Why GeneratorType have map method ？

[cache0928]

[cache0928]

I dont know the meaning of "generator = g.map(anyGenerator)" I cant run this code in playground

[justadreamer]

It's defined elsewhere as an extension on GeneratorType (f.e. see parsing.swift)

extension GeneratorType {
    mutating func map<B>(transform: Element -> B) -> AnyGenerator<B> {
        return anyGenerator {
            self.next().map(transform)
        }
    }
}