georgii@gleontiev:~$ scala
Welcome to Scala version 2.8.1.final (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.
scala> val jbool = java.lang.Boolean.TRUE
jbool: java.lang.Boolean = true
scala> val sbool = true
sbool: Boolean = true
scala> def sboolMethod(sbool: Boolean) = print("got scala.Boolean " + sbool)
sboolMethod: (sbool: Boolean)Unit
scala> sboolMethod(sbool)
got scala.Boolean true
scala> sboolMethod(jbool)
<console>:9: error: type mismatch;
found : java.lang.Boolean
required: scala.Boolean
sboolMethod(jbool)
^
scala> implicit def jbool2sbool(bool: java.lang.Boolean): scala.Boolean = bool.booleanValue
jbool2sbool: (bool: java.lang.Boolean)Boolean
scala> sboolMethod(jbool) 开发者_JAVA百科
got scala.Boolean true
The question is: why isn't there a default implicit conversion from java.lang.Boolean
to scala.Boolean
? The question also stands for java.lang.Long
vs scala.Long
and probably other standard types (haven't tried all of them).
In 2.9, there is such a conversion, presumably to aid interoperability with Java. (Scala doesn't need it on its own, because it transparently boxes and unboxes primitives, which is perhaps why it wasn't included earlier.)
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