fb-util-0.1.0.1: Util/Predicate.hs

{-
  Copyright (c) Meta Platforms, Inc. and affiliates.
  All rights reserved.

  This source code is licensed under the BSD-style license found in the
  LICENSE file in the root directory of this source tree.
-}

module Util.Predicate
  ( Pred
  , predAnd
  , predTrue
  , predFalse
  ) where

import Control.Applicative (liftA2)

-- | Predicate function.
type Pred a = a -> Bool

-- | Combine two predicate functions to produce a new function that holds if
-- both input predicates hold.
predAnd :: Pred a -> Pred a -> Pred a
predAnd = liftA2 (&&)

-- | Predicate which returns True for all inputs
predTrue :: Pred a
predTrue _ = True

-- | Predicate which returns False for all inputs
predFalse :: Pred a
predFalse _ = False