Set: pp::colors
  Set: pp::unicode
proj1 (pair 10 20) : ℕ
10
20
pair 20 30
10
20
40
  Defined: NZ
  Assumed: t
proj1 t : ℕ
proj2 t : 1 ≤ proj1 t
  Assumed: t2
proj2 t2 : ℕ ⨯ ℕ