Or is this just the place where I do need to catch errors and process them? And if that is so, isn't it at odds with the whole concept of writing intentional code?
No it's not. The author touches on this:
Note the word intentional. In some cases, we do expect calls to fail. So we just handle it like everyone else would, but since we can emulate sum-types in Erlang, we can do better than languages with no concept of a sum-type.
So handle errors you expect explicitly and let the rest crash.
case user:authenticate(Username, Password) of
{ok, UserRecord} -> ...;
{error, notfound} -> ...;
{error, badpass} -> ...
end,
No it's not. The author touches on this:
Note the word intentional. In some cases, we do expect calls to fail. So we just handle it like everyone else would, but since we can emulate sum-types in Erlang, we can do better than languages with no concept of a sum-type.
So handle errors you expect explicitly and let the rest crash.