On Oct 17, 2006, at 1:37 PM, Víctor A. Rodríguez wrote:
What's wrong with doing it this way?
-- ** UNTESTED CODE **
verifyAdd :: Int -> Int -> Int -> Bool verifyAdd a b sum | a + b == sum = True otherwise = False
testAddMundane :: Int -> Int -> Bool testAddMundane a b = verifyAdd a b (a + b)
-- all the IO-dependent stuff is below this line --
testAddRandom :: IO Bool testAddRandom = do a <- randomIO b <- randomIO return verifyAdd a b (a + b)
I discovered something worst yet :-P Using the next code and calling verifyAdd or testAddMundane it says :
Program error: verifyAdd: ERROR
Instead calling testAddRandom only says :
:: IO Bool (55 reductions, 92 cells)
This is due to the magic of lazy evaluation. You never use the result of 'testAddRandom', so it's never evaluated, which means your call to 'error' is also never evaluated. Type: testAddRandom >>= print on the command line and you should get the same error, because the call to 'print' demands the result of running testAddRandom.
---- CODE STARTS HERE, AND IS TESTED -----
import Random
verifyAdd :: Int -> Int -> Int -> Bool verifyAdd a b sum = error "verifyAdd: ERROR"
testAddMundane :: Int -> Int -> Bool testAddMundane a b = verifyAdd a b (a + b)
-- all the IO-dependent stuff is below this line --
testAddRandom :: IO Bool testAddRandom = do a <- randomIO b <- randomIO return ( verifyAdd a b (a+b) )
-- Víctor A. Rodríguez (http://www.bit-man.com.ar) El bit Fantasma (Bit-Man) Perl Mongers Capital Federal (http://cafe.pm.org/) GNU/Linux User Group - FCEyN - UBA (http://glugcen.dc.uba.ar/)
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