On May 11, 2011, at 4:45 PM, Ken Wesson wrote:
> On Wed, May 11, 2011 at 11:04 AM, Chas Emerick <cemer...@snowtide.com> wrote:
>> Somewhat worse from the standpoint of semantic consistency, hinting the var
>> with ^String yields good — yet confusing — results:
>> => (defn ^String foo
>> ([])
>> (^long [a])
>> (^double [a b]))
>> #'user/foo
>> => #(Double. (foo 0 0))
>> #<user$eval2289$fn__2290 user$eval2289$fn__2290@69996e15>
>> => #(String. (foo))
>> #<user$eval2293$fn__2294 user$eval2293$fn__2294@220860ba>
>> And now the var metadata has a :tag, but only for the ^String hint:
>> => (meta #'foo)
>> {:arglists ([] [a] [a b]), :ns #<Namespace user>, :name foo, :line 1, :file
>> "NO_SOURCE_PATH", :tag java.lang.String}
>
> What do you get from (map meta (:arglists (meta #'foo)))?
=> (->> #'foo
meta
:arglists
(map (juxt identity meta)))
([[] nil] [[a] {:tag long}] [[a b] {:tag double}])
Beautiful. I clearly wasn't clever enough to spelunk deeply enough into the
metadataÎ. Thank you, Ken.
I'd hope that the [] arity could get a :tag of java.lang.String, but that may
be running into semantic difficulties as David is potentially pointing out
separately.
Thanks again,
- Chas
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