.decl A(x:symbol)
A("abc123").
A("bc123a").
A("c123ab").
A("123abc").
A("23abc1").
A("3abc12").

.decl B(x:symbol)
B(substr(x,2,2)) :- A(x).

.output B()

.decl Nullary()
Nullary().

.decl C(x:symbol)
C(substr("12",22,12)) :- Nullary().

.output C()
