Question

在JavaScript中，您可以加入一个字符串数组，例如：

fruits = ["orange", "apple", "banana"];
joined = fruits.join(", ");

console.log(joined)

// "orange, apple, banana"

你如何在ReasonML中做到这一点？

Answer 1

您可以使用Js.Array.joinWith：

let fruits = [|"orange", "apple", "banana"|];
let joined = Js.Array.joinWith(", ", fruits);
Js.log(joined);
// "orange, apple, banana"

Answer 2

将数组转换为连接值的字符串听起来像是Array.fold_left的作业，无论如何运行

Array.fold_left((a, b) => a ++ "," ++ b, "", fruits);

生产“，橙子，苹果，香蕉”。

理想情况下，fold（第二个参数）的起始值应该是数组中的第一个元素，而实际使用的数组将是其余元素，这样可以避免使用初始逗号。不幸的是，这对于数组来说并不容易，但是使用列表：

let fruitList = Array.to_list(fruits);
let joined = List.fold_left((a, b) => a ++ "," ++ b, List.hd(fruitList), List.tl(fruitList));
/*joined = "orange,apple,banana"*/

Reasonml docs on lists

Answer 3

以下是在ReasonML中实现自己的join函数的方法：

let rec join = (char: string, list: list(string)): string => {
  switch(list) {
  | [] => raise(Failure("Passed an empty list"))
  | [tail] => tail
  | [head, ...tail] => head ++ char ++ join(char, tail)
  };
};

有了这个，Js.log(join("$", ["a", "b", "c"]))就给了"a$b$c"，就像JavaScript一样。

加入字符串数组？

3 个答案: