Getting the decimal part of a double in Swift

Question

I\'m trying to separate the decimal and integer parts of a double in swift. I\'ve tried a number of approaches but they all run into the same issue...

let x:         


        

Answer 1

You can get the Integer part like this:

let d: Double = 1.23456e12

let intparttruncated = trunc(d)
let intpartroundlower = Int(d)

The trunc() function truncates the part after the decimal point and the Int() function rounds to the next lower value. This is the same for positive numbers but a difference for negative numbers. If you subtract the truncated part from d, then you will get the fractional part.

func frac (_ v: Double) -> Double
{
    return (v - trunc(v))
}

You can get Mantissa and Exponent of a Double value like this:

let d: Double = 1.23456e78

let exponent = trunc(log(d) / log(10.0))

let mantissa = d / pow(10, trunc(log(d) / log(10.0)))

Your result will be 78 for the exponent and 1.23456 for the Mantissa.

Hope this helps you.

Answer 2

Without converting it to a string, you can round up to a number of decimal places like this:

let x:Double = 1234.5678
let numberOfPlaces:Double = 4.0
let powerOfTen:Double = pow(10.0, numberOfPlaces)
let targetedDecimalPlaces:Double = round((x % 1.0) * powerOfTen) / powerOfTen

Your output would be

0.5678

Answer 3

Swift 2:

You can use:

modf(x).1

or

x % floor(abs(x))