Notes 6/7/23

common-lisp.org

@@ -0,0 +1,49 @@
+#+TITLE: Common Lisp
+#+AUTHOR: Adam Mohammed
+
+* Blogs
+-  [[https://malisper.me][malisper.me]]
+
+* Debugging
+Add this to set SBCL to have debug mode enabled.
+#+begin_src lisp
+CL-USER> (declaim (optimize (debug 3)))
+NIL
+#+end_src
+
+This is broken because of the divide by zero:
+#+begin_src lisp
+  (defun fib (n)
+    (if (<= 0 n 1)
+	(/ 1 0)
+	(+ (fib (- n 1))
+	   (fib (- n 2)))))
+#+end_src
+
+
+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!
+#+begin_src lisp
+  (defun fib (n)
+    (break)
+    (if (<= 0 n 1)
+	(/ 1 0)
+	(+ (fib (- n 1))
+	   (fib (- n 2)))))
+#+end_src
+
+
+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.
+
++ References:
+  - [[https://malisper.me/debugging-lisp-part-1-recompilation/][Recompilation]]
+  - [[https://malisper.me/debugging-lisp-part-2-inspecting/][Inspecting]]
+  - [[https://malisper.me/debugging-lisp-part-3-redefining-classes/][Redefining Classes]]
+  - [[https://malisper.me/debugging-lisp-part-4-restarts/][Restarts]]
+  - [[https://malisper.me/debugging-lisp-part-5-miscellaneous/][tricks]]