It will work for 0 if you use `number` instead of `js/Number`. Generally you shouldn't extend any js/* type
On Friday, June 6, 2014 9:57:38 AM UTC-7, Karsten Schmidt wrote: > > I'm trying to extend-protocol for numbers and various other types (incl. > collections & nil) in CLJS, so have been doing something like this (reduced > email version): > > (defprotocol PDeltaEq (delta= [a b])) > > (extend-protocol PDeltaEq > js/Number > (delta= [a b] :yay) > > nil > (delta= [_ b] (nil? b))) > > (delta= 1 1) > ;; :yay > > (delta= 0 0) > Error: No protocol method Foo.foo defined for type number: 0 > > Now I guessed, this might have something to do with JS' considering 0 as > `false` somewhere in the internal protocol machinery... and I was right! > Here's a relevant excerpt from the compiled protocol dispatch fn: > > var delta_EQ___2 = function(a, b) { > if (function() { > var and__3466__auto__ = a; > if (and__3466__auto__) { > return a.thi$ng$common$math$core$PDeltaEq$delta_EQ_$arity$2; > } else { > return and__3466__auto__; > } > }()) { > return a.thi$ng$common$math$core$PDeltaEq$delta_EQ_$arity$2(a, b); > } else { > .... > } > }; > > Obviously, with the `a` arg being 0, that `if (and__3466__auto__)` check > is always failing, so shouldn't this check be rewritten as: > > if (goog.isDefAndNotNull(and__3466__auto__) && > a.thi$ng$common$math$core$PDeltaEquals$delta_EQ_$arity$2) { > return a.thi$ng$common$math$core$PDeltaEquals$delta_EQ_$arity$2; > } > ... > > This change seems to fix this kind of error and AFAIK doesn't impact any > of my other (30+) test cases for this protocol... > > Thoughts? :) > > Thanks, K. > -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.