generators.go

package main

import (
	"fmt"
	"math/rand"
	"sync/atomic"
	"time"
)

func main() {
	r := Random(100)
	i := Increment(1)
	z := Zip(Random(50), Increment(20), Random(200))

	fmt.Println("random:", r(), r())
	fmt.Println("increment:", i(), i())
	fmt.Println("zip:", z(), z(), z(), z())
}

func Zip(generators ...func() int) func() int {
	if len(generators) == 0 {
		return nil
	}

	var idx int64

	return func() int {
		if int(idx) == len(generators) {
			idx = 0
		}
		f := generators[idx]
		atomic.AddInt64(&idx, 1)
		return f()
	}
}

func Random(border int) func() int {
	return func() int {
		rand.Seed(time.Now().UnixNano())
		n := rand.Intn(border)
		return n
	}
}

func Increment(val int) func() int {
	var counter int64

	return func() int {
		return int(atomic.AddInt64(&counter, int64(val)))
	}
}