{"id":5306,"date":"2016-11-28T01:30:10","date_gmt":"2016-11-28T01:30:10","guid":{"rendered":"http:\/\/www.garysieling.com\/blog\/?p=5306"},"modified":"2016-11-28T01:30:10","modified_gmt":"2016-11-28T01:30:10","slug":"scala-recursively-calling-span","status":"publish","type":"post","link":"https:\/\/www.garysieling.com\/blog\/scala-recursively-calling-span\/","title":{"rendered":"Scala: recursively calling span"},"content":{"rendered":"

The span function in scala uses a predicate to break a list into two parts: the first elements matching the predicate, and the rest of the list.<\/p>\n

If you call this recursively, you can break the list up into pieces. <\/p>\n

In this case, we’ll take a list of tuples, which are words in a sentence, and their part of speech pairing.<\/p>\n

For words labeled as proper nouns, we want to find all the contiguous proper noun pairings, and print them out.<\/p>\n

\ntype WordPOS = (String, String)\ntype TaggedSentence = List[WordPOS]\ntype GroupedPOS = List[TaggedSentence]\n\ndef outersplitter(results: TaggedSentence): GroupedPOS = {\n  type SideBySideSentence = List[(WordPOS, WordPOS)]\n\n  val cmp: SideBySideSentence =\n    results.zip(\n      (\"\", \"\") :: results\n    )\n\n   def removeIndex( x:1<\/a><\/sup> = {\n    x._1\n  }\n\n  def splitter(results: SideBySideSentence): GroupedPOS = {\n    def next(cmp: List[2<\/a><\/sup>\n    }\n\n    val iter = next(results.zipWithIndex)\n    val first = iter._1.map(_._1)\n\n    val second: GroupedPOS =\n      iter._2 match {\n        case List() => {\n          List[TaggedSentence]()\n        }\n        case _ => {\n          val nextList = results.drop(iter._1.size)\n          splitter(nextList)\n        }\n      }\n\n    first :: second\n  }\n\n  splitter(cmp)\n}\n\nval sentencePairings = outersplitter(results)\n\nval possiblePeople =\n  sentencePairings.filter(\n    (aGrouping) => {\n      aGrouping.head._1 == \"NNP\"\n    }\n  ).map(\n    _.map(\n      _._2\n    ).mkString(\" \")\n  )\n<\/pre>\n
The real pain of the whole thing is that you need to track if you’re at the head of the list or not, when doing the span. <\/p>\n
If you can find a way to make this more compact, please let me know!<\/p>\n
  1.  WordPOS, WordPOS), Int  [↩<\/a>]<\/span><\/li>
  2. WordPOS, WordPOS), Int)]) = {\n      val res = cmp.span(\n        (pairings) => (pairings._1._1._1 == pairings._1._2._1 || pairings._2 == 0)\n      )\n\n      Tuple2(res._1.map(removeIndex), res._2.map(removeIndex [↩<\/a>]<\/span><\/li><\/ol>","protected":false},"excerpt":{"rendered":"
    Doing a ‘span’ in Scala to group matching continuous blocks of values in a list by a predicate<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[4],"tags":[385,480],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t