits for a command. When an expression has been evaluated, psd displays the result and waits for a command.

n

continues evaluation until evaluation reaches a different line

r expr

evaluates expr and returns its value as the return value of the current expression

A list is taken to be a procedure call that is to be evaluated. All the essential procedures in R4RS are visible to the evaluator. Any other command displays a list of available commands.

If the debugger does not seem to be doing the right things, try the Emacs command M-x psd-reset, which will clear all the breakpoints and reset the runtime system.