additional code created during the meetup

README.md

@@ -3,8 +3,60 @@ implicitly-yours
 
 Sample Code for Dallas Scala Enthusiasts presentation
 
-## Building IDE files
-### Eclipse
+## The Slides
+### TL;DR [Slides here](https://gangstead.github.io/implicitly-yours)
+
+Since the default branch is gh-pages, go to http://gangstead.github.io/implicitly-yours to view the slides.
+
+To view the slides locally start a [static http server](https://gist.github.com/willurd/5720255) from that directory.  My preferred way:
+
+```
+# one time, to install the dependency
+> npm install -g http-server
+
+# start the server in the base directory. -o flag opens browser
+> http-server -o
+```
+
+## The Code
+### TL;DR `sbt run`
+### Running
+
+The sample code has multiple main classes.  From the command line type `sbt run` and you will get prompted to choose one:
+```
+gangstead$ sbt run
+[info] Loading global plugins from /Users/gangstead/.sbt/0.13/plugins
+[info] Loading project definition from /Users/gangstead/scala/implicitly-yours/project
+[info] Set current project to implicitly-yours (in build file:/Users/gangstead/scala/implicitly-yours/)
+[info] Compiling 3 Scala sources to /Users/gangstead/scala/implicitly-yours/target/scala-2.11/classes...
+[warn] Multiple main classes detected.  Run 'show discoveredMainClasses' to see the list
+
+Multiple main classes detected, select one to run:
+
+[1] gangstead.akka.main
+[2] gangstead.ImplicitlyImplicit
+[3] gangstead.ImplicitClassUseCase
+[4] gangstead.ImplicitParams
+[5] gangstead.ImplicitConversionUseCase
+
+Enter number: 2
+```
+If you want to make changes to the code and see compiler output in real time then use the command `sbt ~compile`
+
+```
+gangstead$ sbt ~compile
+[info] Loading global plugins from /Users/gangstead/.sbt/0.13/plugins
+[info] Loading project definition from /Users/gangstead/scala/implicitly-yours/project
+[info] Set current project to implicitly-yours (in build file:/Users/gangstead/scala/implicitly-yours/)
+[info] Compiling 3 Scala sources to /Users/gangstead/scala/implicitly-yours/target/scala-2.11/classes...
+[success] Total time: 7 s, completed Jan 9, 2015 12:32:05 PM
+1. Waiting for source changes... (press enter to interrupt)
+_
+```
+Now whenever you save a file sbt will recompile and display any warnings or errors.
+
+### Building IDE files
+#### Eclipse
 This project includes the plugin to generate Eclipse project files.  From the console:
 ```
 > sbt eclipse
@@ -19,19 +71,5 @@ Optionally if you want to include the sources of the dependencies:
 ```
 This will take longer in big projects, but this project is small.  I don't know why you can't just do `sbt eclipse with-source=true`.  That's what the plugin docs say, but it won't work for me.
 
-### IDEA
+#### IDEA
 Intellij IDEA can import SBT projects natively.
-
-
-## The Slides
-Since the default branch is gh-pages, go to http://gangstead.github.io/implicitly-yours to view the slides.
-
-To view the slides locally start a [static http server](https://gist.github.com/willurd/5720255) from that directory.  My preferred way:
-
-```
-# one time, to install the dependency
-> npm install -g http-server
-
-# start the server in the base directory. -o flag opens browser
-> http-server -o
-```

slides/slides.md

@@ -2,7 +2,8 @@ class: center, middle
 
 # implicitly yours
 ### Steven Gangstead
-### code and slides at https://github.com/gangstead/implicitly-yours
+### slides https://gangstead.github.io/implicitly-yours
+### code https://github.com/gangstead/implicitly-yours
 @Gangstead
 .footnote[.round[![:scale 20%](slides/credera.jpg)]]
 ---
@@ -145,7 +146,7 @@ implicit def toVeryEnthusiast(i : Int) = Enthusiast(i*10)
 
 - Extend classes that you can't otherwise modify
 - Reduce boilerplate code by having a bunch of conversions to one base class (aka [Magnet Pattern](http://spray.io/blog/2012-12-13-the-magnet-pattern/))
-- `enhancement(thing)` becomes `thing.enhancement` (just preference?)
+- `enhancement(thing)` becomes `thing.enhancement` (better encapsulation)
 ---
 # Implicit Classes
 ~~Pimping~~ Bedazzling originally of the form

src/main/scala/gangstead/ImplicitParams.scala

@@ -6,7 +6,7 @@ object ImplicitParams {
   //implicit val no: Int = -1 //can only have one implicit type match!
 
   def add(x: Int)(implicit y: Int) = x + y
-
+  //def add2(x: Int, implicit y: Int) = x + y //can't have just one param implicit
   def main(args: Array[String]) {
     println( add(5) ) 			// takes n from the current scope
     println( add(5) (1) )		//can always call explicitly

src/main/scala/gangstead/ImplicitlyImplicit.scala

@@ -3,6 +3,7 @@ package gangstead
 object ImplicitlyImplicit extends App {
 
   def basic() = {
+    println("\nbasic")
     implicit val n: Int = 5
 
     //def add(x: Int)(implicit y: Int) = x + y
@@ -13,17 +14,55 @@ object ImplicitlyImplicit extends App {
     println(add(5))
   }
 
+  /**
+  * From discussion in the meetup, there is a slight difference between
+  * using the implicit param and implicitly in the order of execution.
+  * The implicit parameter is evaluated when the method is called so
+  * if the implicit is a lazy val or a costly def the delay is incurred
+  * before the implicit is actually used.
+  */
+  def cornerCase() = {
+    println("\ncorner case")
+
+    implicit def n = { println("a") ; 10}
+
+    def add(x: Int) = {
+      println("b")
+      x + implicitly[Int]
+    }
+
+    def add2(x: Int)(implicit y: Int) = {
+      println("b")
+      x + y
+    }
+
+    println(add(5)) //b a 15
+    println(add2(5))// a b 15
+  }
+
+  /**
+  * If your function takes an implicit type the compiler can and will use a subtype
+  * It is legal to have a type and subtype in scope, the compiler will use the subtype.
+  * In this case we need a List[Any] and have List[Any], List[AnyVal] and List[Int] available.
+  * The List[Int] is a subtype of the other two.  If a List[Double] were available we'd get a compiler
+  * error because the compiler can't choose between the two.
+  */
   def subtypes() = {
+    println("\nsubtypes")
     //Most specific subtype whens
     def printList(implicit l: List[Any]) = l foreach println
 
     implicit val emptyList: List[Any] = Nil
+    implicit val anyValList: List[AnyVal] = List(1,2.0)
     implicit val intyList: List[Int] = List(1, 2, 3)
 
+    //implicit val doublyList: List[Double] = List(1.0,2.0,3.1) //ERROR. Double not a sub or parent type of Int.
+
     printList //1 2 3
   }
 
   def typeParams() = {
+    println("\ntypeparams")
     //type parameters implicitly
     implicit def emptyList[T]: List[T] = Nil
 
@@ -33,8 +72,10 @@ object ImplicitlyImplicit extends App {
 
   /**
    * source: http://www.drmaciver.com/2008/03/an-introduction-to-implicit-arguments/
+   * Advanced: Implicit def with an implicit parameter.
    */
   def doubleImplicit() = {
+    println("\ndouble implicit")
     case class Foo[T](t: T)
 
     implicit val hello = "Hello"
@@ -44,6 +85,7 @@ object ImplicitlyImplicit extends App {
   }
 
   basic()
+  cornerCase()
   subtypes()
   typeParams()
   doubleImplicit()