Debugger Commands

These are commands that you can give when the program has been stopped to a breakpoint, and the prompt says psd>.

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.

c

clears all breakpoints on current line

g

continues evaluation until the next breakpoint

w

shows the current context as file name and a list of procedure names. For example, if the context is "/tmp/killme.scm:(encode encode-symbol)", it means, that the you are in file /tmp/killme.scm, inside a procedure called encode-symbol, which is inside the procedure encode.

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.