2 Sep
2010
2 Sep
'10
8:53 a.m.
On Thursday 02 September 2010 14:49:12, Eoin C. Bairéad wrote:
Example 2
Prelude> let fac n = if n == 0 then 1 else n * fac (n-1)
How does it know to stop ?
It tests for n == 0. If that returns True, the recursion stops.
and why does fac 2.5 hang?
Because 2.5 is not an integer, so fac gets called with 2.5 1.5 0.5 -0.5 -1.5 -2.5 ... but never with 0, so you get infinite recursion.