メソッドチェーン可能な設計のstructを拡張するには - Qiita// https://play.golang.org/p/2-eVlADzDu package main import ( "fmt" "container/list" ) type Element struct { *list.Element } func enhanceElement(e *list.Element) *Element { return &Element{e} } func (e *Element) Advance(n int) *Element { if n == 0 { return e } forward := n > 0 if !forward { n = -n } r := e for i := 0; i < n; i++ { if forward { r = enhanceElement(r.Next()) } else { r = enhanceEleme
