<fix>[PWMap::inverse]: fixed PWMap inverse singleton domain and constant expression

Author: Kalashnikovni

sbg/dom_ord_pwmap.cpp

@@ -440,8 +440,7 @@ DomOrdPWMap DomOrdPWMap::inverse() const
   DomOrdPWMap result;
 
   for (const MapEntry& entry : _pieces) {
-    Map m = entry.map();
-    result.emplace(Map{m.image(), m.law().inverse()});
+    result.emplace(entry.map().inverse());
   }
 
   return result;

sbg/map.cpp

@@ -128,6 +128,15 @@ Set Map::preImage(const Set& subcodom) const
     .intersection(_domain);
 }
 
+Map Map::inverse() const
+{
+  if (_domain.cardinal() == 1) {
+    return Map{image(), _domain.minElem()};
+  }
+
+  return Map{image(), _law.inverse()};
+}
+
 Map Map::composition(const Map& other) const
 {
   Set result_domain = _domain.intersection(other.image());

sbg/map.hpp

@@ -113,7 +113,13 @@ class Map {
    * @param subcodom Set of elements in the image of the map for which the
    * pre image will be calculated.
    */
-  Set preImage(const Set& subcodom) const; // opt
+  Set preImage(const Set& subcodom) const;
+
+  /**
+   * @brief Calculates the inverse of a map.
+   * Precondition: map should be bijective.
+   */
+  Map inverse() const;
 
   /**
    * @brief Calculate the composition of \p this with \p other, i.e.

sbg/ord_pwmap.cpp

@@ -416,8 +416,7 @@ OrdPWMap OrdPWMap::inverse() const
   OrdPWMap result;
 
   for (const MapEntry& entry : _pieces) {
-    Map m = entry.map();
-    result.emplace(Map{m.image(), m.law().inverse()});
+    result.emplace(entry.map().inverse());
   }
 
   return result;

sbg/unord_pwmap.cpp

@@ -248,7 +248,7 @@ UnordPWMap UnordPWMap::inverse() const
   UnordPWMap result;
 
   for (const Map& m : _pieces) {
-    result.emplaceBack(m.image(), m.law().inverse());
+    result.pushBack(m.inverse());
   }
 
   return result;