On Fri, Sep 14, 2018 at 5:56 PM ToddAndMargo <toddandma...@zoho.com> wrote:
> 'To opt into a non-nullable version of a type add the :D > "smiley" to it." > > This is confusing. And I don't think correct, but I could be wrong. > Curt stated it a lot better: > > If I say "my Int $x", > $x is now an Int, but an undefined Int. > > If I say "my Int $x = 42", > $x is an Int, but set to a defined value, 42. > > ":D" means that the variable is "defined". "non-nullable" is > a confusing way to state it. > Not exactly. "Defined" is a "now" thing; "non-nullable", via type smileys, is an "always" thing. It is defined now, and it can never be undefined. > To me ":D" means that the variable has something assigned to > and ":U" means that the variable has yet to have anything > assigned to it. > > If I were to rewrite this, I'd reverse D and U as that > is the way they evolve. All variables start out as :U. > This is the same misunderstanding: what is now, is not guaranteed to be so in the future. :U and :D provide such guarantees. Merely being defined or undefined right now says nothing about the future. -- brandon s allbery kf8nh allber...@gmail.com
