[Haskell-beginners] numerical types, the $ operator

[TG]

Hi all
I'm trying to understand the following simple function

>-- | fractional part of number.
>frac :: (RealFrac a) => a -> a
>frac x = x - fromInteger . floor $ x

which apparently is wrong. Whereas this is ok

>frac x = x - fromInteger (floor x)

Is the 1st one wrong because it is trying to apply the _whole_ 'left of
$' to the 'x' on the right?
How would an experienced guy write this without parentheses?


Moreover, I've put the 'RealFrac' by looking at ":t floor".
What kind of class constraint whould you put for doing eg:

>frac x = x - fromInteger (floor (sqrt x) )

since 'floor' takes fractional and 'sqrt' takes RealFrac? Some kind of
super-class?
Thank you.

PS
Seems that types are half the language, if not more ..


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  TG
  cowscanfly at airpost.net

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