Data.Predicate

Documentation

data Boolean f t

A Bool-like type where each branch True or False carries some meta-data which is threaded through Predicate evaluation.

Constructors

F (Maybe f)

logical False with some meta-data

T t

logical True with some meta-data

Instances

Monad (Boolean f)

Functor (Boolean f)

MonadPlus (Boolean f)

Applicative (Boolean f)

Alternative (Boolean f)

(Eq f, Eq t) => Eq (Boolean f t)

(Show f, Show t) => Show (Boolean f t)

class Predicate p a where

The Predicate class declares the function apply which evaluates the predicate against some value, returning a value of type Boolean. Besides being parameterised over predicate type and predicate parameter, the class is also parameterised over the actual types of T's and F's meta-data.

Associated Types

type FVal p

type TVal p

Methods

apply :: p -> a -> Boolean (FVal p) (TVal p)

Instances

Predicate Param Request

Predicate AcceptThrift Request

Predicate AcceptJson Request

Predicate Accept Request

(Predicate a c, Predicate b c, ~ * (FVal a) (FVal b)) => Predicate (:&: a b) c

(Predicate a c, Predicate b c, ~ * (FVal a) (FVal b)) => Predicate (:||: a b) c

(Predicate a c, Predicate b c, ~ * (TVal a) (TVal b), ~ * (FVal a) (FVal b)) => Predicate (:|: a b) c

Predicate (Fail f t) a

Predicate (Const f t) a

data Const f t where

A Predicate instance which always returns T with the given value as T's meta-data.

Constructors

Const :: t -> Const f t

Instances

Show t => Show (Const f t)

Predicate (Const f t) a

data Fail f t where

A Predicate instance which always returns F with the given value as F's meta-data.

Constructors

Fail :: f -> Fail f t

Instances

Show f => Show (Fail f t)

Predicate (Fail f t) a

data a :|: b

A Predicate instance corresponding to the logical OR connective of two Predicates. It requires the meta-data of each True branch to be of the same type.

Constructors

a :|: b

Instances

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

(Predicate a c, Predicate b c, ~ * (TVal a) (TVal b), ~ * (FVal a) (FVal b)) => Predicate (:|: a b) c

type :+: a b = Either a b

data a :||: b

A Predicate instance corresponding to the logical OR connective of two Predicates. The meta-data of each True branch can be of different types.

Constructors

a :||: b

Instances

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

(Predicate a c, Predicate b c, ~ * (FVal a) (FVal b)) => Predicate (:||: a b) c

data a :*: b

Data-type used for tupling-up the results of :&:.

Constructors

a :*: b

Instances

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

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

data a :&: b

A Predicate instance corresponding to the logical AND connective of two Predicates.

Constructors

a :&: b

Instances

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

(Predicate a c, Predicate b c, ~ * (FVal a) (FVal b)) => Predicate (:&: a b) c