let fingerprint pool r =
let env = { pool=pool ; vars=[] ; ctxt=F.p_true } in
let r' = {
cvars = Vmap.map (fp_map env) r.cvars ;
roots = Imap.map (fp_map env) r.roots ;
bases = List.map (fp_base env) r.bases ;
} in
env.vars , env.ctxt , r'