[kotlin]Smart Cast & Any type in Kotlin

Smart Cast

In Kotlin, data types have the following meanings:

1) Define the size in which the object is stored
2) Whether objects are replaced or not. That is, they must have the same data type to execute.

For example, the operation of Int type and Double type is not performed.

val a: Int = 17
val b: Double= a
println(b)
     error: type mismatch: inferred type is Int but Double was expected
                  val b: Double= a

The assignment of a to object b is not done because the data types of objects a and b are different.
When using a data type to which a smart cast is applied, the data type is specified according to the assigned value.
The Number type is a data type to which a representative smart cast for numbers is applied.
Therefore, if the Number type is applied in the above case, it is as follows.

val a: Int = 17
val b: Number=a
println(b)
     17

In the code above, a is of type Int. For object b specified by Number, the data type is determined by the assigned value.

val a: Int = 17
var b: Number=a
println(b)
     17

b is Int
     res12: kotlin.Boolean = true

b=3.14
b
     res13: kotlin.Number = 3.14

b is Double
     res14: kotlin.Boolean = true

In the code above, b is a data type depending on the value passed to the object.

Any

"Any" is a data type that has the same process as smart cast.

"Any" is the superclass at the top of every class written by kotlin.
In other words, any class can inherit "Any".

As a result, variable declared as "Any" means that various kinds of values can be assigned.

var a: Any=3
a is Int
     res15: kotlin.Boolean = true

a=3.14
a is Double
     res16: kotlin.Boolean = true

a="kotlin"
a
     res17: kotlin.Any = kotlin
a is String
     res18: kotlin.Boolean = true