Simple example of implicit def.(REPL)

implicitDef.scala

scala> val a = "Jack"
a: String = Jack

scala> a.hello
<console>:9: error: value hello is not a member of String
              a.hello
                ^

scala> class B(s: String) {
     | def hello = "Hello " + s
     | }
defined class B

scala> val b = new B("Queen")
b: B = B@2d209079

scala> b.hello
res1: String = Hello Queen

scala> implicit def str2B(s: String) = new B(s)
warning: there was one feature warning; re-run with -feature for details
str2B: (s: String)B

scala> a.hello
res2: String = Hello Jack