[ "nat_le ( ?≤? )" "nat_le_pred" "nat_le_plus" "nat_le_minus" "nat_le_minus_plus" "nat_le_max" * ]
[ "nat_max ( ?∨? )" * ]
[ "nat_minus ( ?-? )" "nat_minus_plus" * ]
- [ "nat_plus ( ?+? )" * ]
+ [ "nat_plus ( ?+? )" "nat_plus_pred" * ]
[ "nat_pred ( ↓? )" "nat_pred_succ" * ]
[ "nat_succ ( ↑? )" "nat_succ_iter" "nat_succ_tri" * ]
[ "nat ( 𝟎 )" "nat_iter ( ?^{?}? )" *"nat_tri" ]