+(_:_:)

The addition operator (+) calculates the sum of its two arguments. For example:

1 + 2                   // 3
-10 + 15                // 5
-15 + -5                // -20
21.5 + 3.25             // 24.75

You cannot use + with arguments of different types. To add values of different types, convert one of the values to the other value’s type.

let x: Int8 = 21
let y: Int = 1000000
Int(x) + y              // 1000021

The sum of the two arguments must be representable in the arguments’ type. In the following example, the result of 21 + 120 is greater than the maximum representable Int8 value:

x + 120                 // Overflow error

If you want to opt out of overflow checking and wrap the result in case of any overflow, use the overflow addition operator (&+).

x &+ 120                // -115