X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FComparisons.hs;h=6d8dc70d846e08159c9c4ae6ea49b11a530a25a2;hb=46b1f2e3741d6571c2f931371222f8970b6c7f63;hp=4bf4cebb69ece2947eb1deccf0dfa9cfda20f266;hpb=58cf11569acb270995d2de924dda03ef526647e2;p=spline3.git

diff --git a/src/Comparisons.hs b/src/Comparisons.hs
index 4bf4ceb..6d8dc70 100644
--- a/src/Comparisons.hs
+++ b/src/Comparisons.hs
@@ -3,8 +3,8 @@ module Comparisons
 where
 
 -- | epsilon is the value that will be used in all tests that require
---   some measure of "closeness." Increasing it will make those tests
---   more tolerant.
+--   some measure of \"closeness.\" Increasing it will make those
+--   tests more tolerant.
 epsilon :: Double
 epsilon = 0.0001
 
@@ -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