How to return float number with 2 digits after decimal point?

Question

I have some simple function

f :: Float -> Float
f x = x

Prelude> f 5.00
5.0

Why not 5.00? How can I achieve this?

Answer 1

If you want something from base then use showGFloat:

 > import Numeric
 > showGFloat (Just 2) 1.99438 ""
 "1.99"
 > :t showGFloat
 showGFloat :: RealFloat a => Maybe Int -> a -> ShowS