By Name Parameters

Author: CodeLab20

Functions/ByNameParameters.scala

@@ -0,0 +1,72 @@
+/**
+ * By Name parameters are parameters that can be called by block and lazily evaluated.
+ * By Name parameters are excellent for catching exception and cleaning up resources after you have done.
+ */
+
+object ByNameParameters extends App
+{
+  def byValue(x:Int)(y:Int) = {println("By Value:"); x + y}
+  
+  def byFunction(x:Int)(y: () => Int) = {println("By Function:"); x + y()}
+  
+  def byName(x:Int)(y: => Int) = {println("By Name:"); x + y}
+  
+  val a = byValue(3){
+                      println("In ByValue call..");
+                      19
+                    }    //this function will be evaluated first
+  
+  val b = byFunction(3)(() => {println("In ByFunction Call.."); 19}) // This line will be evaluated lazily. after call to byFunction
+  
+  val c = byName(3){
+                    println("In ByName call...");
+                    19
+                  }  //This line will be evaluated lazily.
+  
+   def divideSafely(f: =>Int):Option[Int] = {
+      try
+      {
+        Some(f)
+      }catch
+      {
+        case ae: ArithmeticException => None
+      }
+    
+  } 
+  
+  val d = divideSafely(
+      {
+        val x = 10
+        val y = 5
+        x / y
+        
+      })
+  
+  println("d = " + d)
+
+  val e = divideSafely(
+      {
+        val x = 10
+        val y = 0
+        x / y
+        
+      })
+  
+  println("e = " + e)
+ 
+  
+}
+
+/*
+Sample Output
+
+In ByValue call..
+By Value:
+By Function:
+In ByFunction Call..
+By Name:
+In ByName call...
+d = Some(2)
+e = None
+
+*/