free c:channel.

fun h(bitstring):bitstring.

const a,b:bitstring.

event A(bitstring).

const ok,ko:bitstring.

axiom x:bitstring,y:bitstring;
  event(A(choice[x,y])) ==> x=a;
  event(A(choice[x,y])) ==> y=a.

process
  in(c,x:bitstring);
    event A(x);
    out(c,diff[a,x])

(* EXPECTPV
RESULT Observational equivalence is true.
0.024s (user 0.020s + system 0.004s), max rss 8704K
END *)
