Date: Mon, 23 Sep 2002 16:21:25 -0400 (EDT)
From: Li Liao <lliao@phobos.cis.udel.edu>


> Can you explain the built-in function
>   List.exists
> by giving example in ML syntax ?
>
> List.exists : ('a -> bool) -> 'a list -> bool
>
> What does it mean?

Function List.exists takes two arguments:
a function f (whose type is 'a -> bool)
and a list, say mylist (whose elements have type 'a).
List.exists will apply f to every element of mylist to see
if there exists an element x of mylist that satisfies f (namely
f x = true). If yes, List.exists return true, and false otherwise.

Example:

fun f x = if x = 1 then true else false;

val mylist = [2, 3, 4, 5]

List.exists f mylist;

val mylist' = [1, 2, 3, 4];

List.exists f mylist';

I hope this is helpful.

>
> I have done only first question. Can we submit the hw1 next week?

It is extended to next Tue. Please check the class bboard for the
anouncement.


Li