RE: Wrong type argument: arrayp, nil

[Drew Adams]

> Is there a debug tutorial somewhere or d and c and q is all that is needed
> in real life?

See the Elisp manual, node `Using Debugger'.  See in fact all of the nodes
under node `Debugger'.

> How does you debug-edit-debug cycle look like? Is C-x C-e all I should be
> using or is there something that has a concept of 'a breakpoint'?

You can place an explicit call to `debug' in the source code (or a copy
of the source code, anywhere you like.  That makes the debugger enter at
that point.