add support for Eigen::Transform

include/glaze/ext/eigen.hpp

@@ -195,6 +195,33 @@ namespace glz
             GLZ_MATCH_CLOSE_BRACKET;
          }
       };
+
+      template <typename Scalar, int Dim, int Mode>
+      struct from<JSON, Eigen::Transform<Scalar, Dim, Mode>>
+      {
+         template <auto Opts>
+         static void op(auto& value, is_context auto&& ctx, auto&& it, auto&& end)
+         {
+            constexpr auto size =
+               Mode == Eigen::TransformTraits::AffineCompact ? (Dim + 1) * Dim : (Dim + 1) * (Dim + 1);
+            std::span<Scalar, size> view(value.data(), size);
+            detail::read<JSON>::op<Opts>(view, ctx, it, end);
+         }
+      };
+
+      template <typename Scalar, int Dim, int Mode>
+      struct to<JSON, Eigen::Transform<Scalar, Dim, Mode>>
+      {
+         template <auto Opts>
+         static void op(auto&& value, is_context auto&& ctx, auto&& b, auto&& ix)
+         {
+            constexpr auto size =
+               Mode == Eigen::TransformTraits::AffineCompact ? (Dim + 1) * Dim : (Dim + 1) * (Dim + 1);
+            std::span<Scalar, size> view(value.data(), size);
+            using Value = std::remove_cvref_t<decltype(value)>;
+            detail::to<JSON, Value>::template op<Opts>(view, ctx, b, ix);
+         }
+      };
    } // namespace detail
 } // namespace glaze
 

tests/eigen_test/eigen_test.cpp

@@ -4,6 +4,7 @@
 #include "glaze/ext/eigen.hpp"
 
 #include <Eigen/Core>
+#include <Eigen/Geometry>
 #include <any>
 #include <chrono>
 #include <iostream>
@@ -394,4 +395,21 @@ int main()
       expect(!glz::read_json(e, b));
       expect(bool(m == e));
    };
+
+   "Eigen::Transform"_test = [] {
+      Eigen::Isometry3d pose1, pose2;
+      pose1.setIdentity();
+      pose1.translation() << 1.111, 2.222, 3.333;
+      std::string buffer = glz::write_json(pose1).value();
+      expect(buffer == "[1,0,0,0,0,1,0,0,0,0,1,0,1.111,2.222,3.333,1]");
+      expect(not glz::read_json(pose2, buffer));
+      expect(pose1.matrix() == pose2.matrix());
+
+      Eigen::AffineCompact2d c1, c2;
+      c1.setIdentity();
+      buffer = glz::write_json(c1).value();
+      expect(buffer == "[1,0,0,1,0,0]");
+      expect(not glz::read_json(c2, buffer));
+      expect(c1.matrix() == c2.matrix());
+   };
 }