[Haskell-cafe] What is an "expected type" ...

[Arne Dehli Halvorsen]

Bulat Ziganshin wrote:
> Hello Kim-Ee,
>
> Sunday, June 28, 2009, 11:52:57 PM, you wrote:
>
> we already had a *long* discussion on this topic. afaik, it's dichotomy
> between type of term itself and type of position where it's used (f.e.
> argument of some function)
>
>
>   
>> Could you suggest a better word pair to describe the dichotomy then?
>> How about 'calculated' vs 'user-imposed' (or even, 'explicitly-
>> signatured')?

How about "'Int' used in '()'-shaped hole"?
"'Int' from usage, '()' from definition of  'foo' could not be reconciled"?

Arne D Halvorsen


>
>   
>> Dan Piponi-2 wrote:
>>     
>>> I really dislike this error message, and I think the terms are
>>> ambiguous. I think the words 'expected' and 'inferred' apply equally
>>> well to the term, and the context in which it has been found. Both of
>>> the incompatible types were 'inferred', and 'unexpected' is a property
>>> of the combination, not a property of one or the other.
>>> --
>>> Dan
>>>
>>> On Sun, Jun 28, 2009 at 8:24 AM, Martijn van
>>> Steenbergen<martijn at van.steenbergen.nl> wrote:
>>>       
>>>> Hi Michael,
>>>>
>>>> michael rice wrote:
>>>>         
>>>>> as opposed to an "inferred type"?
>>>>>           
>>>> Can you deduce from the following example?
>>>>
>>>>         
>>>>> Prelude> let foo = () :: Int
>>>>> <interactive>:1:10:
>>>>>    Couldn't match expected type `Int' against inferred type `()'
>>>>>    In the expression: () :: Int
>>>>>    In the definition of `foo': foo = () :: Int
>>>>>
>>>>>           
>>>> Hope this helps!
>>>>
>>>> Martijn.
>>>>
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>>>       
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