As of Go 1.23, the for ... := range ... syntax can now be used with "push-style" iterator functions. Since this package implements a different "pull-style" of iterators which are incompatible with the for ... := range ... syntax, I've decided to archive it. If you're looking for pull-style equivalents of some of the functions in this package, I'd recommend checking out the x/exp/iter package proposal.

iter

Package iter provides generic, lazy iterators, functions for producing them from primitive types, as well as functions and methods for transforming and consuming them.

Usage

package main

import (
	"fmt"
	"strings"

	"mtoohey.com/iter/v2"
)

func main() {
	initial := iter.Elems([]string{"hello", "beautiful", "world"})
	result := initial.Filter(func(s string) bool {
		return len(s) < 6
	}).Map(strings.ToUpper).Collect()
	fmt.Println(result) // produces: [HELLO WORLD]
}

Regarding Performance

There is some overhead to using the iterators in this package, since each evaluation requires a function call, so if the performance of your application is a top priority, this package might not be the best choice. Don't guess about performance though: I would recommend benchmarking to determine the impact of using iterators, because in some cases, lazy iterators may be faster than the equivalent strict loop.

Acknowledgements

• Everyone that commented on my r/golang post
• The inspiration for my own attempt: https://github.com/polyfloyd/go-iterator