From 81bf0a67daf332d51b1479a60bcc8077388300f2 Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Thu, 18 Jul 2019 13:15:26 -0500
Subject: [PATCH] Implementing intersection and union operators for
 BoundingBox.

---
 include/openmc/surface.h | 34 +++++++++++++++++++++++-----------
 src/cell.cpp             | 12 ++++++------
 src/surface.cpp          |  3 +--
 3 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/include/openmc/surface.h b/include/openmc/surface.h
index 10b4a4c27..a7d107ee3 100644
--- a/include/openmc/surface.h
+++ b/include/openmc/surface.h
@@ -50,26 +50,38 @@ struct BoundingBox
   double zmin = -INFTY;
   double zmax = INFTY;
 
-  // in-place update to include another bounding box
-  inline void update(const BoundingBox& other) {
-    xmin = std::min(xmin, other.xmin);
-    xmax = std::max(xmax, other.xmax);
-    ymin = std::min(ymin, other.ymin);
-    ymax = std::max(ymax, other.ymax);
-    zmin = std::min(zmin, other.zmin);
-    zmax = std::max(zmax, other.zmax);
-  };
 
-  // in-place intersection with another bounding box
-  inline void intersect(const BoundingBox& other) {
+  inline BoundingBox operator &(const BoundingBox& other) {
+    BoundingBox result = *this;
+    return result &= other;
+  }
+
+  inline BoundingBox operator |(const BoundingBox& other) {
+    BoundingBox result = *this;
+    return result |= other;
+  }
+
+  // intersect operator
+  inline BoundingBox& operator &=(const BoundingBox& other) {
     xmin = std::max(xmin, other.xmin);
     xmax = std::min(xmax, other.xmax);
     ymin = std::max(ymin, other.ymin);
     ymax = std::min(ymax, other.ymax);
     zmin = std::max(zmin, other.zmin);
     zmax = std::min(zmax, other.zmax);
+    return *this;
   }
 
+  // union operator
+  inline BoundingBox& operator |=(const BoundingBox& other) {
+    xmin = std::min(xmin, other.xmin);
+    xmax = std::max(xmax, other.xmax);
+    ymin = std::min(ymin, other.ymin);
+    ymax = std::max(ymax, other.ymax);
+    zmin = std::min(zmin, other.zmin);
+    zmax = std::max(zmax, other.zmax);
+    return *this;
+  }
 
 };
 
diff --git a/src/cell.cpp b/src/cell.cpp
index 1dff5caf9..fc9a25e2e 100644
--- a/src/cell.cpp
+++ b/src/cell.cpp
@@ -213,7 +213,7 @@ BoundingBox Universe::bounding_box() const {
   } else {
     for (const auto& cell : cells_) {
       auto& c = model::cells[cell];
-      bbox.update(c->bounding_box());
+      bbox |= c->bounding_box();
     }
   }
   return bbox;
@@ -581,7 +581,7 @@ CSGCell::to_hdf5(hid_t cell_group) const
 BoundingBox CSGCell::bounding_box_simple() const {
   BoundingBox bbox;
   for (int32_t token : rpn_) {
-    bbox.intersect(model::surfaces[abs(token)-1]->bounding_box(token > 0));
+    bbox &= model::surfaces[abs(token)-1]->bounding_box(token > 0);
   }
   return bbox;
 }
@@ -603,9 +603,9 @@ BoundingBox CSGCell::bounding_box_complex(std::vector<int32_t> rpn) const {
 
     if (two >= OP_UNION) {
       if (two == OP_UNION) {
-        current.update(model::surfaces[abs(one)-1]->bounding_box(one > 0));
+        current |= model::surfaces[abs(one)-1]->bounding_box(one > 0);
       } else if (two == OP_INTERSECTION) {
-        current.intersect(model::surfaces[abs(one)-1]->bounding_box(one > 0));
+        current &= model::surfaces[abs(one)-1]->bounding_box(one > 0);
       }
     } else {
     // two surfaces in a row, create sub-rpn for region in parenthesis
@@ -638,9 +638,9 @@ BoundingBox CSGCell::bounding_box_complex(std::vector<int32_t> rpn) const {
       BoundingBox sub_box = bounding_box_complex(subrpn);
       // combine the sub-rpn bounding box with our current cell box
       if (op == OP_UNION) {
-        current.update(sub_box);
+        current |= sub_box;
       } else if (op == OP_INTERSECTION) {
-        current.intersect(sub_box);
+        current &= sub_box;
       }
     }
   }
diff --git a/src/surface.cpp b/src/surface.cpp
index 45cd025ba..14d077cff 100644
--- a/src/surface.cpp
+++ b/src/surface.cpp
@@ -1191,8 +1191,7 @@ void read_surfaces(pugi::xml_node node)
       }
 
       // See if this surface makes part of the global bounding box.
-      BoundingBox bb = surf->bounding_box(true);
-      bb.intersect(surf->bounding_box(false));
+      auto bb = surf->bounding_box(true) & surf->bounding_box(false);
       if (bb.xmin > -INFTY && bb.xmin < xmin) {
         xmin = bb.xmin;
         i_xmin = i_surf;