Created
June 18, 2010 02:00
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Scala equality pitfall
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| scala> null == 42 | |
| res0: Boolean = false | |
| scala> (null:java.lang.Integer) == 42 | |
| java.lang.NullPointerException | |
| at scala.runtime.BoxesRunTime.equalsNumNum(Unknown Source) | |
| at scala.runtime.BoxesRunTime.equalsNumObject(Unknown Source) | |
| at .<init>(<console>:6) | |
| at .<clinit>(<console>) | |
| at RequestResult$.<init>(<console>:9) | |
| at RequestResult$.<clinit>(<console>) | |
| at RequestResult$scala_repl_result(<console>) | |
| at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) | |
| at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) | |
| at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) | |
| at java.lang.reflect.Method.invoke(Method.java:616) | |
| at scala.tools.nsc.Interpreter$Request$$anonfun$loadAndRun$1$$anonfun$apply$18.apply(Interpreter.scala:981) | |
| at scala.tools.nsc.Interpreter$Request$$anonfun$loadAndRun$1$$anonfun... |
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I posted the equality problem to the Scala mailing list, and within a couple hours, a fix was committed. Hooray for Paul Phillips and the rest of the Scala dev team.
http://scala-programming-language.1934581.n4.nabble.com/and-equals-td2261488.html#a2262102
http://lampsvn.epfl.ch/trac/scala/changeset/22379/