[Haskell-cafe] Trivial question... solve_qe
robert dockins
robdockins at fastmail.fm
Wed Jun 15 10:45:42 EDT 2005
> So, in a word: I need a tutorial for dummies
I don't know of any tutorials like you have described. Perhaps someone
else does?
> Now, my current problem is: my program for solving quadratic equation
> won't compile...
You left out some 'Just' constructors.
import System
solve_qe :: Maybe (Double, Double, Double) -> Maybe (Double, Double)
solve_qe Nothing = Nothing
--solve_qe (a, b, c)
solve_qe (Just (a, b, c))
| d >= 0 = Just ((-b + (sqrt d)) / (2 * a), (-b - (sqrt d)) / (2 * a))
| otherwise = Nothing
where d = b^2 - 4*a*c
evalArgs :: [String] -> Maybe (Double, Double, Double)
--evalArgs (a:b:c:[]) = (read a, read b, read c)
evalArgs (a:b:c:[]) = Just (read a, read b, read c)
evalArgs _ = Nothing
main = do
args <- getArgs
print (solve_qe (evalArgs args))
More information about the Haskell-Cafe
mailing list