a simpler fix for constexpr_for in amrex (#1420)

interfaces/rhs_type.H

@@ -2,37 +2,13 @@
 #define rhs_type_H
 
 #include <AMReX_REAL.H>
+#include <AMReX_Loop.H>
 #include <network_properties.H>
 #ifdef SCREENING
 #include <screen.H>
 #endif
 #include <tfactors.H>
 
-// Implementation of "constexpr for" based on
-// https://artificial-mind.net/blog/2020/10/31/constexpr-for
-//
-// Approximates what one would get from a compile-time
-// unrolling of the loop
-// for (int i = 0; i < N; ++i) {
-//    f(i);
-// }
-//
-// The mechanism is recursive, we evaluate f(i) at the current
-// i and then call the for loop at i+1. f() is a lambda function
-// that provides the body of the loop and takes only an integer
-// i as its argument. It is assumed that at the loop call site
-// the lambda is declared [&] so that it can operate on whatever
-// data it needs.
-
-template<auto I, auto N, class F>
-AMREX_GPU_HOST_DEVICE AMREX_INLINE
-constexpr void constexpr_for (F&& f)
-{
-    if constexpr (I < N) {
-        f(std::integral_constant<decltype(I), I>());
-        constexpr_for<I+1, N>(f);
-    }
-}
 
 namespace RHS
 {

networks/rhs.H

@@ -4,6 +4,7 @@
 #include <AMReX.H>
 #include <AMReX_REAL.H>
 #include <AMReX_Print.H>
+#include <AMReX_Loop.H>
 
 #include <ArrayUtilities.H>
 #include <rhs_type.H>