Some tweaks to the subset class (allow const/ref, add operator SEXP

Author: kevinushey

inst/include/Rcpp/vector/Subsetter.h

@@ -103,23 +103,12 @@ class SubsetProxy {
         return *this;
     }
 
-    template <int OtherRTYPE, template <class> class OtherStoragePolicy>
-    operator Vector<OtherRTYPE, OtherStoragePolicy>() const {
-        int n = indices.size();
-        Vector<OtherRTYPE, OtherStoragePolicy> output = no_init(n);
-        for (int i=0; i < n; ++i) {
-            output[i] = lhs[ indices[i] ];
-        }
-        SEXP names = Rf_getAttrib(lhs, R_NamesSymbol);
-        if (!Rf_isNull(names)) {
-            Shield<SEXP> out_names( Rf_allocVector(STRSXP, n) );
-            for (int i=0; i < n; ++i) {
-                SET_STRING_ELT(out_names, i, STRING_ELT(names, indices[i]));
-            }
-            Rf_setAttrib(output, R_NamesSymbol, out_names);
-        }
-        Rf_copyMostAttrib(lhs, output);
-        return output;
+    operator Vector<RTYPE, StoragePolicy>() const {
+        return get_vec();
+    }
+    
+    operator SEXP() const {
+        return wrap( get_vec() );
     }
 
 private:
@@ -184,6 +173,24 @@ class SubsetProxy {
             }
         }
     }
+    
+    Vector<RTYPE, StoragePolicy> get_vec() const {
+        int n = indices.size();
+        Vector<RTYPE, StoragePolicy> output = no_init(n);
+        for (int i=0; i < n; ++i) {
+            output[i] = lhs[ indices[i] ];
+        }
+        SEXP names = Rf_getAttrib(lhs, R_NamesSymbol);
+        if (!Rf_isNull(names)) {
+            Shield<SEXP> out_names( Rf_allocVector(STRSXP, n) );
+            for (int i=0; i < n; ++i) {
+                SET_STRING_ELT(out_names, i, STRING_ELT(names, indices[i]));
+            }
+            Rf_setAttrib(output, R_NamesSymbol, out_names);
+        }
+        Rf_copyMostAttrib(lhs, output);
+        return output;
+    }
 
     LHS_t& lhs;
     const RHS_t& rhs;

inst/include/Rcpp/vector/Vector.h

@@ -325,6 +325,15 @@ class Vector :
         );
     }
 
+    template <int RHS_RTYPE, bool RHS_NA, typename RHS_T>
+    const SubsetProxy<RTYPE, StoragePolicy, RHS_RTYPE, RHS_NA, RHS_T>
+    operator[](const VectorBase<RHS_RTYPE, RHS_NA, RHS_T>& rhs) const {
+        return SubsetProxy<RTYPE, StoragePolicy, RHS_RTYPE, RHS_NA, RHS_T>(
+            const_cast< Vector<RTYPE, StoragePolicy>& >(*this),
+            rhs
+        );
+    }
+    
     Vector& sort(){
         typename traits::storage_type<RTYPE>::type* start = internal::r_vector_start<RTYPE>( Storage::get__() ) ;
         std::sort( 

inst/unitTests/cpp/Subset.cpp

@@ -51,3 +51,8 @@ NumericVector subset_test_assign(NumericVector x) {
     x[ x > 0 ] = 0;
     return x;
 }
+
+// [[Rcpp::export]]
+NumericVector subset_test_constref(NumericVector const& x, IntegerVector const& y) {
+    return x[y];
+}