[Agda] a strange "unsolved" report

[mechvel at scico.botik.ru]

On 2020-10-04 23:30, James Wood wrote:
> Hi Sergei,
> 
> Quick questions first: is `_∷_` overloaded at all in this context?
> That'd be my guess for why Agda has no clue what the type is supposed 
> to be.
> 

It is overloaded.
But there are other similar assignments before and around (like the one 
marked with *),
and Agda does resolve them without providing a signature.

--
SM



> On 04/10/2020 18:19, mechvel at scico.botik.ru wrote:
>> Dear Agda developers,
>> 
>> There is a question about the following code fragment:
>> 
>> -----------------------------------------------------
>> +ms-assoc-aux {monᶜ a e ∷ mons} {monᶜ b e' ∷ mons'} {monᶜ c e'' ∷
>> mons''} ... =
>> 
>>     aux (<-cmp e e') (<-cmp e' e'') (<-cmp e e'')
>>     where
>>     m = monᶜ a e;  m' = monᶜ b e';   m'' = monᶜ c e''
>> 
>>     mmons = m ∷ mons                 -- *
>> 
>>     -- m'mons' : List Mon            -- (I-s)
>>     m'mons' = m' ∷ mons'             -- (I)
>> 
>>     m''mons'' = m'' ∷ mons''
>>     ...
>> -----------------------------------------------------
>> 
>> Agda 2.6.1 reports
>> "
>> Sort _1156  [ at ...Over-abelianGroup.agda:414,5-12 ]
>> _1157 : _1156  [ at ...Over-abelianGroup.agda:414,5-12 ]
>> _1159 : _1157  [ at ...Over-abelianGroup.agda:414,15-25 ]
>> "
>> 
>> I guess this is the kind of "unsolved metas".
>> And the first "unsolved" is about the line marked (I).
>> 
>> The previous line (marked *) is solved - while it is not any more 
>> clear
>> than (I).
>> 
>> Then, after adding the signature (I-s), everything is type-checked.
>> 1) This necessity to add signature in the middle of an array of short
>> assignments of the same
>>    type looks strange.
>> 2) There are many similar fragments in the program, and I never 
>> observed
>> such an effect.
>> 
>> What might this mean?
>> 
>> --
>> SM
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