From ffb4080f1498fb132cd74e5df5a728e065e503b1 Mon Sep 17 00:00:00 2001
From: "p.vanderwilt" <p.van.der.wilt@brabantsedelta.nl>
Date: Thu, 6 Nov 2025 17:24:10 +0100
Subject: [PATCH] Refactor boundary condition handling in Reactor_PFR class for
 improved clarity and efficiency

---
 src/specificClass.js | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/specificClass.js b/src/specificClass.js
index 228d077..12ba0da 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -365,11 +365,10 @@ class Reactor_PFR extends Reactor {
    *  for outlet, apply regular Danckwerts BC (Neumann BC with no flux)
    */
   _applyBoundaryConditions() {
+    // Upstream BC
     if (this.upstreamReactor) {
       // Open boundary
-      for (let i = 0; i < BC_PADDING; i++) {
-        this.extendedState[i] = this.upstreamReactor.state.at(i-BC_PADDING);
-      }
+      this.extendedState.splice(0, BC_PADDING, ...this.upstreamReactor.state.slice(-BC_PADDING)); 
     } else {
       if (math.sum(this.Fs) > 0) {
         // Danckwerts BC
@@ -383,11 +382,10 @@ class Reactor_PFR extends Reactor {
       }
     }
 
+    // Downstream BC
     if (this.downstreamReactor) {
       // Open boundary
-      for (let i = 0; i < BC_PADDING; i++) {
-        this.extendedState[this.n_x+BC_PADDING+i] = this.downstreamReactor.state[i];
-      }
+      this.extendedState.splice(this.n_x+BC_PADDING, BC_PADDING, ...this.downstreamReactor.state.slice(0, BC_PADDING));
     } else {
       // Neumann BC (no flux)
       this.extendedState.fill(this.extendedState.at(-1-BC_PADDING), BC_PADDING+this.n_x);