[Haskell-cafe] Mis-understanding something in Haskell interpretation

[J. Garrett Morris]

On 10/3/06, Edward Ing <inge at ihitacow.com> wrote:
> The source is below. Side is types as Float. My assumption was that
> Haskell would know how to convert the Int to a float and all would be
> well. I am I mistaken somewhere? The problem is with the last line.

Yes - Haskell does not automatically promote numeric types.  In this
case, the following code compiles:

vertex :: Vertex -> Int -> Int -> Side -> Vertex
vertex (a ,b) currentSide totalSides length  =
       let  angle  = (360 / fromIntegral totalSides) *  fromIntegral
currentSide  in
               ( a  + ( length * (sin  angle)), b + ( (*) (cos angle) length ) )

although I'm not sure it's exactly what you want.

 /g