[Haskell-cafe] testing for exceptions
Roelof Wobben
r.wobben at home.nl
Sat Oct 31 10:16:06 UTC 2015
Hello,
I have made this exercise which can be found at the Craft of Functional
Programming book.
-- exercise 32
-- Suppose we have to raise 2 to the power n. If n is even, 2*m say, then
-- 2n = 22*m = (2m)2
-- If n is odd, 2*m+l say, then
-- 2n = 22*m+l = (2n)2*2
-- Give a recursive function to compute 2n which uses these insights.
f2 :: Integer -> Integer
f2 n
| n < 0 = error "This will only run for positive numbers"
| n == 0 = 1
| even n = f2 ( n `div` 2) ^ 2
| odd n = (f2 ( n `div` 2) ^ 2) * 2
Now I have to make Hunit tests for it,
But is there a way I can test if the error message is shown when a
negative number is being used ?
Roelof
More information about the Haskell-Cafe
mailing list