Watched talk from NSSpain Presenting Coordinators by Soroush Khanlou.

Reviewing code of my colleague learned that Swift provides two reduce functions on Sequence:

Use the reduce(_:_:) method to produce a single value from the elements of an entire sequence. For example, you can use this method on an array of numbers to find their sum or product.

Use the reduce(into:_:) method to produce a single value from the elements of an entire sequence. For example, you can use this method on an array of integers to filter adjacent equal entries or count frequencies.

Swift meetup question: trivial task for testing string if it contains only characters from valid character set. I know only one easy way to do this test - using inverted character set (below). But creating inverted character set seems to be not that cheap. Strange that String in Swift doesn’t provide such basic primitive operation.

let sample = "123"
let validCharacterSet = CharacterSet.decimalDigits
let notValidCharacterSet = validCharacterSet.inverted
let valid = sample.rangeOfCharacter(from: notValidCharacterSet) == nil