add maxBefore and minAfter

compat/src/main/scala-2.11_2.12/scala/collection/compat/PackageShared.scala

@@ -305,6 +305,14 @@ private[compat] trait PackageShared {
       fact: Sorted[K, V]): SortedExtensionMethods[K, V] =
     new SortedExtensionMethods[K, V](fact)
 
+  implicit def toSortedMapExtensionMethods[K, V](
+      fact: collection.SortedMap[K, V]): SortedMapExtensionMethods[K, V] =
+    new SortedMapExtensionMethods[K, V](fact)
+
+  implicit def toSortedSetExtensionMethods[A](
+      fact: collection.SortedSet[A]): SortedSetExtensionMethods[A] =
+    new SortedSetExtensionMethods[A](fact)
+
   implicit def toIteratorExtensionMethods[A](self: Iterator[A]): IteratorExtensionMethods[A] =
     new IteratorExtensionMethods[A](self)
 
@@ -401,6 +409,24 @@ class SortedExtensionMethods[K, T <: Sorted[K, T]](private val fact: Sorted[K, T
   def rangeUntil(until: K): T = fact.until(until)
 }
 
+class SortedMapExtensionMethods[K, V](
+    private val self: collection.SortedMap[K, V]
+) extends AnyVal {
+
+  def minAfter(key: K): Option[(K, V)] = self.from(key).headOption
+
+  def maxBefore(key: K): Option[(K, V)] = self.until(key).lastOption
+}
+
+class SortedSetExtensionMethods[A](
+    private val self: collection.SortedSet[A]
+) extends AnyVal {
+
+  def minAfter(key: A): Option[A] = self.from(key).headOption
+
+  def maxBefore(key: A): Option[A] = self.until(key).lastOption
+}
+
 class IteratorExtensionMethods[A](private val self: c.Iterator[A]) extends AnyVal {
   def sameElements[B >: A](that: c.TraversableOnce[B]): Boolean = {
     self.sameElements(that.iterator)

compat/src/test/scala/test/scala/collection/SortedTest.scala

@@ -64,4 +64,48 @@ class SortedTest {
     }
      */
   }
+
+  @Test
+  def sortedSetMinAfter(): Unit = {
+    val values = 1 to 10
+    assertEquals(values.to(collection.SortedSet).minAfter(8), Some(8))
+    assertEquals(values.to(collection.immutable.SortedSet).minAfter(9), Some(9))
+    assertEquals(values.to(collection.mutable.SortedSet).minAfter(10), Some(10))
+
+    assertEquals(values.to(collection.SortedSet).minAfter(11), None)
+    assertEquals(values.to(collection.immutable.SortedSet).minAfter(12), None)
+    assertEquals(values.to(collection.mutable.SortedSet).minAfter(13), None)
+  }
+
+  @Test
+  def sortedSetMaxBefore(): Unit = {
+    val values = 1 to 10
+    assertEquals(values.to(collection.SortedSet).maxBefore(4), Some(3))
+    assertEquals(values.to(collection.immutable.SortedSet).maxBefore(3), Some(2))
+    assertEquals(values.to(collection.mutable.SortedSet).maxBefore(2), Some(1))
+
+    assertEquals(values.to(collection.SortedSet).maxBefore(1), None)
+    assertEquals(values.to(collection.immutable.SortedSet).maxBefore(0), None)
+    assertEquals(values.to(collection.mutable.SortedSet).maxBefore(-1), None)
+  }
+
+  @Test
+  def sortedMapMinAfter(): Unit = {
+    val values = (1 to 10).map(x => x -> x.toString)
+    assertEquals(collection.SortedMap(values: _*).minAfter(9), Some(9 -> "9"))
+    assertEquals(collection.immutable.SortedMap(values: _*).minAfter(10), Some(10 -> "10"))
+
+    assertEquals(collection.SortedMap(values: _*).minAfter(11), None)
+    assertEquals(collection.immutable.SortedMap(values: _*).minAfter(12), None)
+  }
+
+  @Test
+  def sortedMapMaxBefore(): Unit = {
+    val values = (1 to 10).map(x => x -> x.toString)
+    assertEquals(collection.SortedMap(values: _*).maxBefore(3), Some(2 -> "2"))
+    assertEquals(collection.immutable.SortedMap(values: _*).maxBefore(2), Some(1 -> "1"))
+
+    assertEquals(collection.SortedMap(values: _*).maxBefore(1), None)
+    assertEquals(collection.immutable.SortedMap(values: _*).maxBefore(0), None)
+  }
 }