On 2005 April 12 Tuesday 23:12, Alfredo Paz-Valderrama wrote:
If i write this in hugs:
1 / 2
I get 0.5 by answer, but the / operator signature is:
float -> float -> float
1 and 2 are overloaded. They can be Integer, Float, etc. You can think of 2 as meaning (fromInteger 2). FromInteger is defined in the Prelude to convert an Integer to any numeric type. Haskell organizes overloading using type classes. The type class called Num contains fromInteger, +, -, and *. So these operators along with the integer literals 1,2, etc. can be used with any numeric type. You can define your own numeric type (for example polynomials) and use 1,2, and + with that. Actually, the / operator is not limited to Float, either. It is overloaded for the type class "Fractional", which includes Double and Rational. Hugs will tell you the type is Float -> Float -> Float because there's a defaulting mechanism so that if multiple types are possible, Hugs can choose one and give you an answer.