include "arithmetics/nat.ma".
include "basics/lists/list.ma".
+include "basics/core_notation/singl_1.ma".
interpretation "iff" 'iff a b = (iff a b).
| #x; #y; #z; #w; #a; #b; #c; #d; #K; ncases (?:False); /2/ ]
##| #r1; #r2; #r1'; #r2'; #H1; #H2; #H3; #H4; #H5; #H6;
-*)
\ No newline at end of file
+*)