rbrockerhoff

Pre-proposal: Safer Decimal Calculations

• Proposal: TBD
• Author(s): Rainer Brockerhoff
• Status: TBD
• Review manager: TBD

Quoting the “The Swift Programming Language” book: “Swift adopts safe programming patterns…”; “Swift is friendly to new programmers”. The words “safe” and “safety” are found many times in the book and in online documentation. The usual rationale for safe features is, to quote a typical sentence, “…enables you to catch and fix errors as early as possible in the development process”.

One frequent stumbling point for both new and experienced programmers stems from the vagaries of binary floating-point arithmetic. This tentative pre-proposal suggests one possible way to make the dangers somewhat more clear.

rbrockerhoff

extension Dictionary {
	mutating func merge <S: Sequence where S.GeneratorType.Element == Element> (seq: S) {
		var gen = seq.generate()
		while let (key: KeyType, value: ValueType) = gen.next() {
			self[key] = value
		}
	}
}

var dict = [0:0]

rbrockerhoff

extension Dictionary {
	init (_ array: Array<Element>) {
		self = [ : ]
		self.merge(array)
	}
	
	mutating func merge (array: Array<Element>) {
		for (key: KeyType, value: ValueType) in array {
			self[key] = value
		}