--- a/Fraction.st	Wed Apr 29 22:19:08 2009 +0200
+++ b/Fraction.st	Fri May 01 19:19:55 2009 +0200
@@ -145,10 +145,11 @@
 !Fraction class methodsFor:'constants'!
 
 pi
-    "return the constant pi as Fraction"
+    "return an approximation of the constant pi as Fraction.
+     The approx. returned here has an error smaller than representable by float instances"
 
     ^ self 
-        numerator:  314159265358979323846264343
+        numerator:314159265358979323846264343
         denominator:100000000000000000000000000
 
 "/    ^ self 
@@ -164,6 +165,23 @@
     "Modified: 5.11.1996 / 11:11:44 / cg"
 !
 
+pi_approximation
+    "return an approximation of the constant pi as Fraction.
+     The approx. returned is good for 6 valid digits and has an error of less than -2.67-07.
+     The value might be useful to avoid floating point numbers in graphic rendering code,
+     where 6 digits of precision are usually good enough."
+
+    ^ self 
+        numerator:355
+        denominator:113
+
+    "
+     Fraction pi         
+     Fraction pi asFloat
+     Float pi - Fraction pi_approximation asFloat            
+    "
+!
+
 unity
     "return the neutral element for multiplication (1 / 1)"
 
@@ -1105,7 +1123,7 @@
 !Fraction class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/Fraction.st,v 1.75 2008-10-21 10:13:29 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/Fraction.st,v 1.76 2009-05-01 17:19:55 cg Exp $'
 ! !
 
 Fraction initialize!