用Haskell语言写出来

Certainly! Here's how you can define the `init` function in Haskell to remove the last element from a list:

Method 1: Using pattern matching and recursion

init' :: [a] -> [a]
init' [] = []
init' [x] = []
init' (x:xs) = x : init' xs

In this method, we define the `init'` function using pattern matching. The base cases handle empty lists and lists with only one element, returning an empty list. For lists with more than one element, we recursively remove the last element by appending the current element `x` to the result of `init' xs`.

Method 2: Using built-in functions

init'' :: [a] -> [a]
init'' = reverse . tail . reverse

In this method, we make use of built-in functions. We first reverse the list, then remove the first element using the `tail` function, and finally reverse the resulting list again. This effectively removes the last element from the original list.

Both methods achieve the same result of removing the last element from a list in Haskell. You can choose the method that best suits your needs or coding style.