initial permutation code

bewl2/src/main/scala/com/fdilke/bewl2/sets/morphenum/SetsGroupAssistant.scala

@@ -6,7 +6,8 @@ import com.fdilke.bewl2.sets.SetsUtilities.bulkJoin
 trait SetsGroupAssistant extends BaseSets:
   Ɛ: FindGroupActionGenerators =>
 
-  override protected val groupAssistant: GroupAssistant = LocalGroupAssistant
+  override protected val groupAssistant: GroupAssistant =
+    LocalGroupAssistant
 
   object LocalGroupAssistant extends GroupAssistant:
     def findCandidates[G, X, Y](group: Group[G])(

bewl2/src/main/scala/com/fdilke/bewl2/sets/permutations/Permutation.scala

@@ -1,8 +1,56 @@
 package com.fdilke.bewl2.sets.permutations
 
-class Permutation[T](
-  map: Map[T, T]
+class Permutation[A](
+  map: Map[A, A]
 ):
-  ()
+  def domain: Set[A] =
+    map.keySet
+  def apply(a: A): A =
+    map.get(a).getOrElse(
+      throw new IllegalArgumentException(s"key $a not found in map $map")
+    )
+
+class Cycle[A](
+  cycle: Seq[A]
+) {
+  if (cycle.toSet.size < cycle.length)
+    throw new IllegalArgumentException("cycle repeats")
+
+  def toMap: Map[A, A] =
+    val x: Seq[(A, A)] = cycle.indices.map { i =>
+      cycle(i) -> cycle( (i + 1) % cycle.length ) 
+    }
+    x.toMap[A, A]
+}
+
+class OngoingPermutation[A](
+  cycles: Seq[Cycle[A]]
+):
+  def toPermutation: Permutation[A] =
+    new Permutation(
+      cycles map { 
+        _.toMap
+      } reduce {
+        _ ++ _ 
+      }
+    )
+
+  def apply(a: A, tail: A*): OngoingPermutation[A] =
+    new OngoingPermutation(
+      cycles :+ Cycle(a +: tail)
+    )
+
+object Permutation:
+  def apply[A](a: A, tail: A*): OngoingPermutation[A] =
+    new OngoingPermutation(
+      Seq[Cycle[A]](
+        Cycle(a +: tail)
+      )
+    )
+
+  implicit def convertOngoing[A](
+    ongoing: OngoingPermutation[A]
+  ): Permutation[A] =
+    ongoing.toPermutation
 
 

bewl2/src/test/scala/com/fdilke/bewl2/sets/SetsUtilitiesSpec.scala

@@ -5,9 +5,7 @@ import munit.FunSuite
 import com.fdilke.bewl2.utility.RichFunSuite._
 import SetsUtilities.*
 import SetsWithSlowActions.*
-
 import scala.language.postfixOps
-
 import java.util.concurrent.atomic.AtomicBoolean
 
 class SetsUtilitiesSpec extends FunSuite:

bewl2/src/test/scala/com/fdilke/bewl2/sets/permutations/PermutationSpec.scala

@@ -2,6 +2,7 @@ package com.fdilke.bewl2.sets.permutations
 
 import munit.FunSuite
 import com.fdilke.bewl2.utility.RichFunSuite._
+import Permutation._
 
 class PermutationSpec extends FunSuite:
   test("Permutation can permute distinct objects in a cycle, and knows its domain"):