diff -r 1c999569643b -r acf2c31e22d4 samples/composition/src-api2.0-property/api/Arithmetica.java
--- a/samples/composition/src-api2.0-property/api/Arithmetica.java	Sat Jun 14 10:04:51 2008 +0200
+++ b/samples/composition/src-api2.0-property/api/Arithmetica.java	Sat Jun 14 10:04:53 2008 +0200
@@ -36,6 +36,10 @@
 
     private int sumRange1(int from, int to) {
         int len = to - from;
+        if (len < 0) {
+            len = -len;
+            from = to;
+        }
         int[] array = new int[len + 1];
         for (int i = 0; i <= len; i++) {
             array[i] = from + i;
@@ -44,7 +48,7 @@
     }
     
     private int sumRange2(int from, int to) {
-        return (from + to) * (to - from + 1) / 2;
+        return (from + to) * (Math.abs(to - from) + 1) / 2;
     }
 }
 // END: design.composition.arith2.0.property