[Haskell-beginners] compilation error..

[Sunil S Nandihalli]

aah .. Thanks a lot Brandon, you were right .. I was getting a Int and was
destructuring for tuple.. Thanks again
Sunil.

On Thu, Aug 11, 2011 at 5:33 PM, Brandon Allbery <allbery.b at gmail.com>wrote:

> On Thu, Aug 11, 2011 at 07:43, Sunil S Nandihalli <
> sunil.nandihalli at gmail.com> wrote:
>
>> Hello everybody,
>>  when I compile the file
>>
>> https://github.com/sunilnandihalli/is2/blob/master/main.hs
>>
>> I get
>> main.hs:28:64:
>>     Could not deduce (Enum (a, t0))
>>       arising from the arithmetic sequence `0 .. '
>>     from the context (Integral a)
>>       bound by the type signature for
>>                  plotAsString :: Integral a => [(a, a)] -> (a, a) ->
>> String
>>       at main.hs:(26,1)-(38,41)
>>     Possible fix:
>>       add (Enum (a, t0)) to the context of
>>         the type signature for
>>           plotAsString :: Integral a => [(a, a)] -> (a, a) -> String
>>       or add an instance declaration for (Enum (a, t0))
>>     In the second argument of `zip', namely `[0 .. ]'
>>     In the first argument of `M.fromList', namely `(zip locs [0 .. ])'
>>     In the expression: M.fromList (zip locs [0 .. ])
>>
>
> The weird error is because Haskell is defined to promote integer literals
> to instances of Integral, then applying further an instance of Enum; but the
> actual type it's expecting is a tuple because you're using (Just (id,_)) on
> line 34 as the result of (M.lookup).  Were you perhaps expecting
> (M.lookup) to return a tuple of the key and value?
>
> (Also, in light of your previous message, you'll find things compile more
> easily if you learn the correct types and behaviors of standard Haskell
> functions instead of making assumptions possibly based on the behavior of
> some other language.)
>
> --
> brandon s allbery                                      allbery.b at gmail.com
> wandering unix systems administrator (available)     (412) 475-9364 vm/sms
>
>
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