1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44

#![no_std]

pub mod seq;

/// The identity function.
///
/// Literally, just returns the passed-in value.
pub fn id<T>(value: T) -> T { value }

/// Return a default value.
pub fn default<T: Default>() -> T {
    Default::default()
}

/// Get the first element of a sequence with at least one element.
pub fn first<P: seq::Singleton>(seq: P) -> P::First {
    seq.first()
}

/// Get the second element of a sequence with at least to elements
pub fn second<P: seq::Pair>(seq: P) -> P::Second {
    seq.second()
}

/// Get the third element of a sequence with at least three elements.
pub fn third<P: seq::Triple>(seq: P) -> P::Third {
    seq.third()
}

// TODO: Generic?
/// Flip a length two tuple.
pub fn flip<A, B>((a, b): (A, B)) -> (B, A) {
    (b, a)
}

#[test]
fn test_seq() {
    assert_eq!(first((1, 2)), 1);
    assert_eq!(first(&(1, 2)), &1);
    assert_eq!(second((1, 2)), 2);
    assert_eq!(third(&[] as &[i32]), None);
    assert_eq!(second(&[1,2][..]), Some(&2));
    assert_eq!(second(&[1,2]), &2);
}