actualize
set-union
with
file-id
by morphism
:set → fidset;
:elem → fid;
∅ → ∅;
++ → ++;
# → #;
{ } → { };
∪ → ∪;
∩ → ∩;
\ → \;
-- → --;
∈ → ∈;
⊆ → ⊆;
s → fids;
s0 → fids0;
s1 → fids1;
s2 → fids2;
a → fid;
b → fid0;
c → fid1
end actualize