every s1 := insert(set([]),!&lcase) ----> none
s2 := set(["a","aa","ab","b",1,2,3,4]) ----> set(8)
s3 := s1 ++ s2 ----> set(32)
s4 := s1 ** s2 ----> set(2)
s5 := s1 -- s2 ----> set(24)
*s3 ----> 32
*s4 ----> 2
*s5 ----> 24
Run-time error 119 at line 17 in expr05.icn
set expected
offending value: 'a'