Hello, there is an unwanted side effect: ( something like variable capture ) (%i1) foo(a):= bar(a)$ (%i2) bar(x):= a$ (%i3) foo(1); (%o3) 1 (%i4) bar(1); (%o4) a (%i5) a:2$ (%i6) foo(1); (%o6) 1 (%i7) bar(1); (%o7) 2 This should not be intended. A bug? Volker