个人网站支付解决方案,青岛网站seo多少钱,网站关键词工具有哪些,常见c2c网站有哪些从 A Tour of Go 可以看到一些 Go 比较特殊的点 文章目录 变量声明时#xff0c;类型放在后面Array 的引用 Slicereceiver 和 argumentbuilt-int特殊接口Error 变量声明时#xff0c;类型放在后面
var i, j int 1, 2declaration-syntax
Array 的引用 Slice
slices-intro …从 A Tour of Go 可以看到一些 Go 比较特殊的点 文章目录 变量声明时类型放在后面Array 的引用 Slicereceiver 和 argumentbuilt-int特殊接口Error 变量声明时类型放在后面
var i, j int 1, 2declaration-syntax
Array 的引用 Slice
slices-intro
receiver 和 argument
receiver 习惯用于改变值尤其是大的struct
type Vertex struct {X, Y float64
}func (v *Vertex) Scale(f float64) {v.X v.X * fv.Y v.Y * f
}argument 就是method的参数习惯用于业务逻辑
type Vertex struct {X, Y float64
}func AbsFunc(v Vertex) float64 {return math.Sqrt(v.X*v.X v.Y*v.Y)
}receiver 用于实现接口用于业务逻辑
type Abser interface {Abs() float64
}func main() {var a Abserv : Vertex{3, 4}a v // a *Vertex implements Abserfmt.Println(a.Abs())
}type Vertex struct {X, Y float64
}func (v *Vertex) Abs() float64 {return math.Sqrt(v.X*v.X v.Y*v.Y)
}built-int特殊接口Error
package mainimport (fmtmath
)type ErrNegativeSqrt float64func (x ErrNegativeSqrt) Error() string {return fmt.Sprintf(cannot Sqrt negative number: %f, x)
}func Sqrt2(x float64) (float64, error) {fmt.Println(processing.......)if x0 {z : float64(1)z 0.5fmt.Println(z)for i:0; math.Abs(z*z -x)0.00001; i {z z - (z*z -x )/(2*z)fmt.Println(i, i, z, z, z*z -x, z*z -x)}fmt.Println(finished.)return z, nil} else {return 0, ErrNegativeSqrt(x)}}func main() {fmt.Println(Sqrt2(2))fmt.Println(Sqrt2(-2))
}这里面如果在实现Error接口的时候调fmt.Sprintf用了%v会再次调x.Error() 进行无限循环, 如果用%v 的话先把值转换出来float64(x)
func (x ErrNegativeSqrt) Error() string {return fmt.Sprintf(cannot Sqrt negative number: %v, float64(x))
}查看golang源码 https://cs.opensource.google/go/go//refs/tags/go1.17:src/fmt/print.go;l617 // If were doing Go syntax and the argument knows how to supply it, take care of it now.if p.fmt.sharpV {if stringer, ok : p.arg.(GoStringer); ok {handled truedefer p.catchPanic(p.arg, verb, GoString)// Print the result of GoString unadorned.p.fmt.fmtS(stringer.GoString())return}} else {// If a string is acceptable according to the format, see if// the value satisfies one of the string-valued interfaces.// Println etc. set verb to %v, which is stringable.switch verb {case v, s, x, X, q:// Is it an error or Stringer?// The duplication in the bodies is necessary:// setting handled and deferring catchPanic// must happen before calling the method.switch v : p.arg.(type) {case error:handled truedefer p.catchPanic(p.arg, verb, Error)p.fmtString(v.Error(), verb)returncase Stringer:handled truedefer p.catchPanic(p.arg, verb, String)p.fmtString(v.String(), verb)return}}}return false
}A Tour of Go 习题解答
A Tour of Go 习题解答 2
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