Bugfix: incorrect use of constexpr qualifier

src/pythia6m/interface/event.hh

@@ -24,7 +24,7 @@ struct particle {
   double mass;
 
   particle() = default;
-  
+
   // create a particle from using the global pythia particle index
   particle(const int32_t idx);
 
@@ -61,19 +61,15 @@ struct event {
   event& operator=(const event&) = default;
   event& operator=(event&& rhs);
 
-  constexpr const particle& beam() const {
-    return particles[0];
-  }
-  constexpr const particle& target() const {
-    return particles[1];
-  }
+  const particle& beam() const { return particles[0]; }
+  const particle& target() const { return particles[1]; }
 
   // print a LUND event record for all final state particles
   void print(std::ostream& os,
              std::function<bool(const particle&)> selector) const;
 };
 
-// e+p leptoproduction 
+// e+p leptoproduction
 struct ep_event : event {
   ROOT::Math::XYZTVector q;
   double Q2;
@@ -105,7 +101,6 @@ struct photo_event : event {
   }
 };
 
-
-} // ns pythia6m
+} // namespace pythia6m
 
 #endif