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|
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.Bool
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : portable
--
-- The 'Bool' type and related functions.
--
-----------------------------------------------------------------------------
module Data.Bool (
-- * Booleans
Bool(..),
-- ** Operations
(&&),
(||),
not,
otherwise,
bool,
) where
import GHC.Base
-- $setup
-- >>> import Prelude
-- | Case analysis for the 'Bool' type. @'bool' x y p@ evaluates to @x@
-- when @p@ is 'False', and evaluates to @y@ when @p@ is 'True'.
--
-- This is equivalent to @if p then y else x@; that is, one can
-- think of it as an if-then-else construct with its arguments
-- reordered.
--
-- @since 4.7.0.0
--
-- ==== __Examples__
--
-- Basic usage:
--
-- >>> bool "foo" "bar" True
-- "bar"
-- >>> bool "foo" "bar" False
-- "foo"
--
-- Confirm that @'bool' x y p@ and @if p then y else x@ are
-- equivalent:
--
-- >>> let p = True; x = "bar"; y = "foo"
-- >>> bool x y p == if p then y else x
-- True
-- >>> let p = False
-- >>> bool x y p == if p then y else x
-- True
--
bool :: a -> a -> Bool -> a
bool f _ False = f
bool _ t True = t
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