On Fri, Dec 5, 2008 at 9:22 AM, Randall R Schulz <[EMAIL PROTECTED]> wrote:
>
> On Thursday 04 December 2008 23:23, Meikel Brandmeyer wrote:
>> Hi,
>>
>> On 5 Dez., 00:38, Randall R Schulz <[EMAIL PROTECTED]> wrote:
>>
>> > And am I mistaken in my reading of the API docs for (defmulti ...)
>> > and (defmethod ...) or is there no accommodation in either for
>> > doc-strings? Surely that's not the case, right?
>>
>> You can always use:
>>
>> (defmulti #^{:arglists '([a b] [a b c]) :doc "bla"} foo identity)
>
> Why all the circumlocutions to bring a multimethod up to the level of
> documentation support of a plain function?
Attached is a patch that adds doc-string and metadata support to
defmulti. It does not generate arglists metadata automatically like
defn does since the arglists are not supplied in the defmulti form as
they are in defn. One possibility would be to see if the dispatch
function has an :arglists entry in its metadata and use that if it
does, but I did not include that here since it opens up the
possibility that the :arglists and :doc entries could get out of sync.
Below is a sample usage of the new doc-string support. I'd be
interested to hear people's thoughts.
Regards,
- J.
kant[~/src/clojure]$ iclj
1:1 user=> (defmulti fib "Calculates the nth value of the fib sequence"
{:arglists '([n])}
int)
#'user/fib
1:3 user=> (defmethod fib 0 [_] 0)
#<MultiFn [EMAIL PROTECTED]>
1:4 user=> (defmethod fib 1 [_] 1)
#<MultiFn [EMAIL PROTECTED]>
1:5 user=> (defmethod fib :default [n] (+ (fib (- n 2)) (fib (- n 1))))
#<MultiFn [EMAIL PROTECTED]>
1:6 user=> (map fib (range 10))
(0 1 1 2 3 5 8 13 21 34)
1:7 user=> (doc fib)
-------------------------
user/fib
([n])
Calculates the nth value of the fib sequence
nil
1:8 user=> (meta (var fib))
{:line 1, :file "repl-1", :doc "Calculates the nth value of the fib
sequence", :arglists ([n]), :tag clojure.lang.MultiFn, :name fib, :ns
#<Namespace user>}
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Index: src/clj/clojure/core.clj
===================================================================
--- src/clj/clojure/core.clj (revision 1147)
+++ src/clj/clojure/core.clj (working copy)
@@ -175,26 +175,37 @@
(recur (conj ret (first s)) (rest s))
(seq ret)))))
-(def
+(def
+ #^{:private true
+ :arglists '([fdecl])
+ :doc "Extracts optional doc string and attr-maps from function
+ declarations. Returns a vector containing the attr-map and the
+ rest of the function declaration."}
+ extract-attrs (fn extract-attrs [fdecl]
+ (let [m (if (string? (first fdecl))
+ {:doc (first fdecl)}
+ {})
+ fdecl (if (string? (first fdecl))
+ (rest fdecl)
+ fdecl)
+ m (if (map? (first fdecl))
+ (conj m (first fdecl))
+ m)
+ fdecl (if (map? (first fdecl))
+ (rest fdecl)
+ fdecl)]
+ [m fdecl])))
+(def
#^{:doc "Same as (def name (fn [params* ] exprs*)) or (def
name (fn ([params* ] exprs*)+)) with any doc-string or attrs added
to the var metadata"
:arglists '([name doc-string? attr-map? [params*] body]
[name doc-string? attr-map? ([params*] body)+ attr-map?])}
defn (fn defn [name & fdecl]
- (let [m (if (string? (first fdecl))
- {:doc (first fdecl)}
- {})
- fdecl (if (string? (first fdecl))
- (rest fdecl)
- fdecl)
- m (if (map? (first fdecl))
- (conj m (first fdecl))
- m)
- fdecl (if (map? (first fdecl))
- (rest fdecl)
- fdecl)
+ (let [fdecl (extract-attrs fdecl)
+ m (first fdecl)
+ fdecl (second fdecl)
fdecl (if (vector? (first fdecl))
(list fdecl)
fdecl)
@@ -986,16 +997,28 @@
([x form & more] `(-> (-> ~x ~form) [EMAIL PROTECTED])))
;;multimethods
-(defmacro defmulti
+(defmacro
+ defmulti
"Creates a new multimethod with the associated dispatch function. If
default-dispatch-val is supplied it becomes the default dispatch
value of the multimethod, otherwise the default dispatch value
is :default."
- ([name dispatch-fn] `(defmulti ~name ~dispatch-fn :default))
- ([name dispatch-fn default-val]
- `(def ~(with-meta name (assoc ^name :tag 'clojure.lang.MultiFn))
- (new clojure.lang.MultiFn ~dispatch-fn ~default-val))))
+ ([name & fdecl]
+ (let [args (extract-attrs fdecl)
+ m (first args)
+ args (second args)
+ dispatch-fn (first args)
+ default-val (or (second args) :default)]
+ `(def ~(with-meta name
+ (conj (assoc ^name :tag 'clojure.lang.MultiFn) m))
+ (new clojure.lang.MultiFn ~dispatch-fn ~default-val)))))
+(.setMeta
+ (var defmulti)
+ (conj (meta (var defmulti))
+ {:arglists '([name doc-string? attr-map? dispatch-fn]
+ [name doc-string? attr-map? dispatch-fn default-val])}))
+
(defmacro defmethod
"Creates and installs a new method of multimethod associated with dispatch-value. "
[multifn dispatch-val & fn-tail]
