A = <b> B <c> C.
B = DD ( AA ( BB ( CC)), F(C, CC), G).
C = BL.
D = F(G).
G =.
F(X) = <x> X(X).
X =. 
List(S) ~ S {S}.
Alt(X1, Y1) : Alt1(X1, Y1) | Alt2(X1, Y1).
List2(X2, Y2) ~ Alt2(X2,Y2) {Alt1(X2,Y2)}.
Alt1(X1, Y1) = X1(Y1).
Alt2(X1, Y1) =.
AA(S, SS) =.
BB(S) =.
CC(S) =.
DD(N,O,P) =.
A =.
F =.