递归函数加装饰器

decortor_with_recurive.go

package main

import "fmt"

type FibI interface {
	Fib(n int) int
	Wrap(fib FibI) FibI
}

type Fib struct {
	Wrapper FibI
}

func (this *Fib) Fib(n int) int {
	wrapper := this.Wrapper
	if this.Wrapper == nil {
		wrapper = this
	}
	if n == 0 {
		return 0
	}
	if n == 1 {
		return 1
	}
	// call son
	return wrapper.Fib(n-1) + wrapper.Fib(n-2)
}

func (this *Fib) Wrap(fib FibI) FibI {
	this.Wrapper = fib
	return this
}

type CacheFib struct {
	Wrapper FibI
	cache   map[int]int
}

func (this *CacheFib) Wrap(fib FibI) FibI {
	this.Wrapper = fib
	return this
}

func (this *CacheFib) Fib(n int) int {
	if this.cache == nil {
		this.cache = make(map[int]int)
	}
	if ans, ok := this.cache[n]; ok {
		return ans
	}
	ans := this.Wrapper.Fib(n)
	this.cache[n] = ans
	return ans
}

type CounterFib struct {
	Wrapper FibI
	Counter int
}

func (this *CounterFib) Wrap(fib FibI) FibI {
	this.Wrapper = fib
	return this
}

func (this *CounterFib) Fib(n int) int {
	this.Counter++
	return this.Wrapper.Fib(n)
}

func main() {
	fib := new(Fib)
	fmt.Println("result fib", fib.Fib(10))

	cacheFib := new(CacheFib)
	counterFib := new(CounterFib)
	counterCacheFib := cacheFib.Wrap(counterFib.Wrap(fib.Wrap(cacheFib)))
	fmt.Println("result cache:counter:fib", counterCacheFib.Fib(10))
	fmt.Printf("count: %d, cache: %v", counterFib.Counter, cacheFib.cache)
}

use globe variable

// use function program 
package main

import "fmt"

type FibI func(int) int

var Fib FibI

func init() {
	// use default one
	Fib = BaseFib()
}

func BaseFib() FibI {
	return func(n int) int {
		if n == 0 {
			return 0
		}
		if n == 1 {
			return 1
		}
		return Fib(n-1) + Fib(n-2)
	}
}

func CounterFib(counter *int, f FibI) FibI {
	return func(n int) int {
		*counter++
		return f(n)
	}
}

func CacheFib(cache map[int]int, f FibI) FibI {
	return func(n int) int {
		if ans, ok := cache[n]; ok {
			return ans
		}
		ans := f(n)
		cache[n] = ans
		return ans
	}
}

func main() {
	var counter int
	var cache = make(map[int]int)
	// change it to another one
	// however we cannot creat two different Fib function
	Fib = CacheFib(cache, CounterFib(&counter, BaseFib()))
	fmt.Println(Fib(10), counter, cache)
}