fix const correctness of Matrix::Column( const Matrix&, int)

Author: romainfrancois

inst/include/Rcpp/vector/MatrixColumn.h

@@ -44,7 +44,7 @@ class MatrixColumn : public VectorBase<RTYPE,true,MatrixColumn<RTYPE> > {
 
     MatrixColumn( const MATRIX& parent, int i ) :
         n(parent.nrow()),
-        start(parent.begin() + i * n ),
+        start( const_cast<MATRIX&>(parent).begin() + i * n ),
         const_start(parent.begin() + i *n)
     {
         if( i < 0 || i >= parent.ncol() ) throw index_out_of_bounds() ;

inst/unitTests/cpp/Matrix.cpp

@@ -225,3 +225,16 @@ NumericMatrix runit_no_init_matrix() {
     }
     return x;
 }
+
+void runit_const_Matrix_column_set( NumericMatrix::Column& col1, const NumericMatrix::Column& col2 ){
+    col1 = col2 ;    
+}
+
+// [[Rcpp::export]]
+NumericVector runit_const_Matrix_column( const NumericMatrix& m ){
+   NumericMatrix::Column col1( m, 0 ) ;
+   NumericMatrix::Column col2( m, 1 ) ;
+   runit_const_Matrix_column_set(col1, col2) ;
+   return col1 ;
+}
+

inst/unitTests/runit.Matrix.R

@@ -165,5 +165,10 @@ if (.runThisTest) {
       checkEquals(m, matrix(c(0, 1, 2, 3), nrow = 2))
     }
 
+    test.NumericMatrix.const.Column <- function(){
+      m <- matrix(as.numeric(1:9), nrow = 3)
+      res <- runit_const_Matrix_column(m)
+      checkEquals( m[,1], m[,2] )
+    }
 
 }