Another test pack for reflection

Also see https://github.com/scala/scala/pull/25.

1 files changed, 107 insertions, 0 deletions

diff --git a/test/pending/run/reify_fors.scala b/test/pending/run/reify_fors.scala
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+++ b/test/pending/run/reify_fors.scala
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+import scala.tools.nsc.reporters._
+import scala.tools.nsc.Settings
+import reflect.runtime.Mirror.ToolBox
+
+object Test extends App {
+  val code = scala.reflect.Code.lift{
+    object Persons {
+      /** A list of persons. To create a list, we use Predef.List
+       *  which takes a variable number of arguments and constructs
+       *  a list out of them.
+       */
+      val persons = List(
+        new Person("Bob", 17),
+        new Person("John", 40),
+        new Person("Richard", 68)
+      )
+
+      /** A Person class. 'val' constructor parameters become
+       *  public members of the class.
+       */
+      class Person(val name: String, val age: Int)
+
+      /** Return an iterator over persons that are older than 20.
+       */
+      def olderThan20(xs: Seq[Person]): Iterator[String] =
+        olderThan20(xs.elements)
+
+      /** Return an iterator over persons older than 20, given
+       *  an iterator over persons.
+       */
+      def olderThan20(xs: Iterator[Person]): Iterator[String] = {
+
+        // The first expression is called a 'generator' and makes
+        // 'p' take values from 'xs'. The second expression is
+        // called a 'filter' and it is a boolean expression which
+        // selects only persons older than 20. There can be more than
+        // one generator and filter. The 'yield' expression is evaluated
+        // for each 'p' which satisfies the filters and used to assemble
+        // the resulting iterator
+        for (p <- xs if p.age > 20) yield p.name
+      }
+    }
+
+    /** Some functions over lists of numbers which demonstrate
+     *  the use of for comprehensions.
+     */
+    object Numeric {
+
+      /** Return the divisors of n. */
+      def divisors(n: Int): List[Int] =
+        for (i <- List.range(1, n+1) if n % i == 0) yield i
+
+      /** Is 'n' a prime number? */
+      def isPrime(n: Int) = divisors(n).length == 2
+
+      /** Return pairs of numbers whose sum is prime. */
+      def findNums(n: Int): Iterable[(Int, Int)] = {
+
+        // a for comprehension using two generators
+        for (i <- 1 until n;
+             j <- 1 until (i-1);
+             if isPrime(i + j)) yield (i, j)
+      }
+
+      /** Return the sum of the elements of 'xs'. */
+      def sum(xs: List[Double]): Double =
+        xs.foldLeft(0.0) { (x, y) => x + y }
+
+      /** Return the sum of pairwise product of the two lists. */
+      def scalProd(xs: List[Double], ys: List[Double]) =
+        sum(for((x, y) <- xs zip ys) yield x * y);
+
+      /** Remove duplicate elements in 'xs'. */
+      def removeDuplicates[A](xs: List[A]): List[A] =
+        if (xs.isEmpty)
+          xs
+        else
+          xs.head :: removeDuplicates(for (x <- xs.tail if x != xs.head) yield x)
+    }
+
+    // import all members of object 'persons' in the current scope
+    import Persons._
+
+    print("Persons over 20:")
+    olderThan20(persons) foreach { x => print(" " + x) }
+    println
+
+    import Numeric._
+
+    println("divisors(34) = " + divisors(34))
+
+    print("findNums(15) =")
+    findNums(15) foreach { x => print(" " + x) }
+    println
+
+    val xs = List(3.5, 5.0, 4.5)
+    println("average(" + xs + ") = " + sum(xs) / xs.length)
+
+    val ys = List(2.0, 1.0, 3.0)
+    println("scalProd(" + xs + ", " + ys +") = " + scalProd(xs, ys))
+  };
+
+  val reporter = new ConsoleReporter(new Settings)
+  val toolbox = new ToolBox(reporter)
+  val ttree = toolbox.typeCheck(code.tree)
+  toolbox.runExpr(ttree)
+}