From 06f3259b7694559e224c43dac7a4fcf200762721 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Sun, 5 Oct 2025 20:12:29 +0200
Subject: [PATCH] feat: add BoundedPerturbation

applies bounds on real numbers when performing the perturbation.
---
 env/src/perturbation/mod.rs | 76 +++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/env/src/perturbation/mod.rs b/env/src/perturbation/mod.rs
index 25e202cda3db32995312908f2638289ca49bf54a..df04b6377949baa43ea0eb1a9e9eb4cfadd8b90e 100644
--- a/env/src/perturbation/mod.rs
+++ b/env/src/perturbation/mod.rs
@@ -54,6 +54,82 @@ impl<TRng: Rng, TDistribution: Distribution<f64>, const LEN: usize> Perturbation
     }
 }
 
+pub enum BoundedPerturbationStrategy {
+    /// Trims the value to get a value within bounds
+    Trim,
+    /// Retries calling the underlying perturbation until
+    /// value within bounds is returned. If argument is given,
+    /// this is the maximum number of retries to do and then
+    /// fall back to trimming. Zero means retry indefinitely.
+    Retry(usize)
+}
+
+pub struct BoundedPerturbation<const LEN: usize, T: PerturbationOperator<Chromosome = SVector<f64, LEN>>> {
+    min: SVector<f64, LEN>,
+    max: SVector<f64, LEN>,
+    min_max: SVector<(f64, f64), LEN>,
+    strategy: BoundedPerturbationStrategy,
+    perturbation: T,
+}
+
+impl<const LEN: usize, T: PerturbationOperator<Chromosome = SVector<f64, LEN>>> BoundedPerturbation<LEN, T> {
+    pub fn new(
+        perturbation: T,
+        min: SVector<f64, LEN>,
+        max: SVector<f64, LEN>,
+        strategy: BoundedPerturbationStrategy
+    ) -> Self {
+        let min_max = min.zip_map(&max, |min, max| (min, max));
+        Self {
+            min,
+            max,
+            min_max,
+            strategy,
+            perturbation
+        }
+    }
+
+    fn within_bounds(&self, chromosome: &SVector<f64, LEN>) -> bool {
+        chromosome.iter()
+            .zip(self.min_max.iter())
+            .all(|(&c, &(min, max))| c <= max && c >= min)
+    }
+
+    fn bound(&self, mut chromosome: SVector<f64, LEN>) -> SVector<f64, LEN> {
+        chromosome
+            .zip_apply(&self.min_max, |c, (min, max)| *c = c.clamp(min, max));
+
+        chromosome
+    }
+
+    fn retry_perturb(self: &mut Self, chromosome: &SVector<f64, LEN>, retries: Option<usize>) -> SVector<f64, LEN> {
+        let perturbed = self.perturbation.perturb(chromosome);
+
+        if self.within_bounds(&perturbed) {
+            return perturbed;
+        }
+
+        match retries {
+            Some(0) | None => self.bound(perturbed),
+            Some(retries) => self.retry_perturb(chromosome, Some(retries - 1))
+        }
+    }
+}
+
+impl<const LEN: usize, T> PerturbationOperator for BoundedPerturbation<LEN, T>
+where
+    T: PerturbationOperator<Chromosome = SVector<f64, LEN>>
+{
+    type Chromosome = SVector<f64, LEN>;
+
+    fn perturb(self: &mut Self, chromosome: &Self::Chromosome) -> Self::Chromosome {
+        match self.strategy {
+            BoundedPerturbationStrategy::Trim => self.retry_perturb(chromosome, None),
+            BoundedPerturbationStrategy::Retry(retries) => self.retry_perturb(chromosome, Some(retries))
+        }
+    }
+}
+
 #[cfg(test)]
 pub mod tests {
     use crate::binary_string::BinaryString;