[Haskell-cafe] Mixed-type arithmetic, or type coercion

[Neil Mitchell]

Hi

> Arithmetic operators in haskell appear to require their operands to
> have the same type.  How can I do arithmetic between operands of
> different types?

You probably don't want to.


> Alternatively, how do I coerce a value from being an Int to being a Double?

You ask Hoogle:

http://haskell.org/hoogle/?q=Integer+-%3E+Double

The answer is fromInteger/toInteger as required.

> calc :: Int -> Double -> Double
> calc count weight = fromInteger (toInteger count) * weight

toInteger promotes the Int to an Integer, fromInteger then converts
that to a Double.

Thanks

Neil