merge_sort stability

[jesse99]

Don't see a unit test for that. Here is at least a basic test:

#[test]
fn test_merge_sort_stability()
{
    // not sure why we can't use just &
    pure fn ile(x: &@str, y: &@str) -> bool
    {
        unchecked            // to_lower is not pure...
        {
            let x = x.to_lower();
            let y = y.to_lower();
            x <= y
        }
    }

    let names1 = ~[@"joe bob", @"Joe Bob", @"Jack Brown", @"JOE Bob", @"Sally Mae", @"JOE BOB", @"Alex Andy"];
    let names2 = ~[@"Alex Andy", @"Jack Brown", @"joe bob", @"Joe Bob", @"JOE Bob", @"JOE BOB", @"Sally Mae"];
    let names3 = std::sort::merge_sort(ile, names1);
    assert names3 == names2;
}

[pcwalton]

(Regarding the comment: &&static/str should work, if you remove the @s from the arrays.)

[pcwalton]

to_lower and to_upper are pure now.