Simplify graph tests by implicitly converting tuples to edges

Author: Abhijit Sarkar

graph/test/src/P83Spec.scala

@@ -4,10 +4,12 @@ import org.scalatest.funspec.AnyFunSpec
 import org.scalatest.matchers.should.Matchers.*
 import P83.spanningTrees
 import org.scalactic.Equality
+import graph.Util.given
+import scala.language.implicitConversions
 
 class P83Spec extends AnyFunSpec:
   it("construct all spanning trees"):
-    val data = List(
+    val data: List[(List[Char], List[Edge[Char, Nothing]])] = List(
       (
         List('a', 'b', 'c'),
         List(('a', 'b'), ('b', 'c'), ('a', 'c'))
@@ -30,16 +32,16 @@ class P83Spec extends AnyFunSpec:
       )
     )
 
-    val edgeEq = new Equality[(Char, Char)]:
-      def areEqual(a: (Char, Char), b: Any): Boolean =
+    val edgeEq = new Equality[Edge[Char, Nothing]]:
+      def areEqual(a: Edge[Char, Nothing], b: Any): Boolean =
         if b.isInstanceOf[List[?]] then
           b.asInstanceOf[List[Char]] match
-            case u :: v :: Nil => (u, v) == a || (v, u) == a
+            case u :: v :: Nil => (u, v) == (a.u, a.v) || (v, u) == (a.u, a.v)
             case _             => false
         else false
 
     data.foreach { (vertices, edges) =>
-      val g  = Graph.buildUG(vertices, edges.map((u, v) => Edge(u, v, None)))
+      val g  = Graph.buildUG(vertices, edges)
       val st = g.spanningTrees
       val n  = g.vertices.size
       st.foreach { t =>

graph/test/src/P84Spec.scala

@@ -4,10 +4,12 @@ import org.scalatest.funspec.AnyFunSpec
 import org.scalatest.matchers.should.Matchers.*
 import P84.minimalSpanningTree
 import org.scalactic.Equality
+import graph.Util.given
+import scala.language.implicitConversions
 
 class P84Spec extends AnyFunSpec:
   it("construct the minimal spanning tree"):
-    val data = List(
+    val data: List[(List[Char], List[Edge[Char, Int]], Int)] = List(
       (
         List('a', 'b', 'c'),
         List(('a', 'b', 1), ('b', 'c', 2), ('a', 'c', 3)),
@@ -32,15 +34,15 @@ class P84Spec extends AnyFunSpec:
       )
     )
 
-    val edgeEq = new Equality[(Char, Char, Int)]:
-      def areEqual(a: (Char, Char, Int), b: Any): Boolean =
+    val edgeEq = new Equality[Edge[Char, Int]]:
+      def areEqual(a: Edge[Char, Int], b: Any): Boolean =
         if b.isInstanceOf[Edge[?, ?]] then
-          val e = b.asInstanceOf[Edge[Char, Int]]
-          (a._1, a._2) == (e.u, e.v) || (a._1, a._2) == (e.v, e.u)
+          b.asInstanceOf[Edge[Char, Int]] match
+            case Edge(u, v, _) => (u, v) == (a.u, a.v) || (v, u) == (a.u, a.v)
         else false
 
     data.foreach { (vertices, edges, cost) =>
-      val g   = Graph.buildUG(vertices, edges.map((u, v, d) => Edge(u, v, Some(d))))
+      val g   = Graph.buildUG(vertices, edges)
       val mst = g.minimalSpanningTree
       mst.foreach(e => (edges should contain(e))(edgeEq))
       mst.foldLeft(0)((s, e) => s + e.data.getOrElse(0)) shouldBe cost

graph/test/src/P85Spec.scala

@@ -3,68 +3,76 @@ package graph
 import org.scalatest.funspec.AnyFunSpec
 import org.scalatest.matchers.should.Matchers.shouldBe
 import P85.isIsomorphicTo
+import graph.Util.given
+import scala.language.implicitConversions
 
 class P85Spec extends AnyFunSpec:
   it("graph isomorphism"):
 
