Re: [Emacs-diffs] master 176a617: Add filter macro, which does what you expect.

[Stefan Monnier]

> +     * subr.el (filter): New macro. Because it's just silly for a Lisp
> +     not to have this in 2014.  And VC needs it.

Elisp does have it.  It's called cl-remove-if-not.

> +(defmacro filter (condp lst)
> +  "Return the list consisting of elements in LST for which CONDP is not nil."
> +  `(delq nil
> +      (mapcar (lambda (x) (and (funcall ,condp x) x)) ,lst)))

Why define this as a macro, when it's obviously intended to behave as
a function?  And of course, this will misbehave if one of the elements
that should be kept is nil.

Also, we have a seq-filter in the new seq.el library that's pending
inclusion, so this poorly cobbled-up `filter' in subr.el is definitely
not welcome.


        Stefan