RE: Predicate for true lists

[Drew Adams]

> > Anything that mentions state (which could be _any_ state
> > available to Emacs - not just system state
    ^^^^^^^^^^^^^^^^^^

> I think the most important thing is the state of Emacs: variable
> bindings (free variables in the function body!), current buffer, value
> of point, etc.  Since only stuff matters that Emacs has access to (and
> this access is always via functions and variables), one could even count
> everything that matters as part of Emacs' state.
> 
> What I want to say that mentioning too much external stuff as examples
> is more confusing than helpful.

I agree.  That's most important, by far.

(OTOH, if we're trying to give a general definition
of pure then any state at all counts.  Still, it's
only possible for a computable function to take
into account state that is available to it...)