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https://issues.apache.org/jira/browse/GROOVY-9605?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Paul King resolved GROOVY-9605.
-------------------------------
Fix Version/s: 2.5.13
3.0.5
4.0.0-alpha-1
Resolution: Fixed
Proposed PR merged. Thanks for spotting the issue!
> leftShift operator does not work on BigInteger (throws
> UnsupportedOperationException)
> -------------------------------------------------------------------------------------
>
> Key: GROOVY-9605
> URL: https://issues.apache.org/jira/browse/GROOVY-9605
> Project: Groovy
> Issue Type: Bug
> Components: groovy-jdk
> Affects Versions: 3.0.4
> Environment: Groovy 3.0.4 Windows and Linux
> Reporter: Bertrand Martin
> Assignee: Paul King
> Priority: Major
> Fix For: 4.0.0-alpha-1, 3.0.5, 2.5.13
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> h1. Problem
> The _leftShift_ operator ({{<<}}) does not work on *BigInteger* (see
> [StackOverflow
> question|https://stackoverflow.com/questions/62496971/leftshift-method-on-biginteger-in-groovy]).
> The *leftShift()* method is however described in [Groovy's JDK
> enhancements|http://docs.groovy-lang.org/latest/html/api/org/codehaus/groovy/runtime/DefaultGroovyMethods.html#leftShift(java.lang.Number,java.lang.Number)].
> The below code fails with Groovy 3.0.4:
> {code:groovy}
> Integer i = new Integer(3)
> assert 12 == i << 2
> Number b = new BigInteger("3")
> assert 12 == b << 2
> {code}
> It throws an exception:
> {noformat}
> Caught: java.lang.UnsupportedOperationException: Cannot use leftShift() on
> this number type: java.math.BigInteger with value: 3
> java.lang.UnsupportedOperationException: Cannot use leftShift() on this
> number type: java.math.BigInteger with value: 3
> at test.run(test.groovy:5)
> {noformat}
> Consequence: you cannot use the {{<<}} operator on a _Number_ if this number
> is a _BigInteger_.
> h1. Understanding of the problem
> (I'm not familiar with the code)
> The
> [BigIntegerMath|https://github.com/groovy/groovy-core/blob/master/src/main/org/codehaus/groovy/runtime/typehandling/BigIntegerMath.java]
> class does not implement the _leftShift()_ method.
> Also, please note that JDK's
> [BigInteger|https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#shiftLeft-int-]
> method for this operation is *not* _leftShift()_ but _shiftLeft()_!
> h1. Workaround
> Using mixins, the below code works:
> {code:groovy}
> class EnhancedNumber {
> static def originalLeftShift =
> org.codehaus.groovy.runtime.DefaultGroovyMethods.&leftShift
> static Number leftShift(Number self, Number operand) {
> self.class == BigInteger ? self.shiftLeft(operand) :
> originalLeftShift(self, operand)
> }
> }
> Number.mixin(EnhancedNumber)
> Integer i = new Integer(3)
> assert 12 == i << 2
> Number b = new BigInteger("3")
> assert 12 == b << 2
> {code}
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