-    val v1 = List('a', 'b')
-    val e1 = List(('a', 'b'))
-    val v2 = List(5, 7)
-    val e2 = List((5, 7))
-    val g1 = Graph.buildUG(v1, e1.map((u, v) => Edge(u, v, None)))
-    val g2 = Graph.buildUG(v2, e2.map((u, v) => Edge(u, v, None)))
+    val v1                            = List('a', 'b')
+    val e1: List[Edge[Char, Nothing]] = List(('a', 'b'))
+    val v2                            = List(5, 7)
+    val e2: List[Edge[Int, Nothing]]  = List((5, 7))
+    val g1                            = Graph.buildUG(v1, e1)
+    val g2                            = Graph.buildUG(v2, e2)
     g1.isIsomorphicTo(g2) shouldBe true
 
     // format: off
     val v3 = (1 to 8).toList
-    val e3 =
+    val e3: List[Edge[Int, Nothing]] =
       List(
         (1, 5), (1, 6), (1, 7), (2, 5),
         (2, 6), (2, 8), (3, 5), (3, 7),
         (3, 8), (4, 6), (4, 7), (4, 8)
       )
-    val e4 =
+    val e4: List[Edge[Int, Nothing]] =
       List(
         (1, 2), (1, 4), (1, 5), (6, 2),
         (6, 5), (6, 7), (8, 4), (8, 5),
         (8, 7), (3, 2), (3, 4), (3, 7)
       )
     // format: on
 
-    val g3 = Graph.buildUG(v3, e3.map((u, v) => Edge(u, v, None)))
-    val g4 = Graph.buildUG(v3, e4.map((u, v) => Edge(u, v, None)))
+    val g3 = Graph.buildUG(v3, e3)
+    val g4 = Graph.buildUG(v3, e4)
     g3.isIsomorphicTo(g4) shouldBe true
 
     val v5 = ('a' to 'e').toList
-    val e5 = List(('a', 'b'), ('a', 'c'), ('a', 'e'), ('b', 'c'), ('c', 'd'), ('d', 'e'))
+    val e5: List[Edge[Char, Nothing]] =
+      List(('a', 'b'), ('a', 'c'), ('a', 'e'), ('b', 'c'), ('c', 'd'), ('d', 'e'))
     val v6 = ('A' to 'E').toList
-    val e6 = List(('A', 'D'), ('A', 'E'), ('B', 'C'), ('B', 'D'), ('B', 'E'), ('C', 'D'))
+    val e6: List[Edge[Char, Nothing]] =
+      List(('A', 'D'), ('A', 'E'), ('B', 'C'), ('B', 'D'), ('B', 'E'), ('C', 'D'))
 
-    val g5 = Graph.buildUG(v5, e5.map((u, v) => Edge(u, v, None)))
-    val g6 = Graph.buildUG(v6, e6.map((u, v) => Edge(u, v, None)))
+    val g5 = Graph.buildUG(v5, e5)
+    val g6 = Graph.buildUG(v6, e6)
     g5.isIsomorphicTo(g6) shouldBe true
 
     val v7 = List('α', 'β', 'γ', 'δ', 'ε')
-    val e7 = List(('α', 'β'), ('α', 'γ'), ('α', 'ε'), ('β', 'δ'), ('γ', 'δ'), ('δ', 'ε'))
-    val g7 = Graph.buildUG(v7, e7.map((u, v) => Edge(u, v, None)))
+    val e7: List[Edge[Char, Nothing]] =
+      List(('α', 'β'), ('α', 'γ'), ('α', 'ε'), ('β', 'δ'), ('γ', 'δ'), ('δ', 'ε'))
+    val g7 = Graph.buildUG(v7, e7)
     g5.isIsomorphicTo(g7) shouldBe false
     g6.isIsomorphicTo(g7) shouldBe false
 
