On Thu, Mar 11, 2010 at 2:36 PM, Chouser <chou...@gmail.com> wrote: > On Thu, Mar 11, 2010 at 2:19 PM, Brian Hurt <bhur...@gmail.com> wrote: > > So the doc comment on empty? reads, in part: > > > >> Please use the idiom (seq x) rather than (not (empty? x)) > > > > A heads up to people: these two code sequences are *not* identical in > > behavior: > > > > user=> (seq? '()) > > true > > user=> (not (empty? '())) > > false > > What you demonstrated is that (seq x) is not the same as > (seq? x) -- useful to know, but not the point of the docstring. > > Also note that it's not necessary or idiomatic to quote the empty > list: > > user=> (seq ()) > nil > > Point.
I think I still disagree with this idiom, for two reasons. First, I have the hope that some day Clojure will be smart enough to realize that the boolean returned from empty? can be unboxed, and unbox it (with all the performance optimizations this allows). seq doesn't allow this optimization- in the non-empty case it returns a cons cell, which will (almost certainly) never be unboxable. My second objection is that it sets a bad precedent. The core library sets the tone for the language- it's the main example of how you write code in the language. Caesar's wife must be above reproach. And depending upon a specific, corner-case behavior of a function whose main purpose is do something else is a practise that will burn you badly. That being said, I'm just going to agree to disagree, and move on. Brian -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
