Hello all,
below is the code for an utility macro. It wraps all public static
functions of a class in closure functions and imports them into the
current namespace. Clojure name will be prefix-'method name'.
Example: (import-static \"foo\" java.lang.Math)
And yes, I saw static import from contrib :) - the difference here is
that my code creates clojure functions that can be passed to other
functions.
This is just an exercise for learning clojure macros, so I would be
very grateful for any comments on the code, suggestions on how to
improve it, etc ...
It is easier to read from bottom and up ...
I have not implemented multimethod support yet, so currently only the
first of overloaded methods will be imported.
Thank you for your help,
Boris
------------------------------------------
;;; some utility funcitons
(defn mk-counter
"returns a function that for each returns a successive integer
for each invocation."
([] (mk-counter 0))
([start]
(let [n (atom start)]
(fn [] (- (swap! n inc) 1)))))
(defn seq-to-multimap
"takes a sequence s of possibly repeating elements
and converts it to a map, where keys are obtained
by applying key-fn to elements of s and values are
sequences of all elements of s with a given key"
[s key-fn]
(reduce
(fn [m el]
(let [key (key-fn el)]
(assoc m key
(conj (m key []) el))))
{} s))
;;; static import helper functions
(def primitive-type-translation { "bool" "Boolean"
"char" "Character"
"long" "Long"
"int" "Integer"
"short" "Short"
"byte" "Byte"
"float" "Float"
"double" "Double"})
(defn resolve-primitive-type [#^String t] (primitive-type-translation
t t))
(defn type-2-symbol
"resolves type name into a symbol, converts primitive types
to boxed types"
[type]
(symbol (resolve-primitive-type (.getCanonicalName type))))
(defn get-ps-methods
"returns all public static methods of a class c"
[c]
(let [methods (.getMethods c)]
(filter #(let [mod (.getModifiers %1)]
(and (java.lang.reflect.Modifier/isStatic mod)
(java.lang.reflect.Modifier/isPublic mod))) methods)))
(defn get-methods-multimap
"returns a multimap of publi static methods of a class c"
[c]
(seq-to-multimap (get-ps-methods c) #(.getName %1)))
(defn make-java-method-symbol
"returns a symbol that corresponds to a fully qualified
name of the java method"
[#^java.lang.reflect.Method method]
(symbol (str
(.. method getDeclaringClass getName)
"/"
(.getName method))))
(defn get-method-args
"returns a java Class[] array of method's argument types"
[method]
(.getParameterTypes method))
(defn mk-param [param count]
"returns clojure expression for the parameter declaration with the
type"
(with-meta (symbol (str "param" count))
{:tag (type-2-symbol param)}))
(defn mk-params-list [method]
"returns clojure expression for the parameter declarations of a
funciton"
(let [c (mk-counter 0)]
(into [] (map #(mk-param %1 (c)) (get-method-args method)))))
(defn mk-call-exp [method]
"returns clojure expression for the function call.
Example: (java.lang.Math/min param0 param1) "
(let [c (mk-counter 0)]
(cons (make-java-method-symbol method)
(map (fn [param] (symbol (str "param" (c))))
(get-method-args method)))))
(defn mk-func-name [prefix method]
(symbol (str prefix "-" (.getName method))))
(defn mk-func-def [prefix method]
`(defn ~(mk-func-name prefix method)
~(mk-params-list method)
~(mk-call-exp method)))
;;; the macro itself
(defmacro import-static
"wraps all public static functions of a class in
closure functions and imports them into the current
namespace. Clojure name will be prefix-'method name'.
Example: (import-static \"foo\" java.lang.Math)
TODO: multimethod support, currently only the first
of overloaded methods will be imported. "
[prefix class]
`(do ~@(map (fn [[name [method & rest]]]
(mk-func-def prefix method))
(get-methods-multimap
(. Class forName (str class))))))
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