Variable predicate

Variable predicate

[Garklein]

In help-fns.el, two different ways are used to check if a symbol is a variable.

`describe-function' uses

(lambda (vv)
                  (or (get vv 'variable-documentation)
                      (and (not (keywordp vv))
                           ;; Since the variable may only exist in the
                           ;; original buffer, we have to look for it
                           ;; there.
                           (buffer-local-boundp vv orig-buffer))))

and `variable-at-point' just uses `boundp'.

Is there any difference between these two methods? Which should I use?

Thank you,
Garklein

Re: Variable predicate

[Sebastián Monía]

Hi Garklein,

I am not sure I am the most qualified person to reply, but if I am
wrong, we'll get corrections soon enough ;)

Garklein <garklein97@gmail.com> writes:
> In help-fns.el, two different ways are used to check if a symbol is a
> variable.
>
> `describe-function' uses
>
> (lambda (vv)
>  (or (get vv 'variable-documentation)
>      (and (not (keywordp vv))
>           ;; Since the variable may only exist in the
>           ;; original buffer, we have to look for it
>           ;; there.
>           (buffer-local-boundp vv orig-buffer))))

After checking the code, I think you meant this is how
'describe-variable' works.

The predicate is not checking "is the symbol a variable", but if it has
a documentation slot in its property list, -or- if it is bound
buffer-local.
The selection of symbols to run by the predicate comes from
help--symbol-completion-table which does....a lot more.

> and `variable-at-point' just uses `boundp'.

You can check this one using `describe-function' on `boundp' :)

> Is there any difference between these two methods? Which should I use?

They do very different things, if you _only_ want to know if a symbol
has been bound as a variable, boundp should be enough.

Hope that helps!

-- 
Sebastián Monía
https://site.sebasmonia.com/