bug#25581: 25.1; Incorrect statement in (elisp) `Hooks'

[Drew Adams <drew.adams@oracle.com>]

> I think the confusing thing here is that there are two ways to modify
> these single function hooks: setq and add-function.

`setq' can always be used to change a variable's value.
But that doesn't mean it's always the best thing to use.

See earlier posts in this thread, about variables whose
value is a "single function".  They can be hooks, but
need not be hooks (and this, regardless of their names).

Some vars are _intended_ to only ever have a single
function as their value.  Some vars are _intended_ to
have a value that can be a single function or a list of
functions.  Some of the latter kind of variables are
hooks.  (Maybe _all_ of the latter can be treated as
hooks; maybe not.)

`add-hook' is the best way to add a function to a hook.
This is so, regardless of its name.  That you can use
`setq' or something else instead doesn't make that TRT.