I was suggesting that you could do something like this (although I'm pretty
sure this doesn't work right now):
(s/fdef map
:args (s/cat :f (s/fspec :args (s/+ ::s/any))
:colls (s/* seqable?))
:ret (s/or :seq seqable? :transducer ifn?)
:fn #(if (zero? (count (-> % :args :colls)))
;; transducer
(ifn? (-> % :ret))
;; lazy seq
(and (seqable? (-> % :ret))
(= (count (-> % :args :f :args))
(count (-> % :args :colls))))))
In the map :args, spec the mapping function as well, then use :fn which can
either relate the args and ret of the main function OR relationships
between the args, as I'm doing at the very end. The input to :fn is the
conformed output of the :args and :ret specs.
But like I said, there are several problems with this right now and I need
to discuss more with Rich whether something like this should be possible
(mostly the args fspec is where I'm seeing issues.
On Monday, June 13, 2016 at 7:57:16 PM UTC-5, Alistair Roche wrote:
>
> Oh, I see what you mean now, Leon. Apologies for not reading more closely!
> Yours is a much more interesting puzzle.
>
> Here's an attempt I made
> <https://gist.github.com/atroche/2248efce0dee46a92d021a8bf7e96237>,
> groping towards it using reflection, but I couldn't even get that to work.
> Would be curious to see what the solution is there, and even more so (like
> you) to see if it can be done without reflection.
>
> On 13 June 2016 at 17:21, Leon Grapenthin <[email protected]>
> wrote:
>
>> Thank Alistair, but that does not really address my question. Alex
>> suggested using :fn of fspec to check arity of a higher-order argument.
>>
>> But I could not find a tool to check function arity. Also I doubt :fn is
>> going to work since I'd expect it to be invoked /after/ the call - i. e.
>> the call would fail before the arity check.
>>
>> Note that in your example you can only use spec/generic testing to check
>> arity because you know the argument types. You can't test a generic higher
>> order fn for just arity like this because the generator won't know the
>> correct types to generate.
>>
>>
>> On Monday, June 13, 2016 at 4:00:30 AM UTC+2, Alistair Roche wrote:
>>>
>>> Hi Leon,
>>>
>>> I think you're looking for fspec
>>> <https://clojure.github.io/clojure/branch-master/clojure.spec-api.html#clojure.spec/fspec>,
>>>
>>> unless I'm misunderstanding something. I wrote up an example
>>> <https://gist.github.com/atroche/731f80376985773c60d5e943b38d8052> that
>>> might be helpful.
>>>
>>> @Ryan thanks for starting this thread, and @Alex thanks for responding.
>>> It's been an interesting discussion!
>>>
>>> Cheers,
>>>
>>>
>
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