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https://issues.apache.org/jira/browse/GROOVY-10964?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17697226#comment-17697226
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Paul King commented on GROOVY-10964:
------------------------------------
It all boils down to supporting "numeric equality" or "business equality" when
determining which numbers to remove. This is done using "NumberAwareComparator".
Consider this Java example:
{code:java}
jshell> var nums = Arrays.asList(1, 2, 2.0f, BigInteger.TWO)
nums ==> [1, 2, 2.0, 2]
jshell> nums.stream().filter(n -> !n.equals(2.0d)).toList()
$2 ==> [1, 2, 2.0, 2]
{code}
Attempting to "minus" the value "two" (I used a double, 2.0d) from the list
leaves it unchanged since it contains no doubles.
The idiomatic Groovy equivalent is:
{code:groovy}
assert [1, 2, 2.0f, 2.0G] - 2.0d == [1]
{code}
Here we are removing all "two" values.
If you don't need the fancy numeric equality, you can do the closer equivalent
of the above Java example:
{code}
assert nums.findAll(n -> !n.equals(2.0d)) == nums
{code}
Or the equivalent streams version.
> List.minus() slow for Numbers
> -----------------------------
>
> Key: GROOVY-10964
> URL: https://issues.apache.org/jira/browse/GROOVY-10964
> Project: Groovy
> Issue Type: Question
> Components: groovy-jdk
> Affects Versions: 2.4.0, 3.0.9, 4.0.9
> Reporter: Ingo Wilms
> Priority: Minor
> Labels: Collections, Groovy, List, Number
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> In List.minus() is a n*LOG\(n) version for comparable objects. Only for
> numbers, there is a dedicated slower n^2*LOG\(n) version. Is there a reason
> for this? It exists since 2.4.0 and hasn't changed much since then. Here is
> part of the code from version 4.0.9:
>
> {code:java}
> // if (nlgnSort && (head instanceof Comparable)) {
> //n*LOG(n) version
> Set<T> answer;
> if (head instanceof Number) {
> answer = new TreeSet<>(comparator);
> answer.addAll(self1);
> for (T t : self1) {
> if (t instanceof Number) {
> for (Object t2 : removeMe1) {
> if (t2 instanceof Number) {
> if (comparator.compare(t, (T) t2) == 0)
> answer.remove(t);
> }
> }
> } else {
> if (removeMe1.contains(t))
> answer.remove(t);
> }
> }
> } else {
> answer = new TreeSet<>(comparator);
> answer.addAll(self1);
> answer.removeAll(removeMe1);
> }
> for (T o : self1) {
> if (answer.contains(o))
> ansCollection.add(o);
> }
> } else {
> //n*n version {code}
> I fail to see why the whole extra block for numbers beginning with
> {code:java}
> if (head instanceof Number) { {code}
> is necessary.
>
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