data Day = Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday deriving (Eq, Ord, Show, Read, Bounded, Enum) -- *Main> Wednesday -- Wednesday -- *Main> show Wednesday -- "Wednesday" -- *Main> read "Saturday" :: Day -- Saturday -- *Main> Saturday == Sunday -- False -- *Main> Saturday == Saturday -- True -- *Main> Saturday > Friday -- True -- *Main> Monday `compare` Wednesday -- LT -- *Main> minBound :: Day -- Monday -- *Main> maxBound :: Day -- Sunday -- *Main> succ Monday -- Tuesday -- *Main> pred Saturday -- Friday -- *Main> pred Monday -- *** Exception: pred{Day}: tried to take `pred' of first tag in enumeration -- *Main> pred Sunday -- Saturday -- *Main> [Thursday .. Sunday] -- [Thursday,Friday,Saturday,Sunday] -- *Main> [minBound .. maxBound] :: [Day] -- [Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday] -- *Main> [minBound .. maxBound] -- <interactive>:50:2: -- Ambiguous type variable `t0' in the constraints: -- (Bounded t0) -- arising from a use of `minBound' at <interactive>:50:2-9 -- (Enum t0) -- arising from the arithmetic sequence `minBound .. maxBound' -- at <interactive>:50:1-22 -- Probable fix: add a type signature that fixes these type variable(s) -- In the expression: minBound -- In the expression: [minBound .. maxBound] -- In an equation for `it': it = [minBound .. maxBound]
