support scala 2.13.x

build.sbt

@@ -11,7 +11,7 @@ licenses      += ("BSD Simplified", url("https://opensource.org/licenses/BSD-3-C
 organizationName     := "CiBO Technologies, Inc."
 organizationHomepage := Some(url("https://www.cibotechnologies.com"))
 
-crossScalaVersions  := Seq("2.12.12")
+crossScalaVersions  := Seq("2.13.4", "2.12.12")
 scalaVersion        := crossScalaVersions.value.head
 
 sonatypeProjectHosting := Some(GitHubHosting("cibotech", "scalastan", "devops@cibotechnologies.com"))
@@ -40,3 +40,9 @@ libraryDependencies ++= Seq(
   "ch.qos.logback"             % "logback-classic"           % "1.2.3" % "test,it"
 )
 
+libraryDependencies ++= {
+  if (scalaVersion.value.startsWith("2.13."))
+    Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "1.0.2")
+  else
+    Seq()
+}

src/main/scala/com/cibo/scalastan/CompatParColls.scala

@@ -0,0 +1,17 @@
+package com.cibo.scalastan
+
+object CompatParColls {
+  val Converters = {
+    import Compat._
+
+    {
+      import scala.collection.parallel._
+
+      CollectionConverters
+    }
+  }
+
+  object Compat {
+    object CollectionConverters
+  }
+}

src/main/scala/com/cibo/scalastan/StanModel.scala

@@ -149,7 +149,7 @@ trait StanModel extends StanCodeBlock with StanContext { self =>
 
     private[scalastan] lazy val generate: StanFunctionDeclaration = StanFunctionDeclaration(
       result,
-      inputs,
+      inputs.toSeq,
       _code.results
     )
   }

src/main/scala/com/cibo/scalastan/StanProgramBuilder.scala

@@ -39,22 +39,22 @@ class StanProgramBuilder {
   // Leave the current scope (collapsing the statements collected using the specified function).
   def leave(f: Seq[StanStatement] => StanStatement): Unit = {
     require(stack.size > 1)
-    val result = f(stack.remove(stack.size - 1))
+    val result = f(stack.remove(stack.size - 1).toSeq)
     result.export(this)
     stack.last += result
   }
 
   // Special handling for "else if" statements.
   def handleElseIf(cond: StanValue[StanInt]): Unit = {
     cond.export(this)
-    val inside = stack.remove(stack.size - 1)
+    val inside = stack.remove(stack.size - 1).toSeq
     val ifStatement = stack.last.remove(stack.last.size - 1).asInstanceOf[StanIfStatement]
     stack.last += ifStatement.copy(ifStatement.conds :+ (cond, StanBlock(inside)))
   }
 
   // Special handling for "else" statements.
   def handleElse(): Unit = {
-    val inside = stack.remove(stack.size - 1)
+    val inside = stack.remove(stack.size - 1).toSeq
     val ifStatement = stack.last.remove(stack.last.size - 1).asInstanceOf[StanIfStatement]
     stack.last += ifStatement.copy(otherwise = Some(StanBlock(inside)))
   }
@@ -110,16 +110,16 @@ class StanProgramBuilder {
 
   lazy val results: StanBlock = {
     require(stack.size == 1)
-    StanBlock(stack.last)
+    StanBlock(stack.last.toSeq)
   }
 
   lazy val program: StanProgram = StanProgram(
-    dataValues,
-    parameterValues,
-    functions.map(_.generate),
-    transformedData.map(_.generate),
-    transformedParameters.map(_.generate),
-    generatedQuantities.map(_.generate),
+    dataValues.toSeq,
+    parameterValues.toSeq,
+    functions.map(_.generate).toSeq,
+    transformedData.map(_.generate).toSeq,
+    transformedParameters.map(_.generate).toSeq,
+    generatedQuantities.map(_.generate).toSeq,
     results
   )
 

