Difference between == and ===

Difference between == and ===

https://stackoverflow.com/questions/24002819/difference-between-and

== operator checks if their instance values are equal, "equal to”.  Value equality

=== operator checks if the references point the same instance, "identical to"  Reference equality

=== : Classes are reference types, it is possible for multiple constants and variables to refer to the same single instance of a class behind the scenes. 

let person1 = Person(ssn: 5, name: "Bob")

let person2 = Person(ssn: 5, name: "Bob")

if person1 == person2 {//We are checking values of that variables

   print("the two instances are equal!")

}

if person1 === person2 {//Reference types we are checking references here.

   //It does not enter here

} else {

   print("the two instances are not identical!")

}

=== operator checks if the references point the same instance, "identical to". Since person1 and person2 have two different instance in Heap area, they are not identical 

let person3 = person1

P.S: Classes are reference types and person1's reference is copied to person3 with this assignment operation, thus both references point the same instance in Heap area.

if person3 === person1 {

   print("the two instances are identical!")

}

Range Operators: 

Closed Range: 1…5 gives 1, 2, 3, 4 and 5

Half-Open Range: 1..< 5 gives 1, 2, 3, and 4

One- sided Range :  1… gives 1 , 2,3… end of elements.  ,  …2 gives beginning… to 1,2