go 基礎7

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程式碼地址：

概述

• 函數語言程式設計

  • 閉包

• 資源管理出錯處理

  • defer呼叫 確保在函式結束時呼叫

  • defer 先入後出

程式碼

package main

import "fmt"

func adder() func(int) int {
	sum := 0
	return func(v int) int {
		sum += v
		return sum
	}
}

type iAdder func(int) (int, iAdder)

func adder2(base int) iAdder {
	return func(v int) (int, iAdder) {
		return base + v, adder2(base + v)
	}
}

func main() {
	// a := adder() is trivial and also works.
	a := adder2(0)
	for i := 0; i < 10; i++ {
		var s int
		s, a = a(i)
		fmt.Printf("0 + 1 + ... + %d = %d\n",
			i, s)
	}
}
 

函式實現介面

package main

import (
	"bufio"
	"fmt"
	"io"
	"strings"

	"golearn/functional/fib"
)

type intGen func() int

func (g intGen) Read(
	p []byte) (n int, err error) {
	next := g()
	if next > 10000 {
		return 0, io.EOF
	}
	s := fmt.Sprintf("%d\n", next)

	// TODO: incorrect if p is too small!
	return strings.NewReader(s).Read(p)
}

func printFileContents(reader io.Reader) {
	scanner := bufio.NewScanner(reader)

	for scanner.Scan() {
		fmt.Println(scanner.Text())
	}
}

func main() {
	var f intGen = fib.Fibonacci()
	printFileContents(f)
}