On Fri, Oct 30, 2009 at 11:37 AM, Chouser <chou...@gmail.com> wrote:

> On Fri, Oct 30, 2009 at 11:30 AM, Alex Osborne <a...@meshy.org> wrote:
> >
> > John Harrop wrote:
> >> Was something wrong with this?:
> >>
> >> (defn my-zipmap
> >>   "Returns a map with the keys mapped to the corresponding vals."
> >>   [keys vals]
> >>   (into {} (map vec (partition 2 (interleave keys vals)))))
> >>
> >> :)
> >
> > One reason might be that the original zipmap is 5-10 times faster for
> > large numbers of entries as it doesn't create all the temporary seqs.
>
> Another might be that into, partition and interleave don't exist
> yet when zipmap is defined.


Eh. Implementation details.

That got me to poke in the source for into and:

(def
 #^{:arglists '([coll x] [coll x & xs])
    :doc "conj[oin]. Returns a new collection with the xs
    'added'. (conj nil item) returns (item).  The 'addition' may
    happen at different 'places' depending on the concrete type."}
 conj (fn conj
        ([coll x] (. clojure.lang.RT (conj coll x)))
        ([coll x & xs]
         (if xs
           (recur (conj coll x) (first xs) (next xs))
           (conj coll x)))))

This is especially odd: the two-argument case appears to call itself
recursively to get the argument for a Java call.

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