Added as() and clone() to Nullable

inst/include/Rcpp/Nullable.h

@@ -91,6 +91,13 @@ namespace Rcpp {
             return m_sexp;
         }
 
+        /**
+         * Boolean test for usability as a T
+         */
+        inline bool isUsable() const {
+            return m_set && !Rf_isNull(m_sexp);
+        }
+
         /**
          * Boolean test for NULL
          *
@@ -116,6 +123,16 @@ namespace Rcpp {
          */
         inline bool isSet(void) const { return m_set; }
 
+        /**
+         * Returns m_sexp as a T
+         */
+        inline T as() { return get(); }
+
+        /**
+         * Return a clone of m_sexp as a T
+         */
+        inline T clone() const { return Rcpp::clone(get()); }
+
     private:
         SEXP m_sexp;
         bool m_set;

inst/unitTests/cpp/misc.cpp

@@ -198,3 +198,21 @@ SEXP testNullableGet(const Nullable<NumericMatrix>& M) {
     return M.get();
 }
 
+// [[Rcpp::export]]
+NumericMatrix testNullableAs(Nullable<NumericMatrix>& M) {
+    return M.as();
+}
+
+// [[Rcpp::export]]
+NumericMatrix testNullableClone(const Nullable<NumericMatrix>& M) {
+    return M.clone();
+}
+
+// [[Rcpp::export]]
+SEXP testNullableIsUsable(const Nullable<NumericMatrix>& M) {
+    if (M.isUsable()) {
+        return M.clone();
+    } else {
+        return R_NilValue;
+    }
+}

inst/unitTests/runit.misc.R

@@ -185,4 +185,23 @@ if (.runThisTest) {
         M <- matrix(1:4, 2, 2)
         checkEquals( testNullableGet(M), M )
     }
+
+    test.NullableAccessAs <- function() {
+        M <- matrix(1:4, 2, 2)
+        checkEquals( testNullableAs(M), M )
+    }
+
+    test.NullableAccessClone <- function() {
+        M <- matrix(1:4, 2, 2)
+        checkEquals( testNullableClone(M), M )
+    }
+
+    test.NullableIsUsableTrue <- function() {
+	M <- matrix(1:4, 2, 2)
+        checkEquals( testNullableIsUsable(M), M)
+    }
+
+    test.NullableIsUsableFalse <- function() {
+        checkTrue(is.null(testNullableIsUsable(NULL)))
+    }
 }