Rewrote anonymous function syntax tour

Author: travissarles

Diff for: tutorials/tour/_posts/2017-02-13-anonymous-function-syntax.md

@@ -9,68 +9,36 @@ categories: tour
 num: 7
 next-page: higher-order-functions
 previous-page: mixin-class-composition
+prerequisite-knowledge: string-interpolation, expression-blocks
 ---
 
-Scala provides a relatively lightweight syntax for defining anonymous functions. The following expression creates a successor function for integers:
-
+Anonymous functions are functions which are not assigned to an identifier. On the left of the arrow `=>` is a parameter list, and on the right is an expression.
 ```tut
 (x: Int) => x + 1
 ```
 
-This is a shorthand for the following anonymous class definition:
-
-```tut
-new Function1[Int, Int] {
-  def apply(x: Int): Int = x + 1
-}
-```
+Anonymous functions are not very useful by themselves but they have a value which can be used as an argument of another function or the return value of another function. This will be covered later in the tour.
 
-It is also possible to define functions with multiple parameters:
+It is also possible to define functions with multiple parameters and/or an expression block:
 
 ```tut
-(x: Int, y: Int) => "(" + x + ", " + y + ")"
+(x: Int, y: Int) => {
+  val xSquared = x * x
+  val ySquared = y * y
+  s"($xSquared, $ySquared)"
+}
 ```
 
 or with no parameter:
 
 ```tut
-() => { System.getProperty("user.dir") }
+() => System.getProperty("user.dir")
 ```
 
-There is also a very lightweight way to write function types. Here are the types of the three functions defined above:
+The types of the three functions defined above are written like so:
 
 ```
 Int => Int
 (Int, Int) => String
 () => String
 ```
-
-This syntax is a shorthand for the following types:
-
-```
-Function1[Int, Int]
-Function2[Int, Int, String]
-Function0[String]
-```
-
-The following example shows how to use anonymous function of the beginning of this page
-
-```tut
-object AnonymousFunction {
-
-  /**
-   * Method to increment an integer by one.
-   */
-  val plusOne = (x: Int) => x + 1
-
-  /**
-   * Main method
-   * @param args application arguments
-   */
-  def main(args: Array[String]) {
-
-    println(plusOne(0)) // Prints: 1
-
-  }
-}
-```