Merge pull request #215 from yixuan/sort_assert

Disable sorting for certain vector types

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,12 @@
+2014-12-11  Yixuan Qiu <[email protected]>
+
+        * inst/include/Rcpp/internal/r_vector.h: Internal functions to
+        help detect unqualified vector types for sorting, with the help
+        of Romain Francois
+        * inst/include/Rcpp/vector/Vector.h: Disallow sorting on List,
+        RawVector and ExpressionVector, from the discussion with
+        Dirk Eddelbuettel and Kevin Ushey
+
 2014-11-25  Dirk Eddelbuettel  <[email protected]>
 
         * inst/include/Rcpp/grow.h: Apply additional Shield<> use around tail

inst/include/Rcpp/internal/r_vector.h

@@ -84,6 +84,61 @@ inline void r_init_vector<EXPRSXP>(SEXP x){}
 template<>
 inline void r_init_vector<STRSXP>(SEXP x){}
 
+
+
+/**
+ * We do not allow List(RTYPE=VECSXP), RawVector(RTYPE=RAWSXP)
+ * or ExpressionVector(RTYPE=EXPRSXP) to be sorted, so it is
+ * desirable to issue a compiler error if user attempts to sort
+ * these types of Vectors.
+ *
+ * We declare a template class without defining the generic
+ * class body, but complete the definition in specialization
+ * of qualified Vector types. Hence when using this class
+ * on unqualified Vectors, the compiler will emit errors.
+ */
+template<int RTYPE>
+class Sort_is_not_allowed_for_this_type;
+
+/**
+ * Specialization for CPLXSXP, INTSXP, LGLSXP, REALSXP, and STRSXP
+ */
+template<>
+class Sort_is_not_allowed_for_this_type<CPLXSXP>
+{
+public:
+    static void do_nothing() {}
+};
+
+template<>
+class Sort_is_not_allowed_for_this_type<INTSXP>
+{
+public:
+    static void do_nothing() {}
+};
+
+template<>
+class Sort_is_not_allowed_for_this_type<LGLSXP>
+{
+public:
+    static void do_nothing() {}
+};
+
+template<>
+class Sort_is_not_allowed_for_this_type<REALSXP>
+{
+public:
+    static void do_nothing() {}
+};
+
+template<>
+class Sort_is_not_allowed_for_this_type<STRSXP>
+{
+public:
+    static void do_nothing() {}
+};
+
+
 } // internal
 } // Rcpp
 

inst/include/Rcpp/vector/Vector.h

@@ -349,6 +349,13 @@ class Vector :
     }
 
     Vector& sort(){
+        // sort() does not apply to List, RawVector or ExpressionVector.
+        //
+        // The function below does nothing for qualified Vector types,
+        // and is undefined for other types. Hence there will be a
+        // compiler error when sorting List, RawVector or ExpressionVector.
+        internal::Sort_is_not_allowed_for_this_type<RTYPE>::do_nothing();
+        
         typename traits::storage_type<RTYPE>::type* start = internal::r_vector_start<RTYPE>( Storage::get__() ) ;
         std::sort(
             start,