Code-Memo

Iterators, sequences, and generators

Go has no Python-style generators with yield. You express lazy sequences with functions returning channels, callbacks, iterators (Go 1.23+ range over functions), or plain slice indices.

Pull-style with channel (classic)

func ints(n int) <-chan int {
	ch := make(chan int)
	go func() {
		defer close(ch)
		for i := 0; i < n; i++ {
			ch <- i
		}
	}()
	return ch
}

Remember: channels are for communication; not every loop needs a goroutine.

Iterator functions (Go 1.23+)

The standard library adds iterator patterns (iter package). You can for v := range seq when seq yields values per the language spec. Check your Go version and go doc iter.

Manual iterator with closure

func readLines(next func() (string, bool)) {
	for {
		line, ok := next()
		if !ok {
			break
		}
		_ = line
	}
}

Range over built-ins

range on slices, maps, strings, and channels is the idiomatic iteration mechanism.

Performance note

Channel-based pipelines add synchronization overhead. For CPU-bound inner loops, prefer plain for with indices or slices/maps helpers (Go 1.21+).