[jira] [Created] (FLINK-3557) Scala DataStream fold method should take fold function in secondary parameter list

["Till Rohrmann (JIRA)" <ji...@apache.org>]

Till Rohrmann created FLINK-3557:
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             Summary: 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: (String, Int), v: (String, Int)) => (acc._1 + v._1, acc._2 + v._2) }
{code}

These changes are API breaking.



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