Re: master e910ef3: Improve bound-and-true-p doc string

Re: master e910ef3: Improve bound-and-true-p doc string

[Stefan Monnier]

>  (defmacro bound-and-true-p (var)
> -  "Return the value of symbol VAR if it is bound, else nil."
> +  "Return the value of symbol VAR if it is bound, else nil.
> +Note that if `lexical-binding' is in effect, this refers to the
> +global value outside of any lexical scope."
>    `(and (boundp (quote ,var)) ,var))

Hmm... the `boundp` indeed checks the binding of the dynvar of that
name, but the subsequent var reference will actually return the lexical
binding if there's one:

    (eval '(let ((sm-foo 4)) (set 'sm-foo 0) (bound-and-true-p sm-foo)) t)
=>
    4

I suspect that `boundp` should signal a warning when compiling such code
because using `boundp` or `bound-and-true-p` within the lexical scope of
a var with the same name seems like a good hint that the coder is
quite confused.


        Stefan

Re: master e910ef3: Improve bound-and-true-p doc string

[Lars Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Hmm... the `boundp` indeed checks the binding of the dynvar of that
> name, but the subsequent var reference will actually return the lexical
> binding if there's one:
>
>     (eval '(let ((sm-foo 4)) (set 'sm-foo 0) (bound-and-true-p sm-foo)) t)
> =>
>     4

Oh yeah -- it's not really a meaningful function at all when referring
to a lexically bound variable.  I've now updated the doc string further.

> I suspect that `boundp` should signal a warning when compiling such code
> because using `boundp` or `bound-and-true-p` within the lexical scope of
> a var with the same name seems like a good hint that the coder is
> quite confused.

Yes, sounds like a good idea.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no