Re: lexical-binding question

[Michael Heerdegen <michael_heerdegen@xxxxxx>]

Katsumi Yamaoka <yamaoka@xxxxxxx> writes:

> The following forms are utmost simplified model of the functions
> that the above form uses:
>
> ;; -*- lexical-binding: t -*-
> (defun fn1 () ;; simplified `w3m-w3m-expand-arguments'
>   (eval '`,charset))
>
> (defun fn2 (charset) ;; simplified `w3m-rendering-half-dump'
>   (ignore charset) ;; Silence the byte compiler.
>   (fn1))
>
> (defun fn3 (&optional charset) ;; simplified `w3m-rendering-buffer'
>   (fn2 charset))

CHARSET is a lexical variable in fn2 and fn3.  Its scope is limited to
(textual) references in those functions.  The lexical binding is not
visible in fn1 no matter what eval '`, tricks you try, because it's out
of scope.  It would only work as you expect with a dynamically bound
variable.

You can either make `charset' special (that can even be done locally in
the function) to reuse the old code, or you rewrite that stuff so that
it's really lexical binding code.  Then w3m-halfdump-command-arguments
would probably become a function `w3m-halfdump-get-command-arguments'
that depends on an CHARSET argument, or something similar.

BTW, `eval' without second argument does evaluation with dynamical
scoping.  But it doesn't make a difference, because the call is outside
of scope anyway.

Michael.