The :- is just a bit of syntax to signify an annotation. As a rule, it goes
*after*
the form you might expect to attach metadata to.
eg. (t/fn [a :- Int] :- Num ....) is [Int -> Num]
(t/let [a :- Int, 1] ...) checks 1 as being under Int.
(t/let [[a b] :- '[Num Num], [1 2]] ...) checks [1 2] as under '[Num
Num], then assigns whatever expression is to the left the type '[Num Num]
(t/for [[a b] :- '[Num Num], foo] :- Ret e) assigns the left hand
side of the binder type '[Num Num], where the right hand side is (U nil
(Seqable '[Num Num])). This is because every iteration [a b] is an element
of foo.
The return type Ret is similarly for one iteration, and the inferred
type will be (Seq Ret).
Thanks,
Ambrose
On Wed, Oct 15, 2014 at 6:34 PM, kurofune <jesseluisd...@gmail.com> wrote:
> Thanks Ambrose,
>
> It makes way better sense after looking at your gist. I still don't
> *quite* understand the :- syntax, though. Is it just introducing a type
> declaration to the data structure that comes after it?
>
> This is a super cool project, by the way.
>
> K
>
>
> On Wednesday, October 15, 2014 3:14:58 PM UTC-5, Ambrose Bonnaire-Sergeant
> wrote:
>>
>> Hi,
>>
>> The issue is that you can't use clojure.core/for in typed code.
>>
>> You must use clojure.core.typed/for
>> <http://www.google.com/url?q=http%3A%2F%2Fclojure.github.io%2Fcore.typed%2F%23clojure.core.typed%2Ffor&sa=D&sntz=1&usg=AFQjCNHQ7AqglYarx-OVAqx1sUXcO4c9vw>,
>> and annotate the parameters and expected type.
>>
>> (ann map-span (All [x y y1] [(Map x y) [y -> y1] -> (Map x y1)]))
>> (defn map-span [m f]
>> (into {} (t/for [[k v] :- '[x y] m] :- '[x y1]
>> [k (f v)])))
>>
>> Here's a real gist
>> <https://gist.github.com/frenchy64/176fa8aadfd5b0cbfc09>.
>>
>> Thanks,
>> Ambrose
>>
>> On Wed, Oct 15, 2014 at 2:28 PM, kurofune <jessel...@gmail.com> wrote:
>>
>>> Hi everyone,
>>>
>>> I am learning core.typed and ran into a stumbling block. When I use
>>> annotations on normal functions and run 'check-ns', things work out ok,
>>>
>>> ;; works as expected
>>>> (ann plus1 [Number -> Number])
>>>> (defn plus1 [n] (+ n 1))
>>>>
>>>> ;; Works as expected
>>>> (ann mult-arity [Number String -> (HMap :mandatory {:a Number :b
>>>> String})])
>>>> (defn mult-arity [n s] {:a n :b s})
>>>
>>>
>>>
>>> but with functions that use destructuring in their body, I run into
>>> problems.
>>>
>>>
>>> ;; Does not work.
>>>> (ann map-span [Map Fn -> Map])
>>>> (defn map-span [m f] (into {} (for [[k v] m] [k (f v)])))
>>>>
>>>
>>>
>>> clojure.lang.ExceptionInfo: Type Checker: Found 8 errors :: {:type-error
>>> :top-level-error, :errors (#<ExceptionInfo clojure.lang.ExceptionInfo:
>>> Polymorphic static method clojure.lang.RT/nth could not be applied to
>>> arguments: Polymorphic Variables: x y Domains: (I (CountRange 1) (U (I
>>> (clojure.lang.Seqable x) clojure.lang.Sequential) (Indexed x))) (Val 0) Any
>>> (U nil (I (clojure.lang.Seqable x) clojure.lang.Sequential) (Indexed x))
>>> Int y Arguments: Any (Val 0) nil Ranges: x
>>> (U x y) ...
>>>
>>>
>>> ;; This also throws errors at the repl.
>>>> (cf (fn [m f] (into {} (for [[k v] m] [k (f v)]))) [Map Fn -> Map])
>>>
>>>
>>>
>>>
>>> I have been on the core.typed wiki and googled around but to no avail. I
>>> have also used lighter amounts of destructuring in the function parameters
>>> and run into similar errors. I am having trouble even understanding the
>>> error messages (even after reading the pertinent wiki page) so if someone
>>> could give me some insights on how to do this properly, I would really
>>> appreciate it.
>>>
>>> K
>>>
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