Re: Lexical binding

[Christian Ohler <ohler@gnu.org>]

On 3/04/11 4:57, Juanma Barranquero wrote:
> The original trouble with `loop' is that, in a loop like this one,
> with destructuring
>
>   (defsubst my--bs-file-width ()
>     (- (window-width)
>       (loop for (name width . rest) in bs-attributes-list
>           if (numberp width) sum width)
>        (bs--get-name-length)
>        1))
>
> `name' is just a placeholder (as it is rest). I'm interested just in
> `width'. And there's no way to write that loop as is without warnings.

In loop destructuring, you can use nil for fields that you want to ignore:

      (loop for (nil width . nil) in bs-attributes-list
	   if (numberp width) sum width)

If you want to keep the ignored fields named, you could do something like

      (loop for (name width . rest) in bs-attributes-list
	   do (progn name rest) ; ignore
	   if (numberp width) sum width)

Christian.