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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3557) Scala DataStream fold method should take fold function in secondary parameter list
Date Tue, 01 Mar 2016 12:57:19 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15173708#comment-15173708
] 

ASF GitHub Bot commented on FLINK-3557:
---------------------------------------

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1748#discussion_r54562674
  
    --- Diff: flink-streaming-scala/src/test/scala/org/apache/flink/streaming/api/scala/WindowFoldITCase.scala
---
    @@ -70,7 +70,7 @@ class WindowFoldITCase extends StreamingMultipleProgramsTestBase {
         source1
           .keyBy(0)
           .window(TumblingEventTimeWindows.of(Time.of(3, TimeUnit.MILLISECONDS)))
    -      .fold(("R:", 0), { (acc: (String, Int), v: (String, Int)) => (acc._1 + v._1,
acc._2 + v._2) })
    +      .fold(("R:", 0)){ (acc: (String, Int), v: (String, Int)) => (acc._1 + v._1,
acc._2 + v._2) }
    --- End diff --
    
    I have no strong preference here. I didn't introduce them initially because you also don't
insert a space between a function name and the first parameter list. But if you think that
it's better, I'll change it.


> Scala DataStream fold method should take fold function in secondary parameter list
> ----------------------------------------------------------------------------------
>
>                 Key: FLINK-3557
>                 URL: https://issues.apache.org/jira/browse/FLINK-3557
>             Project: Flink
>          Issue Type: Improvement
>          Components: DataStream API, Scala API
>    Affects Versions: 1.0.0
>            Reporter: Till Rohrmann
>            Assignee: Till Rohrmann
>            Priority: Minor
>
> The current Scala DataStream API offers a {{fold}} method. The {{fold}} method takes
two parameters, the initial value and the fold function. However, both parameters are specified
in the same parameter list. This makes it clumsy to provide a multi-line anonymous function
as the fold function parameter in Scala. One would have to wrap the function in an additional
pair of curly braces. This could be avoided by having a second parameter list which takes
the fold function. This would, additionally, be consistent with Scala's collection API.
> Old style
> {code}
> windowedStream.fold(("R:", 0), { (acc: (String, Int), v: (String, Int)) => (acc._1
+ v._1, acc._2 + v._2) })
> {code}
> vs. new style
> {code}
> windowedStream.fold(("R:", 0)){ (acc, v) => (acc._1 + v._1, acc._2 + v._2) }
> {code}
> These changes are API breaking.



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