Agreed: Rich's explanation is the more important bit.
My point is that we may be wasting time arguing about something that
nobody actually does. If idiomatic usage changes as the community
grows, we *could* add a collection-generic contains.
While I have no position on seq-contains?, I question this
methodology, which I've seen a few times now. It's early days for
Clojure, you're sampling a very small codebase, and there may be as
yet unforseen idiomatic uses (such as you point out for testing)
which invalidates this argument. In addition I think you may be
begging the question somewhat. Rich's explanation is more sound than
this argument.
On 29/04/2010, at 9:40 PM, Stuart Halloway wrote:
"In theory, there is no difference between theory and practice. In
practice, there is." -Yogi Berra (maybe).
The recent thread on the new seq functions spun off into a
theoretical discussion about whether about the merits of having
contains? and seq-contains? as separate functions. I would like to
ground that discussion with some observations from real-world use:
Doing an O(n) search of a seq (via includes? or, under its new
name, seq-contains?) occurs the following number of times in
various libraries:
Clojure: 0.
Contrib: 0.
Compojure: 1. (and it's wrong--should be a set test)
Incanter: 0.
(There are a few calls to seq-contains? in the test suite for
contrib, and I wrote all of them. If you write lots of unit tests
you already know why such calls make sense there.)
Also, AFAICT, there are *no* examples of using instance checks to
select the right containment function. So the theoretical concerns
about this issue have basically no exemplars in practice.
"In theory, you may be right about 'contains?.' In practice, Rich
Hickey is right." - Stu Halloway. :-)
Antony Blakey
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