From: Jean Privat <jean@pryen.org>
Date: Thu, 20 Nov 2014 14:02:44 +0000 (-0500)
Subject: lib: add Float::is_approx to compare floats
X-Git-Tag: v0.6.11~23^2~1
X-Git-Url: http://nitlanguage.org

lib: add Float::is_approx to compare floats

Signed-off-by: Jean Privat <jean@pryen.org>
---

diff --git a/lib/standard/kernel.nit b/lib/standard/kernel.nit
index 2e9c9ae..2f2df4b 100644
--- a/lib/standard/kernel.nit
+++ b/lib/standard/kernel.nit
@@ -331,6 +331,21 @@ universal Float
 		end
 	end
 
+	# Compare float numbers with a given precision.
+	#
+	# Because of the loss of precision in floating numbers,
+	# the `==` method is often not the best way to compare them.
+	#
+	# ~~~
+	# assert 0.01.is_approx(0.02, 0.1)   == true
+	# assert 0.01.is_approx(0.02, 0.001) == false
+	# ~~~
+	fun is_approx(other, precision: Float): Bool
+	do
+		assert precision >= 0.0
+		return self <= other + precision and self >= other - precision
+	end
+
 	redef fun max(other)
 	do
 		if self < other then