The "seq" in "seq-contains?" says "I want a sequential search."
Protocols *could* make this do something different, but that would
violate the contract of this function.
Another way to put it: If you wrote a protocol to pick a fast
implementation based on type, then seq-contains? would be the fn that
the protocol would call if it couldn't find anything faster.
There have to be primitive things somewhere...
Stu
On 2010 Apr 28, at 5:32 PM, Meikel Brandmeyer wrote:
On Wed, Apr 28, 2010 at 05:26:46PM -0400, Douglas Philips wrote:
How is having an optimized version of seq-contains? for sets/maps
any different from what Stuart showed in his video, where reduce can
have a specialization that is faster on some types?
A faster reduce is still O(N). If you need fast lookup use the
correct
data structure. If you do linear search it's gonna be slow, so make
it
clear in the code! This makes the developer aware of the
implications.
Stuart's comment was to not use seq-contains? on maps or sets.
There is no reason that it cannot be the same speed as contains? if
a set or map is passed in.
Wasn't the whole point of having sequences as an abstraction to get
away from all the cruft that traditional lisp had built up around
concrete types? Why go back to that here? Can't protocols handle
optimizing this case?
If some function I call uses seq-contains? (so that it can get all
the wonderful seq-ness abstractness clojure offers) I should have to
know that internal detail and not pass in a map or set? or worse,
fail to get an optimization in that case? C'mon, this should be an
easy protocol win (or maybe I don't really understand the limits on
what protocols can do.)
-Doug
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