2 files changed, 68 insertions(+), 0 deletions(-)

M env/src/main.rs
A env/src/pairing.rs

@@ 1,4 1,5 @@
 pub mod fitness;
+pub mod pairing;
 pub mod crossover;
 pub mod bounded;
 pub mod selection;

@@ 0,0 1,67 @@
+use std::marker::PhantomData;
+
+use crate::replacement::EvaluatedPopulation;
+
+pub type ParentPairing = (usize, usize);
+
+pub trait Pairing {
+    type Chromosome;
+    type Out;
+
+    fn pair<T: Iterator<Item = usize>>(
+        &mut self,
+        population: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        parents: T
+    ) -> impl Iterator<Item = ParentPairing>;
+}
+
+pub struct AdjacentPairing<TChromosome, TOutput> {
+    _phantom1: PhantomData<TChromosome>,
+    _phantom2: PhantomData<TOutput>,
+}
+
+impl<TChromosome, TOutput> AdjacentPairing<TChromosome, TOutput> {
+    pub fn new() -> Self {
+        Self {
+            _phantom1: PhantomData,
+            _phantom2: PhantomData,
+        }
+    }
+}
+
+impl<TChromosome, TOutput> Pairing for AdjacentPairing<TChromosome, TOutput> {
+    type Chromosome = TChromosome;
+    type Out = TOutput;
+
+    fn pair<T: Iterator<Item = usize>>(
+        &mut self,
+        _: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        parents: T
+    ) -> impl Iterator<Item = ParentPairing> {
+        AdjacentIterator(parents, 0)
+    }
+}
+
+pub struct AdjacentIterator<T: Iterator<Item = usize>>(T, usize);
+
+impl<T: Iterator<Item = usize>> Iterator for AdjacentIterator<T> {
+    type Item = ParentPairing;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let first = self.0.next();
+        let second = self.0.next();
+
+        match (first, second) {
+            // Still two elements left, return them
+            (Some(first), Some(second)) => {
+                self.1 = second; // Save previous
+                Some((first, second))
+            },
+            // Only one element remaining, return it and the previous one
+            (Some(first), _) => Some((first, self.1)),
+            (None, Some(_)) => panic!("Iterators cannot return something after they return none."),
+            // No more elements
+            _ => None
+        }
+    }
+}