Demonstrate implicit in Scala

implicit.scala

/*******************************/
/***** Implicit conversion *****/
/*******************************/

// If one calls a method m on an object o of a class C, and that class does not support method m, 
// then Scala will look for an implicit conversion from C to something that does support m.

// Use to automatically convert a value from one type to another
val value:BigInt = 1
// What actually happened is:
val value:BigInt = math.BigInt.int2bigInt(1)
// This is done by the scala compiler, it finds an implicit function that can convert Int to BigInt in its current scope:
implicit def int2bigInt(i: Int): BigInt = apply(i)

/*******************************/
/***** Implicit parameters *****/
/*******************************/

// The final parameter list on a method can be marked implicit, which means the values will be taken from the context in which they are called. 
// If there is no implicit value of the right type in scope, it will not compile. 
// Since the implicit value must resolve to a single value and to avoid clashes, it's a good idea to make the type specific to its purpose

class Prefixer(val prefix: String)

def addPrefix(s: String)(implicit p: Prefixer) = p.prefix + s

implicit val myImplicitPrefixer = new Prefixer("***")
addPrefix("abc")  // returns "***abc"