Why such implementation of partial in clojure.core -


i stumbled across implementation of partial function in cojure.core. looks this:

(defn partial   "takes function f , fewer normal arguments f, ,   returns fn takes variable number of additional args. when   called, returned function calls f args + additional args."   {:added "1.0"    :static true}   ([f] f)   ([f arg1]    (fn [& args] (apply f arg1 args)))   ([f arg1 arg2]    (fn [& args] (apply f arg1 arg2 args)))   ([f arg1 arg2 arg3]    (fn [& args] (apply f arg1 arg2 arg3 args)))   ([f arg1 arg2 arg3 & more]    (fn [& args] (apply f arg1 arg2 arg3 (concat more args)))))

why has several parity options if have one? performance optimisation concat doesn't called in cases?

i mean otherwise, right? 

(defn partial   ([f] f)   ([f & more]    (fn [& args] (apply f (concat more args))))   )

i noticed several other functions follow same pattern.

yes, it's performance optimization.

i'ts not not calling concat - it's fact & in argument list requires collection created well. clojure core libraries tend take performance seriously, under assumption basic building blocks of language present in everyone's performance bottleneck.


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