Add ValueAlias for ValueType reconstruction

src/type_traits/complex_help.hpp

@@ -12,6 +12,9 @@
 #ifndef QMCPLUSPLUS_COMPLEX_HELP_HPP
 #define QMCPLUSPLUS_COMPLEX_HELP_HPP
 
+#include <type_traits>
+#include <complex>
+
 namespace qmcplusplus
 {
 template<typename T>
@@ -26,24 +29,54 @@ using IsComplex = std::enable_if_t<IsComplex_t<T>::value, bool>;
 template<typename T>
 using IsReal = std::enable_if_t<std::is_floating_point<T>::value, bool>;
 
-template <typename T, typename = bool>
-struct RealAlias_impl {};
+template<typename T, typename = bool>
+struct RealAlias_impl
+{};
 
-template <typename T>
-struct RealAlias_impl<T, IsReal<T>> { using value_type = T; };
+template<typename T>
+struct RealAlias_impl<T, IsReal<T>>
+{
+  using value_type = T;
+};
 
-template <typename T>
-struct RealAlias_impl<T, IsComplex<T>> { using value_type = typename T::value_type; };
+template<typename T>
+struct RealAlias_impl<T, IsComplex<T>>
+{
+  using value_type = typename T::value_type;
+};
 
 /** If you have a function templated on a value that can be real or complex
  *   and you need to get the base Real type if its complex or just the real.
  *
  *  If you try to do this on anything but a fp or a std::complex<fp> you will
  *  get a compilation error.
  */
-template <typename T>
+template<typename T>
 using RealAlias = typename RealAlias_impl<T>::value_type;
 
+template<typename TREAL, typename TREF, typename = bool>
+struct ValueAlias_impl
+{};
+
+template<typename TREAL, typename TREF>
+struct ValueAlias_impl<TREAL, TREF, IsReal<TREF>>
+{
+  using value_type = TREAL;
+};
+
+template<typename TREAL, typename TREF>
+struct ValueAlias_impl<TREAL, TREF, IsComplex<TREF>>
+{
+  using value_type = std::complex<TREAL>;
+};
+
+/** If you need to make a value type of a given precision based on a reference value type
+ *  set the desired POD float point type as TREAL and set the reference type as TREF.
+ *  If TREF is real/complex, the generated Value type is real/complex.
+ */
+template<typename TREAL, typename TREF, typename = std::enable_if_t<std::is_floating_point<TREAL>::value>>
+using ValueAlias = typename ValueAlias_impl<TREAL, TREF>::value_type;
+
 ///real part of a scalar. Cannot be replaced by std::real due to AFQMC specific needs.
 inline float real(const float& c) { return c; }
 inline double real(const double& c) { return c; }
@@ -59,7 +92,7 @@ inline float conj(const float& c) { return c; }
 inline double conj(const double& c) { return c; }
 inline std::complex<float> conj(const std::complex<float>& c) { return std::conj(c); }
 inline std::complex<double> conj(const std::complex<double>& c) { return std::conj(c); }
-  
+
 } // namespace qmcplusplus
 
 #endif

src/type_traits/tests/CMakeLists.txt

@@ -14,7 +14,7 @@ set(SRC_DIR type_traits)
 set(UTEST_EXE test_${SRC_DIR})
 set(UTEST_NAME deterministic-unit_test_${SRC_DIR})
 
-set(TEST_SRCS test_qmctypes.cpp test_template_types.cpp)
+set(TEST_SRCS test_qmctypes.cpp test_template_types.cpp test_complex_helper.cpp)
 add_executable(${UTEST_EXE} ${TEST_SRCS})
 target_link_libraries(${UTEST_EXE} catch_main containers)
 

src/type_traits/tests/test_complex_helper.cpp

@@ -0,0 +1,46 @@
+//////////////////////////////////////////////////////////////////////////////////////
+// This file is distributed under the University of Illinois/NCSA Open Source License.
+// See LICENSE file in top directory for details.
+//
+// Copyright (c) 2023 QMCPACK developers
+//
+// File developed by: Ye Luo, [email protected], Argonne National Laboratory
+//
+// File created by: Ye Luo, [email protected], Argonne National Laboratory
+//////////////////////////////////////////////////////////////////////////////////////
+
+#include "catch.hpp"
+#include "type_traits/complex_help.hpp"
+
+namespace qmcplusplus
+{
+template<typename P>
+class TestComplexHelper
+{
+  using Cmplx        = std::complex<P>;
+  using Real         = RealAlias<Cmplx>;
+  using CmplxRebuild = ValueAlias<P, Cmplx>;
+  using RealRebuild  = ValueAlias<P, Real>;
+
+public:
+  void run()
+  {
+    Cmplx aa;
+    CmplxRebuild bb;
+    aa = bb;
+
+    Real cc;
+    RealRebuild dd(0);
+    cc = dd;
+  }
+};
+
+TEST_CASE("complex_helper", "[type_traits]")
+{
+  TestComplexHelper<float> float_test;
+  float_test.run();
+  TestComplexHelper<double> double_test;
+  double_test.run();
+}
+
+} // namespace qmcplusplus