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

Bulat Ziganshin bulat.ziganshin at gmail.com
Sun Jun 28 15:58:56 EDT 2009


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')?



> 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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>> 




-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com



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