Difference between revisions of "Ternary operator"
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(→Further reading: fix user guide link) |
(→Further reading: rebindable syntax in the ghc users guide) |
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== Further reading == |
== Further reading == |
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| + | * {{GHCUsersGuide|exts/rebindable_syntax||a section on Rebindable Syntax}} |
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| − | * [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#extension-RebindableSyntax Rebindable syntax] |
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* [http://www.eecs.usma.edu/webs/people/okasaki/pubs.html#hw02 Techniques for Embedding Postfix Languages in Haskell] |
* [http://www.eecs.usma.edu/webs/people/okasaki/pubs.html#hw02 Techniques for Embedding Postfix Languages in Haskell] |
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Revision as of 23:07, 24 July 2021
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"