[jira] [Created] (GROOVY-7464) Iterable.intersect() is not commutative (and allows duplicates)

["Peter Ledbrook (JIRA)" <ji...@apache.org>]

Peter Ledbrook created GROOVY-7464:
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             Summary: Iterable.intersect() is not commutative (and allows duplicates)
                 Key: GROOVY-7464
                 URL: https://issues.apache.org/jira/browse/GROOVY-7464
             Project: Groovy
          Issue Type: Bug
          Components: groovy-jdk
            Reporter: Peter Ledbrook
            Assignee: Guillaume Laforge


The {{intersect()}} method on {{Iterable}} has different results depending on the order of the receiver object and the argument. For example,

{code}
def a = [1, 1, 2, 4]
def b = [1, 2, 2, 3]

println a.intersect(b)
println b.intersect(a)
{code}

prints out two different results ({{[1, 1, 2]}} and {{[1, 2, 2]}}).

Assuming that the operation should be commutative, i.e. the results should be the same for both, the question then becomes whether duplicates should even be returned at all.

I think the method should always return a set as intersection is a set operation. In other words, {{Iterable.intersect()}} becomes a convenience wrapper that converts the receiver object and the argument to sets.

This issue started as a discussion on the [dev mailing list|http://mail-archives.apache.org/mod_mbox/incubator-groovy-dev/201506.mbox/browser].



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