{-# OPTIONS -fno-implicit-prelude #-}
module Test.Utility where

-- import Test.QuickCheck (Arbitrary(..))

import qualified Algebra.Real                  as Real
import qualified Algebra.Ring                  as Ring

import PreludeBase
import NumericPrelude


equalList :: Eq a => [a] -> Bool
equalList xs =
   -- 'drop 1' instead of 'take' for suppression of error
   and (zipWith (==) xs (drop 1 xs))


approxEqual :: (Real.C a) => a -> a -> a -> Bool
approxEqual eps x y =
   2 * abs (x-y) <= eps * (abs x + abs y)

approxEqualListRel :: (Real.C a) => a -> [a] -> Bool
approxEqualListRel eps xs =
   let n = fromIntegral $ length xs
   in  approxEqualListAbs (eps * n * sum (map abs xs)) xs

approxEqualListAbs :: (Real.C a) => a -> [a] -> Bool
approxEqualListAbs eps xs =
   let n = fromIntegral $ length xs
       s = sum xs
   in  sum (map (\x -> abs (n*x-s)) xs)  <=  eps