Correcting VLA issue, and add template specification for between Pose2 objects. More template specifcations will be needed on windows, unless another fix is found

gtsam/nonlinear/Expression.h

@@ -206,11 +206,20 @@ private:
     // with an execution trace, made up entirely of "Record" structs, see
     // the FunctionalNode class in expression-inl.h
     size_t size = traceSize();
+#ifdef _MSC_VER
+    ExecutionTraceStorage* traceStorage = new ExecutionTraceStorage[size];
+    ExecutionTrace<T> trace;
+    T value(traceExecution(values, trace, traceStorage));
+    trace.startReverseAD1(jacobians);
+    delete[] traceStorage;
+    return value;
+#else
     ExecutionTraceStorage traceStorage[size];
     ExecutionTrace<T> trace;
     T value(traceExecution(values, trace, traceStorage));
     trace.startReverseAD1(jacobians);
     return value;
+#endif
   }
 
   // be very selective on who can access these private methods:

gtsam_unstable/nonlinear/expressions.h

@@ -8,13 +8,26 @@
 #pragma once
 
 #include <gtsam/nonlinear/Expression.h>
+#include <gtsam/geometry/Pose2.h>
+#include <gtsam/geometry/Pose3.h>
 #include <boost/bind.hpp>
 
 namespace gtsam {
 
+// 2D Geometry
+  typedef Expression<Pose2> Pose2_;
+
+  Pose2_ between(const Pose2_& x, const Pose2_& p) {
+    Pose2(Pose2::*transform)(const Pose2& p,
+      boost::optional<Matrix3&> H1,
+      boost::optional<Matrix3&> H2) const = &Pose2::between;
+
+    return Pose2_(x, transform, p);
+  }
+
 // Generics
 
-template<class T>
+template<typename T>
 Expression<T> between(const Expression<T>& t1, const Expression<T>& t2) {
   return Expression<T>(t1, &T::between, t2);
 }