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From "Marko A. Rodriguez (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TINKERPOP3-780) Use of fold() in repeat()
Date Sat, 01 Aug 2015 17:38:04 GMT

    [ https://issues.apache.org/jira/browse/TINKERPOP3-780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14650471#comment-14650471
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Marko A. Rodriguez commented on TINKERPOP3-780:
-----------------------------------------------

{{RepeatStep}} leverages global children (not local children). As such, {{RepeatStep}} does
not {{reset()}} with each incoming object. This ensures that {{repeat()}} can work in OLAP
beyond the "star graph."

The trick would be to figure out how to "auto reset" {{ReducingBarrierStep}}. Perhaps if it
doesn't have an incoming object, then {{FastNoSuchElementException}}. However, that means:
{{g.V.filter{true}.groupCount()}} would return nothing as opposed to {{[:]]}} (likewise for
{{sum()}}, {{mean()}}, etc.



> Use of fold() in repeat()
> -------------------------
>
>                 Key: TINKERPOP3-780
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP3-780
>             Project: TinkerPop 3
>          Issue Type: Bug
>          Components: process
>    Affects Versions: 3.0.0-incubating
>            Reporter: stephen mallette
>            Assignee: Marko A. Rodriguez
>             Fix For: 3.0.1-incubating, 3.1.0-incubating
>
>
> I would expect these two traversals to be equivalent:
> {code}
> gremlin> g = TinkerFactory.createModern().traversal()
> ==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
> gremlin> g.V(1).repeat(out().fold().unfold()).times(2)
> gremlin> g.V(1).repeat(out()).times(2)
> ==>v[5]
> ==>v[3]
> {code}
> Also note something [~dkuppitz] pointed out:
> {code}
> gremlin> g.V(1).repeat(out().fold()).times(1)
> ==>[]
> gremlin> g.V(1).out().fold()
> ==>[v[3], v[2], v[4]]
> {code}



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