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) (.getClass 1) :- (U java.lang.Class nil) (class 1) :- java.lang.Class So the equivalent type of java.lang.Object (in Java-land) is (U java.lang.Object nil) (in Clojure-land). The exception to the implicit nil rule would be when a the result of an interop expression is a primitive value. A Java primitive cannot be null. (. Integer MAXVALUE) :- int Hopefully I expressed my thoughts clearly. Does this strategy seem correct? Are there any other uses of null that I should be handling? Thanks, Ambrose -- 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
