Safe Haskell	Safe-Inferred
Language	Haskell2010

Data.Predicate

Contents

Predicate
Result
Product

Synopsis

Predicate

type Predicate a f t = a -> Result f t Source

A predicate is a function of some value of type a to a Result, i.e. a Bool-like value with Okay as True and Fail as False, which carries additional data in each branch.

constant :: t -> Predicate a f t Source

A predicate which always returns Okay with the given value as metadata.

failure :: f -> Predicate a f t Source

A predicate which always returns Fail with the given value as metadata.

true :: Predicate a f () Source

false :: Predicate a () t Source

and :: Predicate a f t -> Predicate a f t' -> Predicate a f (t ::: t') Source

A predicate corresponding to the logical AND connective of two predicate.

or :: Predicate a f t -> Predicate a f t -> Predicate a f t Source

A predicate corresponding to the logical OR connective of two predicates. It requires the metadata of each Okay branch to be of the same type.

If both arguments evaluate to Okay the one with the smaller "delta" will be preferred, or--if equal--the left-hand argument.

orElse :: Predicate a f t -> Predicate a f t' -> Predicate a f (Either t t') Source

A predicate corresponding to the logical OR connective of two predicates. The metadata of each Okay branch can be of different types.

If both arguments evaluate to Okay the one with the smaller "delta" will be preferred, or--if equal--the left-hand argument.

(.&.) :: Predicate a f t -> Predicate a f t' -> Predicate a f (t ::: t') infixr 3 Source

Alias of and.

(.|.) :: Predicate a f t -> Predicate a f t -> Predicate a f t infixr 2 Source

Alias of or.

(|||) :: Predicate a f t -> Predicate a f t' -> Predicate a f (Either t t') infixr 2 Source

Alias of orElse.

opt :: Predicate a f t -> Predicate a f (Maybe t) Source

A predicate modifier which makes the given predicate optional, i.e. the Okay metadata type becomes a Maybe and in the failure-case Nothing is returned.

def :: t -> Predicate a f t -> Predicate a f t Source

A predicate modifier which returns as Okay metadata the provided default value if the given predicate fails.

mapOkay :: (t -> Result f t') -> Predicate a f t -> Predicate a f t' Source

Like fmap, but only maps the Okay metadata to another result.

mapFail :: (f -> Result f' t) -> Predicate a f t -> Predicate a f' t Source

Like mapOkay, but for the Fail case.

exec :: Predicate a f t -> a -> (f -> b) -> (t -> b) -> b Source

Result

data Result f t Source

A Bool-like type where each branch--Fail and Okay--carries some metadata.

Constructors

Fail f
Okay !Double t

Instances

Monad (Result f)
Functor (Result f)
Applicative (Result f)
(Eq f, Eq t) => Eq (Result f t)
(Ord f, Ord t) => Ord (Result f t)
(Show f, Show t) => Show (Result f t)

result :: (f -> a) -> (Double -> t -> a) -> Result f t -> a Source

fromEither :: Either f t -> Result f t Source

toEither :: Result f t -> Either f t Source

newtype ResultT f m t Source

Constructors

ResultT
Fields runResultT :: m (Result f t)

Instances

MonadTrans (ResultT f)
Monad m => Monad (ResultT f m)
Monad m => Functor (ResultT f m)
Monad m => Applicative (ResultT f m)
MonadIO m => MonadIO (ResultT f m)

resultT :: Monad m => (f -> m a) -> (Double -> t -> m a) -> ResultT f m t -> m a Source

resultT' :: Monad m => (f -> m a) -> (t -> m a) -> ResultT f m t -> m a Source

mapResultT :: (m (Result f t) -> n (Result f' t')) -> ResultT f m t -> ResultT f' n t' Source

hoistResult :: Monad m => Result f t -> ResultT f m t Source

okay :: Monad m => Double -> t -> ResultT f m t Source

throwF :: Monad m => f -> ResultT f m t Source

Product

data a ::: b infixr 5 Source

A data-type for combining results of predicate evaluations.

Constructors

a ::: b infixr 5

Instances

(Eq a, Eq b) => Eq ((:::) a b)
(Show a, Show b) => Show ((:::) a b)

(#) :: a -> (a -> b) -> b Source

flip ($) - useful in combination with indexed access, e.g. (x ::: True ::: False)#_2 yields True.

hd :: (a ::: b) -> a Source

tl :: (a ::: b) -> b Source

_1 :: (a ::: b) -> a Source

_2 :: (a ::: (b ::: c)) -> b Source

_3 :: (a ::: (b ::: (c ::: d))) -> c Source

_4 :: (a ::: (b ::: (c ::: (d ::: e)))) -> d Source

_5 :: (a ::: (b ::: (c ::: (d ::: (e ::: f))))) -> e Source

_6 :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: g)))))) -> f Source

_7 :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: (g ::: h))))))) -> g Source

_8 :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: (g ::: (h ::: i)))))))) -> h Source

_9 :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: (g ::: (h ::: (i ::: j))))))))) -> i Source

_1' :: (a ::: b) -> a Source

_2' :: (a ::: b) -> b Source

_3' :: (a ::: (b ::: c)) -> c Source

_4' :: (a ::: (b ::: (c ::: d))) -> d Source

_5' :: (a ::: (b ::: (c ::: (d ::: e)))) -> e Source

_6' :: (a ::: (b ::: (c ::: (d ::: (e ::: f))))) -> f Source

_7' :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: g)))))) -> g Source

_8' :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: (g ::: h))))))) -> h Source

_9' :: (a ::: (b ::: (c ::: (d ::: (e ::: (f ::: (g ::: (h ::: i)))))))) -> i Source