Is there a difference between floor and truncate in Haskell

Question

Does there exist a difference in functionality between floor and truncate in Haskell?

They seem to perform the same functionality and they have the same type signature:

• truncate :: (Integral b, RealFrac a) => a -> b
• floor :: (Integral b, RealFrac a) => a -> b

Answer 1

Yes, for negative numbers. If we read the documentation, we see:

truncate :: Integral b => a -> b

truncate x returns the integer nearest x between zero and x

and:

floor :: Integral b => a -> b

floor x returns the greatest integer not greater than x

So if we enter a negative number, like -3.5 we obtain:

Prelude> truncate (-3.5)
-3
Prelude> floor (-3.5)
-4