A pseudorandom number generator. (#56)

Introduces a new utility class `cgsuite.util.Random` that provides a pseudorandom number source.

Author: aaron-siegel

lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/lang/Collection.cgs

@@ -22,6 +22,12 @@ system class Collection
     */
   external def Concat(elements as Collection);
 
+  /** The number of elements of this `Collection` that match the
+    * specified predicate. `predicate` must be a [[Boolean]]-valued
+    * function.
+    */
+  external def Count(predicate as Function);
+
   /** `true` if there exists an element in this collection
     * that satisfies the given predicate.
     * `predicate` must be a [[Boolean]]-valued function.

lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/util/Random.cgs

@@ -0,0 +1,34 @@
+/*${cgsuite.banner}*/
+
+/** A pseudorandom number generator.
+  *
+  * To construct an instance of `Random`, specify an integer seed:
+  *
+  * \display{random := Random(1474)}
+  *
+  * Then use the [[#NextInteger]] method to generate output. This example produces integers `n` with `0 <= n < 100`:
+  *
+  * \display{random.NextInteger(100)}
+  *
+  * \display{[random.NextInteger(100) for n from 1 to 20]}
+  */
+mutable system class Random(
+  /** The seed for this `Random`. The seed must satisfy:
+    *
+    * `-2^63 <= seed < 2^63`
+    */
+  seed as Integer
+  )
+
+  /** The next `Integer` in this stream of pseudorandom numbers. The output `n` of `NextInteger(upperBound)` will always
+    * satisfy
+    *
+    * `0 <= n < upperBound`
+    *
+    * and will be (pseudo-)uniformly distributed within that range.
+    */
+  external def NextInteger(upperBound as Integer);
+
+  override def ToOutput := "Random(" + seed.ToOutput + ")";
+
+end

lib/core/src/main/scala/org/cgsuite/core/Integer.scala

@@ -87,12 +87,17 @@ trait Integer extends DyadicRationalNumber with GeneralizedOrdinal {
 
   def bigIntValue: BigInt
   override def intValue = {
-    if (bigIntValue.bigInteger.bitLength() <= 32)
+    if (bigIntValue.bigInteger.bitLength() < 32)
       bigIntValue.intValue
     else
       throw OverflowException("Overflow.")
   }
-  def longValue = bigIntValue.longValue
+  def longValue = {
+    if (bigIntValue.bigInteger.bitLength() < 64)
+      bigIntValue.longValue
+    else
+      throw OverflowException("Overflow.")
+  }
   def floatValue = bigIntValue.floatValue
   def doubleValue = bigIntValue.doubleValue
   def byteValue = bigIntValue.byteValue

lib/core/src/main/scala/org/cgsuite/lang/SpecialMethods.scala

@@ -3,7 +3,7 @@ package org.cgsuite.lang
 import org.cgsuite.core._
 import org.cgsuite.core.impartial.Spawning
 import org.cgsuite.exception.{EvalException, InvalidArgumentException, NotNumberException}
-import org.cgsuite.lang.CgscriptClass.SafeCast
+import org.cgsuite.lang.CgscriptClass.{SafeCast, internalize}
 import org.cgsuite.output.{ScatterPlotOutput, StyledTextOutput}
 import org.cgsuite.util.{Coordinates, Symmetry, Table}
 
@@ -72,6 +72,10 @@ object SpecialMethods {
 
     "cgsuite.lang.Collection.Adjoin" -> { (collection: Iterable[_], obj: Any) => collection ++ Iterable(obj) },
     "cgsuite.lang.Collection.Concat" -> { (collection: Iterable[_], that: Iterable[_]) => collection ++ that },
+    "cgsuite.lang.Collection.Count" -> { (collection: Iterable[_], fn: Function) =>
+      validateArity(fn, 1)
+      internalize(collection.count { x => fn.call(Array(x)).castAs[java.lang.Boolean] }.asInstanceOf[java.lang.Integer])
+    },
     "cgsuite.lang.Collection.Exists" -> { (collection: Iterable[_], fn: Function) =>
       validateArity(fn, 1)
       collection.exists { x => fn.call(Array(x)).castAs[java.lang.Boolean] }
@@ -168,10 +172,6 @@ object SpecialMethods {
 
