[Haskell-cafe] Unresolved overloading error
Lennart Augustsson
lennart at augustsson.net
Sat Mar 31 05:25:19 EDT 2007
Actually, I don't know what type you want p to be, so you might not
need the fromIntegral.
On Mar 31, 2007, at 10:21 , Lennart Augustsson wrote:
> The definition of fac forces the result to have the same type as
> the argument.
> Then in binom you use / which forces the type to be Fractional.
> And finally you use ^ which forces the type to be Integral.
> There is no type that is both Fractional and Integral.
>
> I suggest using div instead of / in binom (binomial coefficients
> are integers after all).
> And then a fromIntegral applied to the binom call in bernoulli.
>
> -- Lennart
>
> On Mar 31, 2007, at 10:04 , Scott Brown wrote:
>
>> I have written this code in Haskell which gives an unresolved
>> overloading error.
>> The function bernoulli should give the probability of j successes
>> occuring in n trials, if each trial has a probability of p.
>>
>> > fac 0 = 1
>> > fac n = n * fac(n - 1)
>>
>> > binom n j = (fac n)/((fac j)*(fac (n - j)))
>>
>> > bernoulli n p j = (binom n j)*(p ^ j) * ((1 - p)^(n - j))
>>
>> However, bernoulli 6 0.5 3 gives the error:
>>
>> ERROR - Unresolved overloading
>> *** Type : (Fractional a, Integral a) => a
>> *** Expression : bernoulli 6 0.5 3
>>
>> Why doesn't Haskell infer the types? What kind of type casting or
>> type definition can I use to fix the error?
>> Send instant messages to your online friends http://
>> au.messenger.yahoo.com
>>
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