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Select the longest matching key in matchMap #179

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Jun 21, 2017
Merged

Select the longest matching key in matchMap #179

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706eca2
Select the longest matching key in matchMap
barnardb Mar 3, 2017
ecf2ea4
Select longest matching map key more efficiently
barnardb Jun 7, 2017
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6 changes: 3 additions & 3 deletions parboiled-core/src/main/scala/org/parboiled2/Parser.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -449,7 +449,7 @@ abstract class Parser(initialValueStackSize: Int = 16,
* THIS IS NOT PUBLIC API and might become hidden in future. Use only if you know what you are doing!
*/
def __matchMap(m: Map[String, Any]): Boolean = {
val keys = m.keysIterator
val keys = m.keys.toSeq.sortBy(-_.length).iterator
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I think we can actually make this more efficient.
We don't need to sort the whole map, only the prefix up until the match.
Check out this SO answer for an idea of how this could be done.

while (keys.hasNext) {
val mark = __saveState
val key = keys.next()
Expand All @@ -465,7 +465,7 @@ abstract class Parser(initialValueStackSize: Int = 16,
* THIS IS NOT PUBLIC API and might become hidden in future. Use only if you know what you are doing!
*/
def __matchMapWrapped(m: Map[String, Any]): Boolean = {
val keys = m.keysIterator
val keys = m.keys.toSeq.sortBy(-_.length).iterator
val start = _cursor
try {
while (keys.hasNext) {
Expand Down Expand Up @@ -670,4 +670,4 @@ object ParserMacros {

reify { ctx.Expr[RuleX](ruleTree).splice.asInstanceOf[Rule[I, O]] }
}
}
}
11 changes: 11 additions & 0 deletions parboiled-core/src/test/scala/org/parboiled2/BasicSpec.scala
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Expand Up @@ -168,6 +168,17 @@ class BasicSpec extends TestParserSpec {
"blue" must beMatchedWith(3)
"black" must beMismatched
}

"Map[String, T] with keys that prefix each other" in new TestParser1[Int] {
val colors = Map("a" -> 1, "ab" -> 2, "abc" -> 3, "abcd" -> 4, "abcde" -> 5, "abcdef" -> 6)
def targetRule = rule { colors ~ EOI }
"a" must beMatchedWith(1)
"ab" must beMatchedWith(2)
"abc" must beMatchedWith(3)
"abcd" must beMatchedWith(4)
"abcde" must beMatchedWith(5)
"abcdef" must beMatchedWith(6)
}
}

"The Parser" should {
Expand Down