Go 1.23 New Features: range-over-func Finally Here

Simi included in Go

2025-12-20 116 words One minute

Contents

range-over-func Officially Available

        
        
        
    
// can do lazy collection without channel
func Range(start, end int) func(yield func(int) bool) {
    return func(yield func(int) bool) {
        for i := start; i < end; i++ {
            if !yield(i) {
                return
            }
        }
    }
}

func main() {
    for v := range Range(0, 10) {
        fmt.Println(v)
    }
}

iterators Package

        
        
        
    
import "iter"

func First[T any](seq iter.Seq[T]) (T, bool) {
    for v := range seq {
        return v, true
    }
    var zero T
    return zero, false
}

Practical Value

range-over-func good for:

processing large datasets (don’t need to load all in memory)
infinite sequences
pipeline-style data processing

Conclusion

Go 1.23 has no revolutionary changes, but range-over-func formalization is an important engineering advancement.