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https://issues.apache.org/jira/browse/FLINK-1255?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aljoscha Krettek resolved FLINK-1255.
-------------------------------------
Resolution: Fixed
Fix Version/s: 0.9
Assignee: Aljoscha Krettek
Fixed by adding a FAQ entry explaining the situation in:
https://github.com/apache/flink/commit/2bdfd88eb1fabd0e93bd6293213e7157ed9b1437
> Problems with generic types in Scala API
> ----------------------------------------
>
> Key: FLINK-1255
> URL: https://issues.apache.org/jira/browse/FLINK-1255
> Project: Flink
> Issue Type: Bug
> Components: Scala API
> Affects Versions: 0.7.0-incubating
> Reporter: Sebastian Schelter
> Assignee: Aljoscha Krettek
> Fix For: 0.9
>
>
> the code below produces the following exception:
> {noformat}
> Error:(47, 18) could not find implicit value for evidence parameter of type
> org.apache.flink.api.common.typeinfo.TypeInformation[K]
> data.groupBy { extractKey }
> {noformat}
> Fixing K to Long made the code run though
> {noformat}
> def groupCount[T, K](data: DataSet[T], extractKey: (T) => K): DataSet[(K,
> Long)] = {
> data.groupBy { extractKey }
> .reduceGroup { group => countBy(extractKey, group) }
> }
> private[this] def countBy[T, K](extractKey: T => K,
> group: Iterator[T]): (K, Long) = {
> val key = extractKey(group.next())
> var count = 1L
> while (group.hasNext) {
> group.next()
> count += 1
> }
> key -> count
> }
> {noformat}
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