user> (use 'clojure.contrib.def) nil user> (defnk f [:b 43] (inc b)) #'user/f user> (f) 44 user> (f :b 100) 101 user=> (defnk with-positional [foo :b 43] (+ foo (inc b))) #'user/with-positional user=> (with-positional 5 :b 1) 7
Source
clojure/contrib/def.clj:122
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(defmacro defnk
"Define a function accepting keyword arguments. Symbols up to the first
keyword in the parameter list are taken as positional arguments. Then
an alternating sequence of keywords and defaults values is expected. The
values of the keyword arguments are available in the function body by
virtue of the symbol corresponding to the keyword (cf. :keys destructuring).
defnk accepts an optional docstring as well as an optional metadata map."
[fn-name & fn-tail]
(let [[fn-name [args & body]] (name-with-attributes fn-name fn-tail)
[pos kw-vals] (split-with symbol? args)
syms (map #(-> % name symbol) (take-nth 2 kw-vals))
values (take-nth 2 (rest kw-vals))
sym-vals (apply hash-map (interleave syms values))
de-map {:keys (vec syms)
:or sym-vals}]
`(defn ~fn-name
[~@pos & options#]
(let [~de-map (apply hash-map options#)]
~@body))))
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