module Data.Bool.HT.Private where import Data.List as List (find, ) import Data.Maybe as Maybe (fromMaybe, ) {- | @if-then-else@ as function. Example: > if' (even n) "even" $ > if' (isPrime n) "prime" $ > "boring" -} {-# INLINE if' #-} if' :: Bool -> a -> a -> a if' True x _ = x if' False _ y = y {-| The same as 'if'', but the name is chosen such that it can be used for GHC-7.0's rebindable if-then-else syntax. -} {-# INLINE ifThenElse #-} ifThenElse :: Bool -> a -> a -> a ifThenElse = if' {-| From a list of expressions choose the one, whose condition is true. Example: > select "boring" $ > (even n, "even") : > (isPrime n, "prime") : > [] -} {-# INLINE select #-} select, select0, select1 :: a -> [(Bool, a)] -> a select def = maybe def snd . find fst select0 def = fromMaybe def . lookup True select1 = foldr (uncurry if') zipIf :: [Bool] -> [a] -> [a] -> [a] zipIf = zipWith3 if' infixr 1 ?: {- | Like the @?@ operator of the C progamming language. Example: @bool ?: ("yes", "no")@. -} {-# INLINE (?:) #-} (?:) :: Bool -> (a,a) -> a (?:) = uncurry . if' -- precedence below (||) and (&&) infixr 1 `implies` {- | Logical operator for implication. Funnily because of the ordering of 'Bool' it holds @implies == (<=)@. -} {-# INLINE implies #-} implies :: Bool -> Bool -> Bool implies prerequisite conclusion = not prerequisite || conclusion