     val v8 = ('a' to 'f').toList
-    val e8 = List(('a', 'b'), ('a', 'd'), ('b', 'c'), ('c', 'f'), ('d', 'e'), ('e', 'f'))
-    val e9 = List(('a', 'd'), ('a', 'e'), ('b', 'd'), ('b', 'f'), ('c', 'e'), ('c', 'f'))
-    val g8 = Graph.buildUG(v8, e8.map((u, v) => Edge(u, v, None)))
-    val g9 = Graph.buildUG(v8, e9.map((u, v) => Edge(u, v, None)))
+    val e8: List[Edge[Char, Nothing]] =
+      List(('a', 'b'), ('a', 'd'), ('b', 'c'), ('c', 'f'), ('d', 'e'), ('e', 'f'))
+    val e9: List[Edge[Char, Nothing]] =
+      List(('a', 'd'), ('a', 'e'), ('b', 'd'), ('b', 'f'), ('c', 'e'), ('c', 'f'))
+    val g8 = Graph.buildUG(v8, e8)
+    val g9 = Graph.buildUG(v8, e9)
     g8.isIsomorphicTo(g9) shouldBe true
 
     // G(v8 e8) and G(va ea) are not isomorphic but the algorithm can't determine that.
     // val va = [1..6]
     // val ea = [(1, 3), (1, 5), (2, 4), (2, 6), (3, 5), (4, 6)]
 
     val v10 = ('A' to 'D').toList
-    val e10 = List(('A', 'B'), ('A', 'C'), ('A', 'D'), ('B', 'C'), ('B', 'D'), ('C', 'D'))
-    val v11 = (1 to 4).toList
-    val e11 = List((1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4))
-    val g10 = Graph.buildUG(v10, e10.map((u, v) => Edge(u, v, None)))
-    val g11 = Graph.buildUG(v11, e11.map((u, v) => Edge(u, v, None)))
+    val e10: List[Edge[Char, Nothing]] =
+      List(('A', 'B'), ('A', 'C'), ('A', 'D'), ('B', 'C'), ('B', 'D'), ('C', 'D'))
+    val v11                           = (1 to 4).toList
+    val e11: List[Edge[Int, Nothing]] = List((1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4))
+    val g10                           = Graph.buildUG(v10, e10)
+    val g11                           = Graph.buildUG(v11, e11)
     g10.isIsomorphicTo(g11) shouldBe true

graph/test/src/P86Spec.scala

@@ -3,10 +3,12 @@ package graph
 import org.scalatest.funspec.AnyFunSpec
 import org.scalatest.matchers.should.Matchers.*
 import P86.colorNodes
+import graph.Util.given
+import scala.language.implicitConversions
 
 class P86Spec extends AnyFunSpec:
   it("graph coloration"):
-    val data = List(
+    val data: List[(List[Char], List[Edge[Char, Nothing]])] = List(
       (
         ('a' to 'j').toList,
         List(
@@ -50,7 +52,7 @@ class P86Spec extends AnyFunSpec:
     )
 
     data.foreach { (vertices, edges) =>
-      val g      = Graph.buildUG(vertices, edges.map((u, v) => Edge(u, v, None)))
+      val g      = Graph.buildUG(vertices, edges)
       val clrMap = g.colorNodes.toMap
       vertices.foreach { u =>
         g.neighbors(u).map(v => clrMap(v._1)) should not contain (clrMap(u))

graph/test/src/Util.scala

@@ -0,0 +1,7 @@
+package graph
+
+object Util:
+  given [A, B] => Conversion[Tuple, Edge[A, B]] =
+    case (u, v)    => Edge(u.asInstanceOf[A], v.asInstanceOf[A], None)
+    case (u, v, d) => Edge(u.asInstanceOf[A], v.asInstanceOf[A], Some(d.asInstanceOf[B]))
+    case _         => throw IllegalArgumentException(s"unsupported tuple")