On Thu, Apr 19, 2012 at 2:46 PM, Ambrose Bonnaire-Sergeant <abonnaireserge...@gmail.com> wrote: > Hi, > > I've been doing some thinking about the treatment of nil in a > statically typed version of Clojure. > > It occurs to me that nil is significantly different to Java's null > reference, which > is almost a Bottom type. > > Java's null is a subtype of any reference type. > Clojure's nil is just nil, subtype to nothing except itself. > > To accomodate this, nil should be implicitly added to the result > type of any interaction with Java via interop. > > (Union syntax: (U x0 .. xn) is the union of types x0..nx) > > <expr> :- <type of expr> > > (Integer. 1) :- (U java.lang.Integer nil)
Constructor calls can never evaluate to null. > (.getClass 1) :- (U java.lang.Class nil) I'm pretty sure the Object#getClass method can never return null either. On the other hand, (.get a-java-util-map foo) :- (U java.lang.Object nil) :) -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
