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https://issues.apache.org/jira/browse/JENA-880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14316189#comment-14316189
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Andy Seaborne commented on JENA-880:
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Having markers could mean that expressions could be classified as "well
behaved" expressions (no calls of the first kind) which should make them "sort
stable".
Forms of the second kind are well behaved for sorting because they are stable
for a given input row.
> Create marker interfaces for expressions to indicate when they are not pure
> functions.
> --------------------------------------------------------------------------------------
>
> Key: JENA-880
> URL: https://issues.apache.org/jira/browse/JENA-880
> Project: Apache Jena
> Issue Type: Task
> Reporter: Andy Seaborne
> Priority: Minor
>
> Some expression forms look like function but they aren't in their evaluation.
> These come in two kinds: forms that are not determined by their arguments
> (including zero arguments) and those where argumnets are not evaluated before
> the function is called.
> Of the first kind:\\
> {{uuid}}, {{uuidstr}}, {{rand}}, {{bnode}} (both zero and one argument forms)
> Of the second kind:\\
> {{coalesce}}, {{if}}, {{&&}} {{||}} {{bound}}, {{IN}}, {{NOT IN}}
> Marker interfaces may aid optimization algorithms.
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