2009/5/4 Rich Hickey <richhic...@gmail.com>: > > > > On May 4, 7:14 am, Laurent PETIT <laurent.pe...@gmail.com> wrote: >> Hi, >> >> 2009/5/4 Rich Hickey <richhic...@gmail.com> >> >> >> >> >> >> > On May 4, 1:53 am, Laurent PETIT <laurent.pe...@gmail.com> wrote: >> > > 2009/5/4 Christophe Grand <christo...@cgrand.net> >> >> > > > Janico Greifenberg a écrit : >> > > > > Hi, >> >> > > > > I encountered unexpected behavior of the 'if' form in clojure when >> > > > > using >> > > > > instances of java.lang.Boolean as the condition. I wanted to convert >> > > > > input strings to booleans and used the constructor of the Boolean >> > > > > class >> > > > > with the string parameter. However, when I pass these values as a >> > > > > condition to if, the true-branch always gets executed. For example: >> >> > > > > > (if (Boolean. "true") 1 2) >> > > > > 1 >> > > > > > (if (Boolean. "false") 1 2) >> > > > > 1 >> >> > > > > It seems to me that this has to do with the identity of the objects, >> > > > > as >> > > > > (Boolean. "false") is not identical (although equal) to the clojure >> > > > > literal false. Is this behavior intentional or a bug? >> >> > > > > The problem does not occur when I use Boolean/parseBoolean which >> > > > > returns >> > > > > a lower case boolean. >> >> > > > It's intentional, Rich said "for efficiency only canonic false is >> > > > logical false in >> > > > Clojure." inhttp://groups.google.com/group/clojure/msg/81ba3175da9a877c >> >> > > > Workaround: >> > > > > (if (boolean (Boolean. "false")) 1 2) >> > > > 2 >> >> > > At the cost of a lesser experience concerning java interoperability, >> > > then ? >> >> > > Isn't that "premature optimization" ? ;-) >> >> > Not at all. The cost would apply to all usage of 'if' (i.e. all >> > conditionals). >> >> I don't know whether the impact would be that big, it was just a question. >> >> But whatever, shouldn't this be clearly stated in the documentation of >> the 'if' special form (http://clojure.org/special_forms#toc2) ? >> > > Yes, I've enhanced the documentation here: > > http://clojure.org/special_forms#if > > Is that better?
Not just better: almost perfect ! :-) --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
