'Float' is not convertible to 'UInt8' in Swift

Question

I receive a type-related error ( 'Float' is not convertible to 'UInt8' ) while using the following formula in Swift. Although I've seen posts with similar questions, I can't seem to figure out why, in this case, the conversion to UInt8 is occurring in the first place and how to fix the type conversion error. I'm a newcomer to the language.

func compoundInterest (principal p: Float, interestRate r: Float,
    timesCompounded n: Int, years t: Int) -> Float {
        return p * pow(1 + (r / n), n * t)
}

compoundInterest(principal: 150, interestRate: 0.05, timesCompounded: 2, years: 10)

Answer 1

The error message is misleading but the problem is that Swift doesn't do implicit type conversions — just to pull one part of your expression out:

r / n

r is a floating point type. n is an integer type. In C the promotion rules would implicitly concert n to a float. That doesn't happen in Swift.

You probably want explicitly to cast all your integer types to Float to resolve the issue.