Looks like Google Groups posting software forced line wraps at less
than 80 columns, breaking the code. Lovely. Here's the fn-keywords
macro reformatted for 72 column wrapping.
(defmacro fn-keywords
"Adds flexible keyword handling to any form which has a
parameter list: fn, defn, defmethod, letfn, and
others. Keywords may be passed to the surrounding form as &
rest arguments, lists, or maps. Lists or maps must be used for
functions with multiple arities if more than one arity has
keyword parameters. Keywords are bound inside fn-keywords as
symbols, with default values either specified in the keyword
spec or nil. Keyword specs may consist of just the bare
keyword, which defaults to nil, or may have the general form
[:keyword-name keyword-default-value*
keyword-bound?*]. keyword-bound? is an optional symbol bound
to true if the keyword was supplied, and to false otherwise."
[kw-spec-raw kw-args & body]
(let [kw-spec (map #(if (sequential? %) % [%]) kw-spec-raw)
keywords (map first kw-spec)
symbols (map (comp symbol name) keywords)
defaults (map second kw-spec)
destrmap {:keys (vec symbols)
:or (apply hash-map
(interleave symbols defaults))}
supplied (reduce (fn [m [k v]] (assoc m k v)) (sorted-map)
(remove (fn [[_ val]] (nil? val))
(partition 2
(interleave
keywords
(map (comp second rest)
kw-spec)))))
kw-args-map (gensym)]
`(let [kw-args# ~kw-args
~kw-args-map (if (map? kw-args#)
kw-args#
(apply hash-map kw-args#))
~destrmap ~kw-args-map]
~@(if (empty? supplied)
body
`((apply (fn [~@(vals supplied)]
~...@body)
(map (fn [x#] (contains? ~kw-args-map x#))
[~@(keys supplied)])))))))
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