On Nov 16, 4:28 pm, Chouser <chou...@gmail.com> wrote:
> 'let' is also careful to always have the user provide the symbol
> being bound as a symbol. That is you say {:keys [a b c]} not
> {:keys [:a :b :c]}. What do you think of having let-kw take
> symbols instead of keywords for the names being bound?
I think that's a good idea.
Updated version:
(defmacro let-kw
"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 let-kw as symbols, with default values either
specified in the keyword spec or nil. Keyword specs may consist of
just the bare keyword symbol, which defaults to nil, or may have
the general form [keyword-name keyword-default-value*
keyword-supplied?*]. keyword-supplied? 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)
symbols (map first kw-spec)
keywords (map (comp keyword name) symbols)
defaults (map second kw-spec)
destrmap {:keys (vec symbols) :or (zipmap 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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