Re: Can free variable refers to a lexical environment?

[Barry Margolin <barmar@alum.mit.edu>]

In article 
<180666d9-2ecb-4d99-a419-739650a8fb3d@c37g2000prb.googlegroups.com>,
 IWAKI Hidekazu <i.hidekazu@gmail.com> wrote:

> Hello,
> 
> I need to make a table factory function in emacs with cl extension.
> but I'm scheme user. I'm confusing emacs lisp behavior.
> will you please tell me the emacs lisp's free variable issue.
> 
> my table factory function is following code:
>  (defun mk-table-instance ()
>   (let ((table nil)) ;; create a lexical value `table`
>     (defun __temp__ (msg &rest value)
>       ;; some operation changes the lexical variable `table`
>       (case msg
> 	((push) (push (car value) table))
> 	(otherwise table)))
>     (function __temp__)))
> ;; return the `__temp__`  procedure with the lexical variable `table`
> ;; i.e. return a closure.
> 
> (fset 'table-object (mk-table-instance))
> ;; 'table-object is an unique procedure object.
> (table-object 'push 13)
> ;; my plan => operate an unique `table` variable which was created by
> involving `mk-table-instance`
> ;; real        => "Debugger entered--Lisp error: (void-variable
> table)"!!!!!!!
> 
> I researched this code. I guess the lexical binded variable `table` in
> `mk-table-instance` procedure refer to the global environment.
> In scheme, the variable refer to the lexical environment.
> 
> How to refer to a lexical environment?

Emacs Lisp implements dynamic scoping, not lexical scoping.

You can use lexical-let to emulate lexical binding.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
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