src/main/scala/com/cibo/scalastan/StanResults.scala

@@ -11,8 +11,8 @@
 package com.cibo.scalastan
 
 import java.io.{PrintStream, PrintWriter}
-
 import com.cibo.scalastan.ast.{StanDataDeclaration, StanParameterDeclaration}
+import com.cibo.scalastan.CompatParColls.Converters._
 
 import scala.util.Try
 

src/main/scala/com/cibo/scalastan/StanType.scala

@@ -11,6 +11,7 @@
 package com.cibo.scalastan
 
 import com.cibo.scalastan.ast.{StanUnknownInt, StanValue}
+import com.cibo.scalastan.CompatParColls.Converters._
 
 sealed trait StanType {
 

src/main/scala/com/cibo/scalastan/analysis/StanAnalysis.scala

@@ -117,7 +117,7 @@ abstract class StanAnalysis[T](root: StanStatement) {
     val outLinks: Map[Int, Set[Int]] = getControlFlow(root)
     val inLinks: Map[Int, Set[Int]] = outLinks.toSeq.flatMap { case (parent, children) =>
       children.map(child => child -> parent)
-    }.groupBy(_._1).mapValues(vs => vs.map(_._2).toSet)
+    }.groupBy(_._1).mapValues(vs => vs.map(_._2).toSet).toMap
 
     val inputs: Map[Int, Set[Int]] = if (forward) inLinks else outLinks     // Inputs to a statement.
     val outputs: Map[Int, Set[Int]] = if (forward) outLinks else inLinks    // Outputs of a statement.

src/main/scala/com/cibo/scalastan/data/DataSource.scala

@@ -34,7 +34,7 @@ case class DataSource private[data] (
 ) {
 
   private lazy val raw: Map[String, DataValue] = rawSeq.map(v => v.name -> v).toMap
-  private lazy val reverseEnumerations: Map[String, Map[Int, String]] = enumerations.mapValues(_.map(_.swap).toMap)
+  private lazy val reverseEnumerations: Map[String, Map[Int, String]] = enumerations.mapValues(_.map(_.swap).toMap).toMap
 
   /** Get the names of the data values. */
   def names: Set[String] = raw.keySet

src/main/scala/com/cibo/scalastan/run/CmdStanRunner.scala

@@ -12,8 +12,8 @@ package com.cibo.scalastan.run
 
 import java.io._
 import java.nio.file._
-
 import com.cibo.scalastan._
+import com.cibo.scalastan.CompatParColls.Converters._
 import com.typesafe.scalalogging.LazyLogging
 
 import scala.collection.JavaConverters._
@@ -223,9 +223,9 @@ class CmdStanRunner(
       }
     }.seq
 
-    val parameterChains = results.flatMap(_.iterations).groupBy(_._1).mapValues(_.map(_._2))
+    val parameterChains = results.flatMap(_.iterations).groupBy(_._1).mapValues(_.map(_._2)).toVector
     val massMatrices = results.map(_.massMatrix)
-    StanResults(parameterChains, massMatrices, compiledModel, method)
+    StanResults(parameterChains.toMap, massMatrices, compiledModel, method)
   }
 }
 

src/test/scala/com/cibo/scalastan/ScalaStanBaseSpec.scala

@@ -35,7 +35,7 @@ trait ScalaStanBaseSpec extends FunSpec with Matchers {
       val mappedData: Map[String, Vector[Vector[Double]]] = data.flatten.groupBy(_._1).mapValues { grouped =>
         val iterations = grouped.map { case (k, v) => v }
         Vector.fill(chains)(iterations)
-      }
+      }.toMap
       StanResults(mappedData, Vector.empty, model, method)
     }
   }

src/test/scala/com/cibo/scalastan/StanResultsSpec.scala

@@ -47,7 +47,7 @@ class StanResultsSpec extends ScalaStanBaseSpec {
 
   val mappedData: Map[String, Vector[Vector[Double]]] = Seq(testData1, testData2).flatten.groupBy(_._1).mapValues(
     grouped => Vector(grouped.map{ case(k, v) => v }.toVector)
-  )
+  ).toMap
   val results = StanResults(mappedData, Vector.empty, model, RunMethod.Sample())
 
   describe("parameters") {