It might help thinking in terms of Java interfaces, Foo and Bar.
(definterface Foo
(foo []))
(definterface Bar
(bar []))
(I Foo Bar) is a value that extends both Foo and Bar.
(deftype IImp []
Foo
(foo [this])
Bar
(bar [this]))
(->IImp) is of type Foo, Bar, (I Foo Bar) and (U Foo Bar).
Assuming we assign (->IImp) the type (I Foo Bar), we can call these safely:
(let [i :- (I Foo Bar), (->IImp)]
(.foo i)
(.bar i))
A type that just implements Foo is not a Bar, so we can't claim it's a Foo
*and* a Bar.
(deftype UImp []
Foo
(foo [this]))
(->UImp) is of type Foo, and (U Foo Bar).
Assuming we assign (->UImp) the type (U Foo Bar), the same operations now
must cast at runtime.
(let [i :- (U Foo Bar), (->UImp)]
(if (instance? Foo)
(.foo i)
(.bar i))
Thanks,
Ambrose
On Thu, Apr 16, 2015 at 5:15 PM, Sven Richter <sver...@googlemail.com>
wrote:
> I meant when I change:
>
> (t/HVec [Keyword (t/U Keyword (t/HVec [Keyword Number])) t/Any t/Any *])
> to (t/HVec [Keyword (t/I Keyword (t/HVec [Keyword Number])) t/Any t/Any *])
>
> ^^
> to ^^
> Still I think that making an intersection of it is wrong conceptually.
>
>
> Thanks,
> Sven
>
> Am Donnerstag, 16. April 2015 23:08:30 UTC+2 schrieb Ambrose
> Bonnaire-Sergeant:
>>
>> I don't see an intersection, what do you mean?
>>
>> Thanks,
>> Ambrose
>>
>> On Thu, Apr 16, 2015 at 4:43 PM, Sven Richter <sve...@googlemail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I tried both destructuring and the nth form instead of second and first.
>>> None of which worked.
>>>
>>> However, if I change the Union to Intersection in
>>>
>>> (t/HVec [Keyword (t/U Keyword (t/HVec [Keyword Number])) t/Any t/Any *])
>>>
>>> it works for the definition of the multimethod. Does that make sense? I
>>> thought Union was either one type or the other.
>>>
>>> Thanks,
>>> Sven
>>>
>>>
>>> Am Donnerstag, 16. April 2015 21:44:25 UTC+2 schrieb Ambrose
>>> Bonnaire-Sergeant:
>>>>
>>>> I don't think second's type is is smart enough.
>>>>
>>>> Try using nth or destructuring instead:
>>>>
>>>> (let [[f s] v]
>>>> (if (vector? s) (first s) s))
>>>>
>>>> or
>>>>
>>>> (if (vector? (nth v 1)) (first (nth v 1)) s)
>>>>
>>>> Thanks,
>>>> Ambrose
>>>>
>>>> On Thu, Apr 16, 2015 at 3:39 PM, Sven Richter <sve...@googlemail.com>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I have this code:
>>>>>
>>>>> (defalias html-label (t/HVec [Keyword (t/HMap :mandatory {:for String}
>>>>> ) String]))
>>>>> (defalias html-form (t/HVec [Keyword (t/HMap :mandatory {:id String})
>>>>> t/Any *]))
>>>>> (defalias html-form-group (t/HVec [html-label html-form]))
>>>>>
>>>>> (t/ann dt->hiccup [(HVec [Keyword (U Keyword (HVec [Keyword Number]))
>>>>> t/Any t/Any *]) ->
>>>>> html-form-group])
>>>>> (defmulti dt->hiccup (t/fn [col :- pt/et-column]
>>>>> (if (vector? (second col))
>>>>> (first (second col))
>>>>> (second col))))
>>>>>
>>>>> And here comes the error message when checking this function:
>>>>>
>>>>> Type Error (leiningen/td_to_hiccup.clj:25:34) Polymorphic function
>>>>> first could not be applied to arguments:
>>>>> Polymorphic Variables:
>>>>> x
>>>>>
>>>>> Domains:
>>>>> (t/HSequential [x t/Any *])
>>>>> (t/Option (t/EmptySeqable x))
>>>>> (t/NonEmptySeqable x)
>>>>> (t/Option (clojure.lang.Seqable x))
>>>>>
>>>>> Arguments:
>>>>> (t/U Keyword (t/HVec [clojure.lang.Keyword java.lang.Number]))
>>>>>
>>>>> Ranges:
>>>>> x :object {:path [(Nth 0)], :id 0}
>>>>> nil
>>>>> x
>>>>> (t/Option x)
>>>>>
>>>>> in: (first (second col))
>>>>> in: (first (second col))
>>>>>
>>>>>
>>>>> ExceptionInfo Type Checker: Found 1 error clojure.core/ex-info (core.
>>>>> clj:4403)
>>>>>
>>>>> My assumption is that the check (if (vector? (second col will return
>>>>> only true if it is this type: (HVec [Keyword Number]). However, I
>>>>> have the impression that core.typed does not resolve the if expression
>>>>> properly.
>>>>> Or maybe I am missing something completely.
>>>>>
>>>>> Any hints or recommendations?
>>>>>
>>>>> Thanks,
>>>>> Sven
>>>>>
>>>>>
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