Example of a Reflected function in Go 1.1

reflect_func_example

package main

import (
  "bufio"
	"bytes"
	"fmt"
	"io"
	"reflect"
	"runtime"
	"strings"
)

func say(writer func(string) (int, error), r io.Reader) error {
	s := bufio.NewScanner(r)
	s.Split(bufio.ScanWords)
	for n := 0; ; n++ {
		if !s.Scan() {
			writer(fmt.Sprintf("you said %d words.", n))
			return s.Err()
		}
		if _, err := writer(s.Text() + ", "); err != nil {
			return err
		}
	}
	// No return statement!
}

func main() {
	var buf bytes.Buffer
	defer fmt.Println(&buf)

	writeString := buf.WriteString
	say(writeString, strings.NewReader("why hello there "+runtime.Version()))

	var fn func(a, b string) int
	fv := reflect.ValueOf(&fn).Elem()
	fv.Set(reflect.MakeFunc(fv.Type(), func(in []reflect.Value) []reflect.Value {
		n := 0
		for _, v := range in {
			writeString(v.String())
			n++
		}
		return []reflect.Value{reflect.ValueOf(n)}
	}))
	n := fn(" and used ", "reflect.MakeFunc!")
	writeString(fmt.Sprintf(" (through which you printed %v strings ;-)", n))
}