How Can Iterators Be Implemented in Go, and What Are Their Trade-offs?

Iterator Pattern in Go

The Iterator pattern is a design pattern that allows you to iterate over the elements in a collection without Exposes the underlying representation of the collection. There are several ways to create iterators in Go.

Channel

A channel is an iterator-like data structure. You can iterate over channels using the range keyword. However, its usage is limited when it turns out that this loop cannot be aborted without leaking the goroutine.

Closures

Closures are generally better suited than channels for creating iterators. It allows you to capture variables and create functions whose state persists between calls. You can use closures to create iterators that generate values.

func newEven() func() int {
    n := 0
    return func() int {
        n += 2
        return n
    }
}

Named Types

You can also use named types with methods to create iterators. This provides a more explicit and type-safe way to traverse collections.

type even int

func (e *even) next() int {
    *e += 2
    return int(*e)
}

Chained iterators

Chained iterators are easy to implement in Go because functions are first-class objects. You can use functions like map and filter to map or filter iterator values.

func mapInt(g intGen, f func(int) int) intGen {
    return func() int {
        return f(g())
    }
}

func square(i int) int {
    return i * i
}

Conclusion

There is no considered idiomatic way to create iterators in Go. You can choose the method that best suits your needs. Closures and named types are generally better suited for iterators that require state or chained behavior, while channels are better suited for one-shot traversal.

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