Ternary operator: Difference between revisions
DonStewart (talk | contribs) ternary operator idea |
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</haskell> | </haskell> | ||
Another version that works in GHC. | |||
<haskell> | |||
data Cond a = a :? a | |||
infixl 0 ? | |||
infixl 1 :? | |||
(?) :: Bool -> Cond a -> a | |||
True ? (x :? _) = x | |||
False ? (_ :? y) = y | |||
test = 1 < 2 ? "Yes" :? "No" | |||
</haskell> | |||
== Further reading == | == Further reading == | ||
Revision as of 11:01, 16 November 2008
With a bit of work, we can define a ternary conditional operator in Haskell. Courtesy of Andrew Baumann. This appears only to be valid in Hugs?
import qualified Prelude
data Cond a = a : a
infixl 0 ?
infixl 1 :
(?) :: Prelude.Bool -> Cond a -> a
Prelude.True ? (x : _) = x
Prelude.False ? (_ : y) = y
test = 1 Prelude.< 2 ? "yeah" : "no!"Another version that works in GHC.
data Cond a = a :? a
infixl 0 ?
infixl 1 :?
(?) :: Bool -> Cond a -> a
True ? (x :? _) = x
False ? (_ :? y) = y
test = 1 < 2 ? "Yes" :? "No"