SML - 一个小问题

Question

我已经给出：spacegather：string list - ＆gt;串

我必须创建一个函数，所以它会调用它：

spacegather [“I”，“am”，“nice”] to - ＆gt; “我很高兴”

感谢名单

Answer 1

intercalate xs xss = concat (intersperse xs xss)

找到插入的实际意义。这是散布的：

(*intersperse x [a,b,c..,z]=>[a,x,b,x,c,x..,x,z]*)

fun intersperse y  nil = nil
  | intersperse y [x] = [x]
  | intersperse y (x::xs)=x::y::(intersperse y xs)

Answer 2

让我看看我是否做对了：

fun spacegather (h::[]) = h 
| spacegather (h::tl) = h ^ " " ^ (spacegather tl);

spacegather ["I", "am", "nice!!"];

输出：val it =“我很好!!” ：string

这应该这样做，对吧？

Answer 3

String.concatWith " " ["I", "am", "nice"]