Numbers
Swift contains three main number types: Int, Double, and Float.
Integers (Int)
By default, numbers without fractional components are inferred to be Ints:
let myNumber = 5 // Inferred to be of type Int
Ints cannot have decimal values:
let myNumber: Int = 5.75 // ❌ error: cannot convert value of type 'Double' to specified type 'Int'
Arithmetic can be performed on integers, but decimal values will be ignored and rounded down.
print(20 / 3) // 6 (not ~6.666666667)
print(9 / 4) // 2 (not 2.25)
print(100 / 99) // 1 (not ~1.01010101)
Doubles (Double)
Doubles are floating-point numbers that are represented as 64-bits. They are similar to Floats. By default, numbers with fractional components are usually inferred to be Doubles:
let myNumber = 5.0
Arithmetic can be performed on Doubles and is more accurate than arithmetic on Ints:
print(20.0 / 3.0) // 6.666666666666667
print(9.0 / 4.0) // 2.25
print(100.0 / 99.0) // 1.0101010101010102
Floats (Float)
Floats are floating-point numbers that are represented as 32-bits. They are similar to Doubles, but they take up less space and are less precise.
let myNumber: Float = 5.0
Converting between Int, Float, and Double
A Double can be converted to a Float, but precision may be lost:
let myDouble: Double = 834.4938247489
let myFloat = Float(myDouble)
print(myFloat) // 834.49384
A Float or Double can be converted to an Int but the fractional component is rounded down:
let myFloat = 9.999
let myInt = Int(myFloat)
print(myInt) // 9
An Int can be converted to a Float or Double:
let myInt = 5
print(Float(myInt)) // 5.0
print(Double(myInt)) // 5.0
