Binary operator '/' cannot be applied to two 'T' operands

Question

struct PickerRange<T: Comparable> {
    var start: T
    var end: T
    var step: T

    var length: T {
        // Binary operator '/' cannot be applied to two 'T' operands.
        return max(start, end) - min(start,end) / step 
    }
}

Error is generated when creating computed properties. How to fix?

Answer 1

Simply specify one of the Numeric protocols.

For floating point precision:

struct PickerRange<T:FloatingPoint> {
    var start: T
    var end: T
    var step: T

    var length: T {
        return max(start, end) -  (min(start,end) / step)
    }
}

SignedInteger, UnsignedInteger or other Numeric protocols are also an option.

// Comparable

Neither of these require of you to specify Comparable additionally, so specifying one of these is suffice for the case.

EDIT:

How to make one structure for Int and Double?

Essentially, you can, by specifying SignedNumeric:

struct PickerRange<T:SignedNumeric & Comparable> {
    var start: T
    var end: T
    var step: T
}

// Treated as PickerRange<Double>
let a = PickerRange(start: 1.0, end: 5.0, step: 1)

// Treated as PickerRange<Int>
let b = PickerRange(start: 1, end: 5, step: 1)

However, you have specialized length property, which includes / operator not supported by SignedNumeric. A workaround would consist in type-checking/force-casting to a type you have initialized your struct with:

struct PickerRange<T:SignedNumeric & Comparable> {
    var start: T
    var end: T
    var step: T

    var length: T {
        if T.self is Double.Type {
            return (max(start, end) as! Double) - ((min(start, end) as! Double) / (step as! Double)) as! T
        } else if T.self is Int.Type {
            return (max(start, end) as! Int) - ((min(start, end) as! Int) / (step as! Int)) as! T
        } else {
            return 0
        }
    }
}

let a = PickerRange(start: 1.0, end: 5.0, step: 1)
let b = PickerRange(start: 1, end: 10, step: 1)

print(a.length)
print(b.length)