It's the other way around: false is boxed into Boolean/FALSE. Here's the if
stmt:
public Object eval() {
Object t = testExpr.eval();
if(t != null && t != Boolean.FALSE)
return thenExpr.eval();
return elseExpr.eval();
}
On Friday, April 13, 2012 12:45:02 PM UTC-7, Andy Fingerhut wrote:
>
> One little nit that confuses me.
>
> 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?
>
> Thanks,
> Andy
>
>
> On Fri, Apr 13, 2012 at 11:41 AM, Sean Corfield <seancorfi...@gmail.com>wrote:
>
>> On Fri, Apr 13, 2012 at 3:33 AM, Vinzent <ru.vinz...@gmail.com> wrote:
>> > Just like Boolean's javadoc puts a strong
>> > emphasis on the fact that public Boolean(boolean value) constructor
>> usually
>> > shouldn't be used, clojure's docstring should say that (= x false) may
>> give
>> > you a result which will confuse you, so you'd better use 'false?'
>> instead.
>>
>> (def f (Boolean. false))
>> (false? f)
>> ;; => false
>> (true? f)
>> ;; => false
>> (= f false)
>> ;; => true
>> (if f :t :f)
>> ;; => :t
>>
>> So 'false?' doesn't help you here.
>>
>> No one should be using (Boolean. false) in Clojure code - we have true
>> / false. Why create a Java object whose documentation says not to do
>> it?
>>
>> So if anyone runs into this problem _in real world code_ it's because
>> they are calling a Java API that somehow returns a Java Boolean object
>> embedded in the result. If you are working with a Java data structure
>> full of _Objects_ then you need to take care of converting those
>> Object instances into appropriate Clojure values. Calling (boolean v)
>> is sufficient to convert the Java Object to a Clojure true/false
>> value.
>> --
>> Sean A Corfield -- (904) 302-SEAN
>> An Architect's View -- http://corfield.org/
>> World Singles, LLC. -- http://worldsingles.com/
>>
>> "Perfection is the enemy of the good."
>> -- Gustave Flaubert, French realist novelist (1821-1880)
>>
>> --
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>
>
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