Go 基础学习 函数式编程

概述

• 函数式编程
  • 闭包
• 资源管理出错处理
  • defer调用 确保在函数结束时调用
  • defer 先入后出

代码

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)
    }
}

函数实现接口

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)
}