Ternary operator: Difference between revisions
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== Further reading == | == Further reading == | ||
* | * {{GHCUsersGuide|exts/rebindable_syntax||a section on Rebindable Syntax}} | ||
* [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] | ||
[[Category:Code]] | [[Category:Code]] | ||
[[Category:Idioms]] | [[Category:Idioms]] | ||
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"