src/Comparisons.hs

   1 module Comparisons
   2 where
   3
   4 -- | epsilon is the value that will be used in all tests that require
   5 --   some measure of "closeness." Increasing it will make those tests
   6 --   more tolerant.
   7 epsilon :: Double
   8 epsilon = 0.0001
   9
  10
  11 -- | x almost equals y if x is within 'epsilon' of y.
  12 almost_equals :: Double -> Double -> Bool
  13 almost_equals x y = (abs (x - y)) < epsilon
  14
  15 infix 4 ~=
  16 (~=) :: Double -> Double -> Bool
  17 (~=) = almost_equals
  18
  19
  20 -- | x is very positive if it is 'epsilon' greater than zero.
  21 very_positive :: Double -> Bool
  22 very_positive x =  x - epsilon > 0
  23
  24
  25 -- | Takes a list of Doubles and returns the ones which are not very
  26 --   positive.
  27 non_very_positive_entries :: [Double] -> [Double]
  28 non_very_positive_entries = filter (not . very_positive)