Integer overflow and underflow

     In Swift, integer overflow and underflow occur when an integer value exceeds or falls below the maximum or minimum value that can be represented by its data type. 

Swift provides two types of integer data types: signed and unsigned. The signed integer data types can represent both positive and negative values, while the unsigned integer data types can only represent non-negative values. 

To understand integer overflow and underflow, consider the following example:

var myInt: Int8 = 120
myInt += 10 // This will cause an integer overflow

In this example, myInt is an 8-bit signed integer with a maximum value of 127. The += operator adds 10 to myInt, which causes an integer overflow, as the resulting value (130) exceeds the maximum value that can be represented by an 8-bit signed integer. As a result, myInt will have a value of -126, which is the minimum value that can be represented by an 8-bit signed integer.

 Similarly, consider the following example:

var myUInt: UInt8 = 0
myUInt -= 1 // This will cause an integer underflow

In this example, myUInt is an 8-bit unsigned integer with a minimum value of 0. The -= operator subtracts 1 from myUInt, which causes an integer underflow, as the resulting value (-1) falls below the minimum value that can be represented by an 8-bit unsigned integer. As a result, myUInt will have a value of 255, which is the maximum value that can be represented by an 8-bit unsigned integer. 

To prevent integer overflow and underflow, Swift provides the &+ and &- operators, which perform arithmetic operations and wrap-around the result if an overflow or underflow occurs. For example:

var myInt: Int8 = 120
myInt = myInt &+ 10 // This will wrap-around and set myInt to -126

In this example, the &+ operator adds 10 to myInt, but wraps around the result if an overflow occurs, resulting in myInt having a value of -126. Similarly, the &- operator subtracts a value and wraps around the result if an underflow occurs.