Can data types defined as value types be modified?

In iOS (Swift), data types defined as value types (such as structures struct, enumerations enum, and basic types like Int, Double) are immutable by themselves if they are declared as constants (let). However, if a variable is declared with var, its values can be changed.

Example:

struct Point {
    var x: Int
    var y: Int
}

var p = Point(x: 0, y: 0)
p.x = 10  // Can be changed because p is a var

let p2 = Point(x: 1, y: 1)
// p2.x = 5  // Error because p2 is a let (constant)

Thus, the values of value types can be changed if the variable is not a constant. When passing a value type to a function or assigning it, a copy is created, and changes do not affect the original.