p6 = p2; p6 = p2 - s;
CPPUNIT_ASSERT( p3 == p5 );
CPPUNIT_ASSERT( p4 == p6 );
+ p5 = p2; p5 = s + p2;
+ p6 = p2; p6 = s - p2;
+ CPPUNIT_ASSERT( p3 == p5 );
+ CPPUNIT_ASSERT( p4 == -p6 );
p5 = p2; p5 += s;
p6 = p2; p6 -= s;
CPPUNIT_ASSERT( p3 == p5 );