From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 10 Jun 2011 18:56:28 +0000 (-0400)
Subject: Add the kinda_equals comparison.
X-Git-Tag: 0.0.1~281
X-Git-Url: http://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=8c8a0f9d8df50b2fe29562790360dd615cf3e56a;p=spline3.git

Add the kinda_equals comparison.
---

diff --git a/src/Comparisons.hs b/src/Comparisons.hs
index b5d76d5..6d8dc70 100644
--- 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