Second attempt at snapping to angle intervals in Trgnmtry. This one works, and runs in linear time.

snapping-angle-second-attempt.swift

extension String {
    
    func indexOfClosestSorted(toValue value: Degree) -> Int {
        var smallestDifference = last!
        var closestIntervalAngleIdx = 0
        for i in 0 ..< count {
            let closestValueCandidate = self[i]
            var difference = fabs(closestValueCandidate - value)

            if difference == 0 {
                return i
            }

            if difference < 0 {
                difference *= -1
            }

            if difference < smallestDifference {
                smallestDifference = difference
                closestIntervalAngleIdx = i
            }
        }
        return closestIntervalAngleIdx
    }
    
}