Type inference

Type inference is the opposite of explicitly declaring the type of a variable. When using type inference, you simply omit the part telling the type of your variable and let the compiler guess it.

There are several ways for the compiler to guess the type of your variables. Let's see some of them!

Assigning a value

When you assign a value to a variable that still has an unknown type, its type will be inferred as being the one of the assigned value, so for example, if you write:

var s;s = "Hello World";

The type of s will be inferred to String.

Assigning the value of the variable to another one

In addition, if you assign the value of a variable that still has an unknown type to a variable that is of a known type, the type will also be inferred:

      var s;
      var t : String;
      t = s;

Here, the type of s is inferred to String.

Passing the variable as a parameter

When you pass a variable to a function, its type is inferred as being the one expected by the function. For example, consider...