make sure operations between scalar and matrix don't change rhs

Author: thirdwing

inst/include/Rcpp/vector/Matrix.h

@@ -269,8 +269,7 @@ RCPP_GENERATE_MATRIX_SCALAR_OPERATOR(/)
     inline typename traits::enable_if< traits::is_convertible< typename traits::remove_const_and_reference< T >::type,        \
          typename Matrix<RTYPE, StoragePolicy>::stored_type >::value, Matrix<RTYPE, StoragePolicy> >::type                    \
              operator __OPERATOR__ (const T &lhs, const Matrix<RTYPE, StoragePolicy> &rhs) {                                  \
-        Vector<RTYPE, StoragePolicy> v = static_cast<const Vector<RTYPE, StoragePolicy> &>(rhs);                              \
-        v = lhs __OPERATOR__ v;                                                                                               \
+        Vector<RTYPE, StoragePolicy> v = lhs __OPERATOR__ static_cast<const Vector<RTYPE, StoragePolicy> &>(rhs);             \
         v.attr("dim") = Vector<INTSXP>::create(rhs.nrow(), rhs.ncol());                                                       \
         return as< Matrix<RTYPE, StoragePolicy> >(v);                                                                         \
     }

inst/tinytest/cpp/Matrix.cpp

@@ -337,6 +337,20 @@ NumericMatrix matrix_scalar_plus2(const NumericMatrix & x, double y) {
     return y + x;
 }
 
+// [[Rcpp::export]]
+NumericMatrix matrix_scalar_plus3(const NumericMatrix & x, double y) {
+    NumericMatrix z(x.rows(), x.cols());
+    z = x + y;
+    return x;
+}
+
+// [[Rcpp::export]]
+NumericMatrix matrix_scalar_plus4(const NumericMatrix & x, double y) {
+    NumericMatrix z(x.rows(), x.cols());
+    z = y + x;
+    return x;
+}
+
 // [[Rcpp::export]]
 NumericMatrix matrix_scalar_divide(const NumericMatrix & x, double y) {
     return x / y;
@@ -347,6 +361,20 @@ NumericMatrix matrix_scalar_divide2(const NumericMatrix & x, double y) {
     return y / x;
 }
 
+// [[Rcpp::export]]
+NumericMatrix matrix_scalar_divide3(const NumericMatrix & x, double y) {
+    NumericMatrix z(x.rows(), x.cols());
+    z = x / y;
+    return x;
+}
+
+// [[Rcpp::export]]
+NumericMatrix matrix_scalar_divide4(const NumericMatrix & x, double y) {
+    NumericMatrix z(x.rows(), x.cols());
+    z = y / x;
+    return x;
+}
+
 // 24 October 2016
 // eye, ones, and zeros static member functions
 

inst/tinytest/test_matrix.R

@@ -213,8 +213,13 @@ expect_equal(transposeCharacter(M), t(M), info="character transpose with row and
 M <- matrix(c(1:12), 3, 4)
 expect_equal(matrix_scalar_plus(M, 2), M + 2, info="matrix + scalar")
 expect_equal(matrix_scalar_plus2(M, 2), 2 + M, info="scalar + matrix")
+expect_equal(matrix_scalar_plus3(M, 2), M, info="matrix + scalar should not change input matrix")
+expect_equal(matrix_scalar_plus4(M, 2), M, info="scalar + matrix should not change input matrix")
+
 expect_equal(matrix_scalar_divide(M, 2), M / 2, info="matrix / scalar")
 expect_equal(matrix_scalar_divide2(M, 2), 2 / M, info="scalar / matrix")
+expect_equal(matrix_scalar_divide3(M, 2), M, info="matrix / scalar should not change input matrix")
+expect_equal(matrix_scalar_divide4(M, 2), M, info="scalar / matrix should not change input matrix")
 
 ## 23 October 2016
 ## eye function