SML:从列表中删除条目 [英] SML: Remove the entry from the List

问题描述

如何删除列表L中的元素elem?如果列表不包含elem，则函数应返回不变的列表.

How can I delete the element elem in list L? If the list does not contain elem, then the function should return the list unchanged.

例如:

L = [1, 3, 4, 0, 5, 7]    
elem = 5

到目前为止，我具有以下功能:

So far I have the following function:

fun removeElem elem myList[] = myList
  | removeElem (myList::tl) = if mem myList elem then
                                rm elem myList[]
                              else
                                removeElem elem tl

推荐答案

您可以解决这个问题，并询问如何仅保留那些不等于elem的项目.这完全适合filter:

You can turn the question around and ask how to keep only those items not equal to elem. This fits cleanly with filter:

fun removeElem elem myList = filter (fn x => x <> elem) myList

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