add skip odd even

src/rule/collection/skip/option.rs

@@ -1,8 +1,12 @@
 mod no_skip;
+mod skip_even_index;
 mod skip_first;
+mod skip_odd_index;
 
 pub use no_skip::NoSkip;
+pub use skip_even_index::SkipEvenIndex;
 pub use skip_first::SkipFirst;
+pub use skip_odd_index::SkipOddIndex;
 
 pub trait SkipOption {
     type Item;

src/rule/collection/skip/option/skip_even_index.rs

@@ -0,0 +1,13 @@
+use crate::rule::SkipOption;
+
+pub struct SkipEvenIndex<ITEM> {
+    _phantom_data: std::marker::PhantomData<ITEM>,
+}
+
+impl<ITEM> SkipOption for SkipEvenIndex<ITEM> {
+    type Item = ITEM;
+    type Accumulator = ();
+    fn should_skip(i: usize, _: Option<&mut Self::Accumulator>, _: &Self::Item) -> bool {
+        i % 2 == 0
+    }
+}

src/rule/collection/skip/option/skip_odd_index.rs

@@ -0,0 +1,13 @@
+use crate::rule::SkipOption;
+
+pub struct SkipOddIndex<ITEM> {
+    _phantom_data: std::marker::PhantomData<ITEM>,
+}
+
+impl<ITEM> SkipOption for SkipOddIndex<ITEM> {
+    type Item = ITEM;
+    type Accumulator = ();
+    fn should_skip(i: usize, _: Option<&mut Self::Accumulator>, _: &Self::Item) -> bool {
+        i % 2 == 1
+    }
+}