Is it possible in SML to pattern match against a vector like you can with a list?

With a list I can simply do this:

```
fun foo ([]) = 0
  | foo (l::ls) = 1 + foo (ls);

```

How can I do that for a vector?

I tried `fun foo (Vector.fromList([])) = 0` but that gives me this error:

`Vector.fromList is not a constructor Found near Vector.fromList ([])`