Swift - Floating-Point Numbers


Floating-point numbers are numbers with fractional parts.

Examples of floating-point numbers are 0.0123, 2.45, and -4.521.

In Swift, there are two floating-point types: Float and Double.

Float uses 32 bits for storage and Double uses 64 bits.

This can be confirmed using the sizeof() function:


print("Size of Double: \(sizeof(Double)) bytes")
print("Size of Float: \(sizeof(Float)) bytes")

Double has a precision of at least 15 decimal digits, while Float has a precision of at least six decimal digits.

When assigning a floating-point number to a constant or variable, Swift will always infer the Double type unless you explicitly specify otherwise:


var num1 = 3.14           //num1 is Double
var num2: Float = 3.14    //num2 is Float

If you try to assign a Double to a Float type, the compiler will error out:

num2 = num1     //num1 is Double and num2 is Float

This is because the number stored in a Double type may not be able to fit into a Float type, and result in an overflow.

To assign num1 to num2 , explicitly cast num1 to a Float:

num2 = Float (num1)

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