Doubles and booleans

Two other basic types of data in Swift are doubles and booleans, and you’ll be using them a lot.

“Double” is short for “double-precision floating-point number”, and it’s a fancy way of saying it holds fractional values such as 38.1, or 3.141592654.

Whenever you create a variable with a fractional number, Swift automatically gives that variable the type Double. For example:

var pi = 3.141

Doubles are different from integers, and you can’t mix them by accident.

As for booleans, they are much simpler: they just hold either true or false, and Swift will automatically assign the boolean type to any variable assigned either true or false as its value.

For example:

var awesome = true