[Assorted-commits] SF.net SVN: assorted:[1798] sandbox/trunk/src/scala/FlatMap.scala

[<yan...@us...>]

Revision: 1798
          http://assorted.svn.sourceforge.net/assorted/?rev=1798&view=rev
Author:   yangzhang
Date:     2011-07-14 21:53:49 +0000 (Thu, 14 Jul 2011)

Log Message:
-----------
Add FlatMap exploration

Added Paths:
-----------
    sandbox/trunk/src/scala/FlatMap.scala

Added: sandbox/trunk/src/scala/FlatMap.scala
===================================================================
--- sandbox/trunk/src/scala/FlatMap.scala	                        (rev 0)
+++ sandbox/trunk/src/scala/FlatMap.scala	2011-07-14 21:53:49 UTC (rev 1798)
@@ -0,0 +1,40 @@
+// for deconstructing flatMap
+// try scala -Xprint:typer -Ytyper-debug
+
+object FlatMap extends App {
+  class XIterable[A](xs: TraversableOnce[A]) {
+    def izip[B](ys: TraversableOnce[B]) = xs.toIterator zip ys.toIterator
+  }
+  implicit def Iterable2XIterable[A](xs: TraversableOnce[A]) = new XIterable(xs)
+  implicit def Array2XIterable[A](xs: Array[A]) = new XIterable(xs)
+
+  {
+    val xss = Array(Array(0,1,2),Array(3,4,5))
+    val ys = Array(6,7,8)
+    for (xs <- xss.iterator; (x,y) <- xs.iterator zip ys.iterator) {
+      println((x,y))
+    }
+  }
+  /* desugars into:
+    xss.iterator.foreach( xs =>
+      xs.iterator.zip(ys.iterator).filter( pair =>
+        pair match {
+          case scala.Tuple2((x @ _), (y @ _)) => true
+          case _ => false
+        }
+      ).foreach( x =>
+        x match {
+          case scala.Tuple2((x @ _), (y @ _)) => println((x, y))
+        }
+      )
+    )
+  */
+
+  {
+    val xss = Array(Array(0,1,2),Array(3,4,5))
+    val ys = Array(6,7,8)
+    for (xs <- xss.iterator; (x,y) <- xs izip ys) {
+      println((x,y))
+    }
+  }
+}


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