restored SelectProcess and added static_assert on input types

Framework/ProcessSequence/ProcessSequence.h

@@ -68,7 +68,10 @@ namespace corsika::process {
   public:
     template <class... Us>
     ProcessSequence(Us&&... us)
-        : storage_t(std::forward<Us>(us)...) {}
+        : storage_t(std::forward<Us>(us)...) {
+      static_assert((... && is_process_v<std::decay_t<Us>>),
+                    "all arguments must be processes");
+    }
 
     // example for a trait-based call:
     // void Hello() const  { detail::CallHello<T1,T2>::Call(A, B); }
@@ -229,43 +232,22 @@ namespace corsika::process {
     EProcessReturn SelectDecay(TParticle& vP, TSecondaries& vS,
                                corsika::units::si::InverseTimeType decay_select,
                                corsika::units::si::InverseTimeType& decay_inv_count) {
-      boost::ignore_unused(vP, vS, decay_select, decay_inv_count);
-
-      // if constexpr (t1ProcSeq) {
-      //   // if A is a process sequence --> check inside
-      //   const EProcessReturn ret = A.SelectDecay(vP, vS, decay_select,
-      //   decay_inv_count);
-      //   // if A did succeed, stop routine
-      //   if (ret != EProcessReturn::eOk) { return ret; }
-      // } else if constexpr (std::is_base_of_v<DecayProcess<T1type>, T1type>) {
-      //   // if this is not a ContinuousProcess --> evaluate probability
-      //   decay_inv_count += A.GetInverseLifetime(vP);
-      //   // check if we should execute THIS process and then EXIT
-      //   if (decay_select < decay_inv_count) { // more pedagogical: rndm_select <
-      //                                         // decay_inv_count / decay_inv_tot
-      //     A.DoDecay(vS);
-      //     return EProcessReturn::eDecayed;
-      //   }
-      // } // end branch A
-      //
-      // if constexpr (t2ProcSeq) {
-      //   // if A is a process sequence --> check inside
-      //   const EProcessReturn ret = B.SelectDecay(vP, vS, decay_select,
-      //   decay_inv_count);
-      //   // if A did succeed, stop routine
-      //   if (ret != EProcessReturn::eOk) { return ret; }
-      // } else if constexpr (std::is_base_of_v<DecayProcess<T2type>, T2type>) {
-      //   // if this is not a ContinuousProcess --> evaluate probability
-      //   decay_inv_count += B.GetInverseLifetime(vP);
-      //   // check if we should execute THIS process and then EXIT
-      //   if (decay_select < decay_inv_count) {
-      //     B.DoDecay(vS);
-      //     return EProcessReturn::eDecayed;
-      //   }
-      // } // end branch B
-      return EProcessReturn::eOk;
+      EProcessReturn ret = EProcessReturn::eOk;
+      apply<DecayProcess>([&](auto&& proc) {
+        if (ret == EProcessReturn::eOk) {
+          // if this is not a ContinuousProcess --> evaluate probability
+          decay_inv_count += proc.GetInverseLifetime(vP);
+          // check if we should execute THIS process and then EXIT
+          if (decay_select < decay_inv_count) {
+            proc.DoDecay(vS);
+            ret = EProcessReturn::eDecayed;
+          }
+        }
+      });
+      return ret;
     }
 
+    // TODO: this should be removed along with all Init() functions of the processes
     void Init() {
       boost::mp11::tuple_for_each(static_cast<storage_t&>(*this),
                                   [](auto&& proc) { proc.Init(); });