combin_iterator/macros.rs
1/// The `altern!` macro provides a convenient syntax for creating an `Altern` iterator.
2///
3/// # Syntax
4///
5/// The macro takes a variable number of iterator expressions, separated by commas. It then constructs
6/// an `Altern` instance and adds each provided iterator using the `add` method.
7///
8/// # Example
9/// ```
10/// use combin_iterator::altern;
11/// let vec1 = vec![1, 4, 7, 9];
12/// let vec2 = vec![2, 5];
13/// let vec3 = vec![3, 6, 8];
14/// let iter = altern!(vec1.iter(), vec2.iter(), vec3.iter());
15///
16/// assert_eq!(iter.collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5, &6, &7, &8, &9]);
17/// ```
18///
19/// # Expand into
20///
21/// From the code before, altern! expand into:
22/// ```
23/// let vec1 = vec![1, 4, 7, 9];
24/// let vec2 = vec![2, 5];
25/// let vec3 = vec![3, 6, 8];
26/// let iter = {
27/// let capacity = 1 + (1 + (1 + 0));
28/// let mut vec_altern = combin_iterator::altern::VecAltern::with_capacity(
29/// capacity,
30/// );
31/// vec_altern.add(vec1.iter());
32/// vec_altern.add(vec2.iter());
33/// vec_altern.add(vec3.iter());
34/// vec_altern
35///};
36///
37/// assert_eq!(iter.collect::<Vec<_>>(), vec![&1, &2, &3, &4, &5, &6, &7, &8, &9]);
38/// ```
39#[macro_export]
40macro_rules! altern {
41 ($($params:expr $(,)?)*) => {
42 {
43 let capacity = $crate::count_exprs!($($params),*);
44 let mut vec_altern = $crate::altern::VecAltern::with_capacity(capacity);
45 $(
46 vec_altern.add($params);
47 )*
48 vec_altern
49 }
50 };
51}
52
53mod __private {
54 #[macro_export]
55 #[doc(hidden)]
56 macro_rules! count_exprs {
57 () => { 0 };
58 ($_head:expr $(, $tail:expr)*) => {
59 1 + $crate::count_exprs!($($tail),*)
60 };
61 }
62}
63
64
65#[cfg(test)]
66mod tests {
67 #[test]
68 fn macro_altern() {
69 let vec1 = vec![1, 4, 7, 9];
70 let vec2 = vec![2, 5];
71 let vec3 = vec![3, 6, 8];
72
73 let iter = altern!(vec1.iter(), vec2.iter(), vec3.iter());
74 assert_eq!(iter.collect::<Vec<_>>(), vec![&1,&2,&3,&4,&5,&6,&7,&8, &9]);
75 }
76}