I make much use of `aput' from assoc.el in my .emacs. It lets me modify
the value associated with a certain key in an alist, where keys are
compared with `equal'.
I often saw people reinventing this function who didn't yet know
assoc.el. Now, assoc.el is obsolete. I'm not against that, since there
were not many useful things in assoc.el besides `aput'.
But I wonder if there is a simple replacement for `aput' in vanilla
Emacs? I don't think so, but maybe I have overseen something.
If not, can we add a new function `assoc-delete-all' to subr.el (which
would be like `assq-delete-all', but would compare keys with `equal'
instead of `eq')? Dunno why this function does not exist yet, but it
would ease handling alists e.g. if its keys are strings.