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Comment by jefffoster | Hacker News Reader

In Java, the compiler won't tell you that a variable may be null. In Haskell (at least when you compile with -Wall, strange this particular warning isn't the default) you'll get an error if you've failed to handle all the variations of data that you've provided.

There's a good presentation my Yaron Minsky about OCaml in the real world where he cites this as a major advantage (in OCaml, failing to match all patterns is an error by default).

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> In Java, the compiler won't tell you that a variable may be null. In Haskell (at least when you compile with -Wall, strange this particular warning isn't the default) you'll get an error if you've failed to handle all the variations of data that you've provided.

    Connection con = DriverManager.getConnection(
                         "jdbc:myDriver:myDatabase",
                         username,
                         password);

    Statement stmt = con.createStatement();
    ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM Table1");

    while (rs.next()) {
        int x = rs.getInt("a");
        String s = rs.getString("b");
        float f = rs.getFloat("c");
    }

It's not that bad. In the above example, you either get an SQLException or a ResultSet. ResultSet is your option type here. It wont' be null - it might or might not contain values.

There might be a lot of good things about Haskell(I am not that familiar to make a call), but seriously, Maybe doesn't look that great.

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