enrich
set-union
with
functions
. to . : Nat × Nat → Set(Nat) prio 7 right;
variables
m : Nat;
n : Nat;
ns : Set(Nat);
axioms
range-def: n0 ∈ m to n ↔ m ≤ n0 ∧ n0 < n;
used for: s, ls;
end enrich