protocol extensions are applied on a per-namespace basis. What you
describe shouldn't happen...it sounds to me that your tests for
heap1.clj somehow knows about the heap2.clj, otherwise
it wouldn't be possible to return an object from that namespace. In
fact, if you do a
lein test someNS.heap1
the protocol extensions for heap2.lj shouldn't run, unless there is a
dependency somewhere.
HTH,
Jim
On 26/09/13 13:10, Dustin Conrad wrote:
I am pretty new to Clojure, so what I am trying to do may make no
sense. I am completely open to alternative ways to get similar
functionality
I have a Heap protocol and two records that implement that protocol:
(defprotocol Heap
(min [this]
(insert [this x]))
In heap1.clj
(defrecord Heap1 [n]
(min [this] (comment do stuff))
(insert [this x] (comment insert stuff)))
In heap2.clj
(defrecord Heap2 [n]
(min [this] (comment do some different stuff))
(insert [this x] (comment insert stuff in a different way))
I found it useful to use extend-type to define this protocol on nil as
well.
In heap1.clj
(extend-type nil
Heap
(min [this] (throw (Exception.))
(insert [this x] (->Heap1 x)
This is all still working. In heap2.clj I would like to define
another implementation of heap on nil, for when I require/use heap2.clj .
In heap2.clj
(extend-type nil
Heap
(min [this] (throw (Exception.))
(insert [this x] (->Heap2 x)
Now, in the tests for heap1.clj where I am not requiring the heap2
namespace (or even know about it), my tests are failing because
(insert nil 1) now returns a heap2 record. At this point I decided I
obviously did not understand what extend-type actually does, and tried
to do a bit of research, but I couldn't really find anything that went
very in-depth.
If someone could provide an alternative to what I am trying to do,
that would be great. Alternatively, it would be useful for someone to
explain what extend-type does under the covers a bit.
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