special casing for T and F. #217

NEWS.md

@@ -21,7 +21,9 @@ dplyr 0.1.0.99
 
 * `filter` handles scalar results (#217) and better handles scoping, e.g. 
   `filter(.,variable)` where `variable` is defined in the function that calls
-  `filter`
+  `filter`. It also handles `T` and `F` correctly as aliases to `TRUE` and 
+  `FALSE` only if there are no `T` or `F` variables in the data or 
+  in the scope. 
 
 * `select.grouped_df` fails when the grouping variables are not included
   in the selected variables (#170)

src/dplyr.cpp

@@ -874,6 +874,12 @@ SEXP assert_correct_filter_subcall(SEXP x, const SymbolSet& set, const Environme
             // look in the environment
             Shield<SEXP> res( Rf_findVar( x, env ) );
             if( res == R_UnboundValue ){
+                if( x == Rf_install("T") ){
+                    return Rf_ScalarLogical(TRUE) ;
+                } else if( x == Rf_install("F") ){
+                    return Rf_ScalarLogical(FALSE) ;    
+                }
+
                 std::stringstream s ;
                 s << "unknown column : " << CHAR(PRINTNAME(x)) ;
                 stop(s.str());