Andy Fingerhut <andy.finger...@gmail.com> writes: > Boolean/FALSE is documented as being of type Boolean in Java > documentation, yet it is treated by Clojure the same as primitive > boolean false: > > user=> (clojure-version) > "1.3.0" > user=> (if Boolean/FALSE "logical true" "logical false") > "logical false" > user=> (identical? Boolean/FALSE false) > true > > Does anyone know why?
That's the canonical false Boolean object you get when auto-boxing the primitive boolean false, or when calling (Boolean/valueOf). ,----[ JLS: 5.1.7. Boxing Conversion ] | At run time, boxing conversion proceeds as follows: | | - If p is a value of type boolean, then boxing conversion converts p | into a reference r of class and type Boolean, such that | r.booleanValue() == p | | [...] | | If the value p being boxed is true, false, a byte, or a char in the | range \u0000 to \u007f, or an int or short number between -128 and 127 | (inclusive), then let r1 and r2 be the results of any two boxing | conversions of p. It is always the case that r1 == r2. `---- Thus, checking "t != Boolean.FALSE" as clojure's `if` implementation does is perfectly fine, because unless you've created a new Boolean object yourself, the spec guarantees that you may check on identity. (I totally agree with Rich that having a way to create new Boolean instances is completely flawed.) Bye, Tassilo -- 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
