Re: if-let and when-let: parallel or sequential

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Why do you think so?  If they only work for a single binding, the
> benefit is really minor.  It's only when you use several bindings that
> the benefit becomes more significant (the alternative being either
> a very deeply nested code, or separating the var's declarations from
> their initialization).

I use lw:when-let all the time in Common Lisp.  It only takes a single
binding.  I find it very clear and nice -- mostly used as a kinda "early
return" thing, but without the return.

(defun foo (zot)
  (when-let (bar (compute-something zot))
    ...))

I grepped through a random directory in our code base, and out of 146
uses of when-let, 6 had nested when-lets.

There's lw:when-let*, though, which is like Emacs' when-let (i.e.,
several bindings), which is used two times.

Anyway, I think Emacs' when-let is a good addition as it is now.  Even
if the multiple-let-binding version doesn't get used much, it's nice
when you need it.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no