Re: [Haskell-cafe] First questions!

Hi! 2010/9/2 Eoin C. Bairéad

Example 2

Prelude> let fac n = if n == 0 then 1 else n * fac (n-1)

How does it know to stop ?

When fac is called with n=0 it returns 1 and stops the recursion.

and why does fac 2.5 hang?

fac, as you defined it, is only defined for integers. As you repeatedly subtract 1 from n you will never get to 0 (you will get to 0.5 and then -0.5) and thus the recursion will never terminate.\