std/slice

import "std/slice" as slice;

Function	Result
isEmpty(values) Bool	Whether the slice has no elements
count(values) Int	Slice length
first(values) T	First element
last(values) T	Last element
at(values, index) T	Element after an explicit bounds check
setAt(values, index, value)	Assignment after an explicit bounds check
indexOf(values, needle) Int	First index, or -1
contains(values, needle) Bool	Whether the value occurs

fun total(values: []Int) Int {
    if slice.isEmpty(values) { return 0; }
    return slice.first(values) + slice.last(values);
}

first, last, at, and setAt call panic when their preconditions are not met.