alternate strategy

Author: kevinushey

ChangeLog

@@ -1,3 +1,9 @@
+2014-09-14  Kevin Ushey  <kevinushey@gmail.com>
+
+        * inst/include/Rcpp/vector/Vector.h: Alternate strategy using SFINAE
+        * inst/include/Rcpp/traits/traits.h: Idem
+        * inst/include/Rcpp/traits/enable_if.h: Idem
+
 2014-09-13  Kevin Ushey  <kevinushey@gmail.com>
 
         * inst/include/Rcpp/vector/Vector.h: Allow logical vectors to be created

inst/include/Rcpp/traits/enable_if.h

@@ -0,0 +1,18 @@
+#ifndef RCPP_TRAITS_ENABLE_IF_H
+#define RCPP_TRAITS_ENABLE_IF_H
+
+namespace Rcpp {
+namespace traits {
+
+template <bool B, typename T = void>
+struct enable_if {};
+
+template <typename T>
+struct enable_if<true, T> {
+    typedef T type;
+};
+
+}
+}
+
+#endif

inst/include/Rcpp/traits/traits.h

@@ -37,6 +37,7 @@ struct int2type { enum { value = I }; };
 
 #include <Rcpp/traits/integral_constant.h>
 #include <Rcpp/traits/same_type.h>
+#include <Rcpp/traits/enable_if.h>
 #include <Rcpp/traits/is_wide_string.h>
 #include <Rcpp/traits/char_type.h>
 #include <Rcpp/traits/named_object.h>

inst/include/Rcpp/vector/Vector.h

@@ -89,13 +89,13 @@ class Vector :
         fill( u ) ;
     }
 
-    // constructor for CharacterVector() 
+    // constructor for CharacterVector()
     Vector( const std::string& st ){
         RCPP_DEBUG_2( "Vector<%d>( const std::string& = %s )", RTYPE, st.c_str() )
         Storage::set__( internal::vector_from_string<RTYPE>(st) ) ;
     }
 
-    // constructor for CharacterVector() 
+    // constructor for CharacterVector()
     Vector( const char* st ) {
         RCPP_DEBUG_2( "Vector<%d>( const char* = %s )", RTYPE, st )
         Storage::set__(internal::vector_from_string<RTYPE>(st) ) ;
@@ -119,8 +119,9 @@ class Vector :
         }
     }
 
-    template <typename T = typename Rcpp::traits::if_<RTYPE == LGLSXP, bool, void>::type>
-    Vector(bool value) {
+    // Enable construction from bool for LogicalVectors
+    template <int T = RTYPE>
+    Vector(bool value, typename Rcpp::traits::enable_if<T == LGLSXP, void>::type* = 0) {
         Storage::set__(Rf_allocVector(RTYPE, 1));
         fill(value);
     }