1.7 KiB
Common Lisp
Blogs
Debugging
Add this to set SBCL to have debug mode enabled.
CL-USER> (declaim (optimize (debug 3)))
NILThis is broken because of the divide by zero:
(defun fib (n)
(if (<= 0 n 1)
(/ 1 0)
(+ (fib (- n 1))
(fib (- n 2)))))
Running the above puts us in the debugger once we hit the base case, but we can edit the
function definition by adding (break) and then press r on the frame we wish to restart.
Once we fix the code we can restart stepping and the issue can be fixed live!
(defun fib (n)
(break)
(if (<= 0 n 1)
(/ 1 0)
(+ (fib (- n 1))
(fib (- n 2)))))
You can toggle C-c M-t (slime trace dialog) on a funcion and then invoke it and then view the results with C-c T.
update-instance-for-redefined-class is handy for defining migration behavior when you need to redefine a class.
Restarts can be a handy tool where throw/catch would normally be used. Restarts allow for a user-defined failure functionality to be selected while still maintaining control in the function which caused the error.
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