Ok
but whe the Thompson's book says:
--------------------------------------------
Literals are not overloaded, there is no automatic conversion from Int to Float.
.. we will receive an error message if we type
(floor 5.6) + 6.7
since we are trying to add quantities of two different types. We have to convert
the Int to a Float to perform the addtion, thus:
fromIntegral (floor 5.6) + 6.7
where fromInt takes int to corresponding Float.
--------------------------------------------
pag. 45 "The Craft of Functional Programming" second edition
sadly, if I use a integer number it's work!
5 + 6.7
WHY?????
5 is don't Integer like (floor 5.6)?
--
Alfredo Paz-Valderrama
Sociedad Peruana de Computacion
Mensaje citado por Scott Turner
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.
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