mcc_pcm.h: add mccDefaultPCMTypeString free function

mcc_pcm_fit.h: computeModel now accepts PCM data type of MccDefaultPCM-
class descendants

include/mcc/mcc_pcm.h

@@ -120,6 +120,17 @@ static constexpr std::string_view MccDefaultPCMTypeString =
 #endif
                                                            : "UNKNOWN";
 
+
+static constexpr std::string_view mccDefaultPCMTypeString(MccDefaultPCMType type)
+{
+    return type == MccDefaultPCMType::PCM_TYPE_GEOMETRY ? "GEOMETRY"
+#ifdef USE_BSPLINE_PCM
+           : type == MccDefaultPCMType::PCM_TYPE_GEOMETRY_BSPLINE ? "GEOMETRY-BSPLINE"
+           : type == MccDefaultPCMType::PCM_TYPE_GEOMETRY_BSPLINE ? "BSPLINE"
+#endif
+                                                                  : "UNKNOWN";
+}
+
 template <MccMountType MOUNT_TYPE>
 class MccDefaultPCM : public mcc_pcm_interface_t<std::error_code>
 {
@@ -176,6 +187,8 @@ public:
 #endif
 
     struct pcm_data_t {
+        typedef MccDefaultPCM pcm_t;
+
         MccDefaultPCMType type{MccDefaultPCMType::PCM_TYPE_GEOMETRY};
         double siteLatitude{0.0};  // in radians
 

include/mcc/mcc_pcm_fit.h

@@ -279,8 +279,9 @@ public:
     //
     // WARNING: the input knots for inverse B-spline are ignored so the direct and inverse B-spline coefficients are
     //          calculated on the same mesh!
-    compute_result_t computeModel(MccDefaultPCM<MOUNT_TYPE>::pcm_data_t& pcm_data,
-                                  compute_params_t const& comp_params = {})
+    template <typename PCM_DATA_T>
+    compute_result_t computeModel(PCM_DATA_T& pcm_data, compute_params_t const& comp_params = {})
+        requires(std::derived_from<typename PCM_DATA_T::pcm_t, MccDefaultPCM<MOUNT_TYPE>>)
     {
         compute_result_t result{.pcm_type = pcm_data.type, .error = MccPCMFitterErrorCode::ERROR_OK};