The good news is that you could use both libraries. `sqlite3cpp::database` supports "attaching" mode that won't close a `sqlite3` instance after sqlite3cpp::database going out of scope. Here is an example for coexisting with SqliteModernCpp:
// db inited by SqliteModernCpp
sqlite::database db(":memory:");
{
sqlite3cpp::database attached_db(db.connection().get());
// create the SQL function as you like
attached_db.create_scalar("mutiply", [](int x, int y) {
return x * y;
});
} // attached_db is going out of scope
// SQL scalar function `multiply` is still availble
db << "CREATE TABLE numbers (n1 INTEGER, n2 INTEGER);";
db << "SELECT multiply(n1, n2) from numbers;";
Note that SqliteModernCpp provides customization of SQL function as well as sqlite3cpp. Though it doesn't seem to have aggregate function supporting
(i.e. sqlite3cpp::database::create_aggregate).
If C++ is your thing,
https://github.com/yangacer/sqlite3cpp
might be interesting. It intelligently wraps C++ functions as SQL functions.
Author here and looks forward feedbacks :).
Note that SqliteModernCpp provides customization of SQL function as well as sqlite3cpp. Though it doesn't seem to have aggregate function supporting (i.e. sqlite3cpp::database::create_aggregate).