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-----------------------------------------------------------------------------
-- |
-- Module : AFRPMiscellany
-- Copyright : (c) Yale University, 2003
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : antony@apocalypse.org
-- Stability : provisional
-- Portability : non-portable (uses GHC extensions)
--
-- Collection of entities that really should be part
-- the Haskell 98 prelude or simply have no better
-- home.
--
module AFRPMiscellany (
-- Reverse function composition
( # ), -- :: (a -> b) -> (b -> c) -> (a -> c), infixl 9
-- Arrow plumbing aids
dup, -- :: a -> (a,a)
swap, -- :: (a,b) -> (b,a)
-- Maps over lists of pairs
mapFst, -- :: (a -> b) -> [(a,c)] -> [(b,c)]
mapSnd, -- :: (a -> b) -> [(c,a)] -> [(c,b)]
-- Generalized tuple selectors
sel3_1, sel3_2, sel3_3,
sel4_1, sel4_2, sel4_3, sel4_4,
sel5_1, sel5_2, sel5_3, sel5_4, sel5_5,
-- Floating point utilities
fDiv, -- :: (RealFrac a, Integral b) => a -> a -> b
fMod, -- :: RealFrac a => a -> a -> a
fDivMod -- :: (RealFrac a, Integral b) => a -> a -> (b, a)
) where
infixl 9 #
infixl 7 `fDiv`, `fMod`
------------------------------------------------------------------------------
-- Reverse function composition
------------------------------------------------------------------------------
( # ) :: (a -> b) -> (b -> c) -> (a -> c)
f # g = g . f
------------------------------------------------------------------------------
-- Arrow plumbing aids
------------------------------------------------------------------------------
dup :: a -> (a,a)
dup x = (x,x)
swap :: (a,b) -> (b,a)
swap ~(x,y) = (y,x)
------------------------------------------------------------------------------
-- Maps over lists of pairs
------------------------------------------------------------------------------
mapFst :: (a -> b) -> [(a,c)] -> [(b,c)]
mapFst f [] = []
mapFst f ((x, y) : xys) = (f x, y) : mapFst f xys
mapSnd :: (a -> b) -> [(c,a)] -> [(c,b)]
mapSnd f [] = []
mapSnd f ((x, y) : xys) = (x, f y) : mapSnd f xys
------------------------------------------------------------------------------
-- Generalized tuple selectors
------------------------------------------------------------------------------
-- Triples
sel3_1 (x,_,_) = x
sel3_2 (_,x,_) = x
sel3_3 (_,_,x) = x
-- 4-tuples
sel4_1 (x,_,_,_) = x
sel4_2 (_,x,_,_) = x
sel4_3 (_,_,x,_) = x
sel4_4 (_,_,_,x) = x
-- 5-tuples
sel5_1 (x,_,_,_,_) = x
sel5_2 (_,x,_,_,_) = x
sel5_3 (_,_,x,_,_) = x
sel5_4 (_,_,_,x,_) = x
sel5_5 (_,_,_,_,x) = x
------------------------------------------------------------------------------
-- Floating point utilities
------------------------------------------------------------------------------
-- Floating-point div and modulo operators.
fDiv :: (RealFrac a, Integral b) => a -> a -> b
fDiv x y = fst (fDivMod x y)
fMod :: RealFrac a => a -> a -> a
fMod x y = snd (fDivMod x y)
fDivMod :: (RealFrac a, Integral b) => a -> a -> (b, a)
fDivMod x y = (q, r)
where
q = (floor (x/y))
r = x - fromIntegral q * y