Difference between revisions of "Ternary operator"
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DonStewart (talk | contribs) (ternary operator idea) |
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</haskell> |
</haskell> |
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+ | Another version that works in GHC. |
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+ | |||
+ | <haskell> |
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+ | data Cond a = a :? a |
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+ | |||
+ | infixl 0 ? |
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+ | infixl 1 :? |
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+ | |||
+ | (?) :: Bool -> Cond a -> a |
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+ | True ? (x :? _) = x |
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+ | False ? (_ :? y) = y |
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+ | |||
+ | test = 1 < 2 ? "Yes" :? "No" |
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+ | </haskell> |
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== Further reading == |
== Further reading == |
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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"