Re: more on compiler warnings about unused vars

[<pj...@in...>]

don...@is... (Don Cohen) writes:

>  > You realize that the reference to b in the progn is dead code.  So it's
>  > eliminated, So b is not referenced anymore.
> Yes, but it used to at least be a useful way to avoid the warnings.
>
>  > Unfortunately, in loop, there's no place for declarations about loop's
>  > variables.  The loop macro itself could have an ignorable declaration
>  > for them but I don't remember if that would be conformant, and it would
>  > be questionnable anyways: the warning is good: did you really not make a
>  > typo?
> In all of the cases involved there was no typo.
> I ended up rewriting things like
>  (loop for x in a collect 'input) 
> to
>  (loop for x below (length a) collect 'input)
> I still have code like
>  (loop for (x y z) in a collect y)
> I really don't like to use nil there but I could.
>
>  > > I was even getting "not read" warnings from my loop extension in
>  > > cases like this
>  > >  (loop for (a b) s.t. (r a b) collect a)
>  > Too bad you don't say what s.t. is...
> such that
> in general
>  (loop for [variable list] s.t. [well formed formula] ...)
> see ap5.com for more detail

Ok.  Well, without looking at the source of the implementation of
s.t. it should be noted that in general loops may provide the variables
as a new binding in each loop iteration, in which case even if you use
it in the wff, the one you get in the body will be a new binding, and
this is probably that one that is not used.  In this case indeed, you
cannot use nil, so you must use the variable.  Perhaps like this:

(loop for (a b) s.t. (r a b)
      collect (let ((b b))
                 (declare (ignore b))  
                 a))


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/