Add the kinda_equals comparison.

diff --git a/src/Comparisons.hs b/src/Comparisons.hs
index b5d76d5b11d6da85ca386021be918041d83abd53..6d8dc70d846e08159c9c4ae6ea49b11a530a25a2 100644 (file)
--- a/src/Comparisons.hs
+++ b/src/Comparisons.hs
@@ -18,6 +18,20 @@ infix 4 ~=
 (~=) = almost_equals
 
 
+-- | Like 'almost_equals', except much more tolerant. The difference
+--   between the two arguments must be less than one percent of the sum
+--   of their magnitudes.
+kinda_equals :: Double -> Double -> Bool
+kinda_equals x y =
+    (abs (x - y)) < threshold
+    where
+      threshold = ((abs x) + (abs y)) / 100.0
+
+infix 4 ~~=
+(~~=) :: Double -> Double -> Bool
+(~~=) = kinda_equals
+
+
 -- | x is very positive if it is 'epsilon' greater than zero.
 very_positive :: Double -> Bool
 very_positive x =  x - epsilon > 0