English
If h is DiophFn, then the two-argument DiophFn composed with f and g is Diophantine.
Русский
Если h диагофантова функция, композиция с f и g диагофантová.
LaTeX
$$$$\mathrm{DiophFn}(f) \Rightarrow \mathrm{DiophFn}(g) \Rightarrow \mathrm{DiophFn}(\lambda v, h(f(v), g(v)))$$$$
Lean4
theorem diophFn_comp2 {h : ℕ → ℕ → ℕ} (d : DiophFn fun v : Vector3 ℕ 2 => h (v &0) (v &1)) :
DiophFn fun v => h (f v) (g v) :=
diophFn_comp d [f, g] ⟨df, dg⟩