The mistake of `null` is _not_ that it exists at all - it's often the case that you can't answer a question, and it's extremely useful to be able to model your

The mistake of `null` is _not_ that it exists at all - it's often the case that you can't answer a question, and it's extremely useful to be able to model your inability to answer a question! The mistake of `null` is instead that it forces every reference type to be an optional. This is a mistake because some things can in fact be known. In practice, when everything is optional, it's so boilerplate-heavy to enforce the condition "this is known" at runtime for every property that everyone inevitably ends up not enforcing that condition most of the time; the bugs arise when one side of a boundary assumes for expediency that the other side has enforced it. It is in general very reasonable for a function to return an optional bool; think of `List.tryHead [false, true, false]`. What is unreasonable is for all boolean functions to return optional bools.