Hmm, the different return types seem tied to the 2 different functions
being called, but both functions have the same return type, which is a
lazyseq. I am using Monger to get data from MongoDb. These functions are
private:
(defn- get-distinct [request]
{:pre [(= (type request) clojure.lang.PersistentHashMap)]
:post [(= (type %) clojure.lang.LazySeq)]}
(monger/get-distinct (:item-type request)))
(defn- paginate-results [request]
{:pre [ (= (type request) clojure.lang.PersistentHashMap)]
:post [(= (type %) clojure.lang.LazySeq)]}
(monger/paginate-results (:item-type request) (if (:which-page request)
(:which-page request)
0)))
Both of these functions return lazyseqs, as expected. The results from both
get run through a (reduce) function that does some minor filtering. Yet in
one case the return type (from the reduce function)
is clojure.lang.PersistentArrayMap and in the other it
is clojure.lang.PersistentHashMap. I'd like to be able to write a :post
condition that enforces strictness, but that seems impossible because I can
not figure out what the rule is that handles the conversion. I don't care
if the return type is clojure.lang.PersistentArrayMap
or clojure.lang.PersistentHashMap, all I want is it for it be consistently
one or the other.
On Sunday, December 22, 2013 2:31:45 PM UTC-5, larry google groups wrote:
>
>
> I am surprised that a map literal is clojure.lang.PersistentArrayMap but
> as soon as I assign it to a var, it becomes clojure.lang.PersistentHashMap.
> Are there any rules for being able to predict when these conversions occur?
>
> user> (type {})
> clojure.lang.PersistentArrayMap
>
> user> (type {:what "why?"})
> clojure.lang.PersistentArrayMap
>
> user> (def curious {:what "why?"})
> #'user/curious
>
> user> (type curious)
> clojure.lang.PersistentHashMap
>
> user> (def sug (assoc curious :whodoneit "mikey"))
> #'user/sug
>
> user> (type sug)
> clojure.lang.PersistentHashMap
>
> I am curious because I wrote a (reduce) function which mostly just builds
> a map:
>
> (assoc map-of-data (:item-name next-item) next-item))
>
> Since I was using assoc I was certain I would
> get clojure.lang.PersistentHashMap back, but instead I
> got clojure.lang.PersistentArrayMap.
>
>
>
>
>
>
>
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