   private val specialMethods2: Map[String, (_, _) => Any] = Map(
 
-    /*
-    "cgsuite.util.Graph.FromList" -> { (_: ClassObject, args: (IndexedSeq[Any], IndexedSeq[Any])) =>
-      Graph(args._1.map { _.asInstanceOf[IndexedSeq[Integer]] }, Option(args._2)) },
-     */
     "cgsuite.lang.List.Sublist" -> { (list: IndexedSeq[_], range: (Integer, Integer)) =>
       list.slice(range._1.intValue - 1, range._2.intValue)
     },

lib/core/src/main/scala/org/cgsuite/lang/SystemClassRegistry.scala

@@ -42,6 +42,7 @@ private[lang] object SystemClassRegistry {
 
     "cgsuite.util.Strip" -> classOf[Strip],
     "cgsuite.util.Grid" -> classOf[Grid],
+    "cgsuite.util.Random" -> classOf[Random],
     "cgsuite.util.Symmetry" -> classOf[Symmetry],
     "cgsuite.util.DirectedGraph" -> classOf[DirectedGraph[_, _]],
     "cgsuite.util.Edge" -> classOf[Graph.Edge[_]],

lib/core/src/main/scala/org/cgsuite/util/Random.scala

@@ -0,0 +1,23 @@
+package org.cgsuite.util
+
+import org.cgsuite.core.Integer
+import org.cgsuite.core.Values.one
+import org.cgsuite.exception.EvalException
+
+class Random(val seed: Integer) {
+
+  private val random = new scala.util.Random(seed.longValue)
+
+  def nextInteger(upperBound: Integer): Integer = {
+    if (upperBound < one) {
+      throw EvalException("Upper bound for `NextInteger` must be >= 1.")
+    }
+    val bits = (upperBound - one).lb.intValue + 1
+    var result: Integer = Integer(BigInt(bits, random))
+    while (result >= upperBound) {
+      result = Integer(BigInt(bits, random))
+    }
+    result
+  }
+
+}

lib/core/src/test/scala/org/cgsuite/lang/CgsuiteUtilTest.scala

@@ -73,4 +73,16 @@ class CgsuiteUtilTest extends CgscriptSpec {
 
   }
 
+  "cgsuite.util.Random" should "implement methods correctly" in {
+
+    executeTests(Table(
+      header,
+      ("Construct a Random", "random := Random(1474)", "Random(1474)"),
+      ("Random.NextInteger", "[random.NextInteger(100) for n from 1 to 20]",
+        "[64,92,17,25,63,58,88,49,0,30,85,46,58,24,72,31,98,61,61,69]"),
+      ("Random overflow", "Random(2^63)", "!!Overflow.")
+    ))
+
+  }
+
 }

lib/core/src/test/scala/org/cgsuite/lang/CollectionTestCase.scala

@@ -8,6 +8,7 @@ object CollectionTestCase {
       "[]", "[]",
       adjoin = "[19]",
       concat = "[10,*2]",
+      count = "0",
       exists = "false",
       flattened = "[]",
       forall = "true",
@@ -27,6 +28,7 @@ object CollectionTestCase {
       "[0,1,3,9,7,5]", "[0,1,3,9,7,5]",
       adjoin = "[0,1,3,9,7,5,19]",
       concat = "[0,1,3,9,7,5,10,*2]",
+      count = "2",
       exists = "true",
       flattened = "[0,1,3,9,7,5]",
       forall = "false",
@@ -46,6 +48,7 @@ object CollectionTestCase {
       """["Winning", "Ways", "Mathematical", "Plays"]""", """["Winning","Ways","Mathematical","Plays"]""",
       adjoin = """["Winning","Ways","Mathematical","Plays",19]""",
       concat = """["Winning","Ways","Mathematical","Plays",10,*2]""",
+      count = "!!No operation `>=` for arguments of types `cgsuite.lang.String`, `game.Integer`",
       exists = "false",
       flattened = """["Winning","Ways","Mathematical","Plays"]""",
       forall = "false",
@@ -70,6 +73,7 @@ case class CollectionTestCase(
   xOut: String,
   adjoin: String,
   concat: String,
+  count: String,
   exists: String,
   flattened: String,
   forall: String,
@@ -89,6 +93,7 @@ case class CollectionTestCase(
     (x, xOut),
     (s"($x).Adjoin(19)", adjoin),
     (s"($x).Concat([10,*2])", concat),
+    (s"($x).Count(x -> x >= 2 and x < 7)", count),
     (s"($x).Exists(x -> x == 7)", exists),
     (s"($x).Flattened", flattened),
     (s"($x).ForAll(x -> x == 7)", forall),