Merge pull request #2436 from stan-dev/bugfix/issue-2435

Fix 2435

Author: bbbales2

stan/math/prim/fun/stan_print.hpp

@@ -16,30 +16,34 @@ void stan_print(std::ostream* o, const T& x) {
 
 template <typename EigVec, require_eigen_vector_t<EigVec>* = nullptr>
 void stan_print(std::ostream* o, const EigVec& x) {
+  const auto& x_ref = to_ref(x);
+
   *o << '[';
-  for (int i = 0; i < x.size(); ++i) {
+  for (int i = 0; i < x_ref.size(); ++i) {
     if (i > 0) {
       *o << ',';
     }
-    stan_print(o, x(i));
+    stan_print(o, x_ref.coeff(i));
   }
   *o << ']';
 }
 
 template <typename EigMat, require_eigen_t<EigMat>* = nullptr,
           require_not_eigen_vector_t<EigMat>* = nullptr>
 void stan_print(std::ostream* o, const EigMat& x) {
+  const auto& x_ref = to_ref(x);
+
   *o << '[';
-  for (int i = 0; i < x.rows(); ++i) {
+  for (int i = 0; i < x_ref.rows(); ++i) {
     if (i > 0) {
       *o << ',';
     }
     *o << '[';
-    for (int j = 0; j < x.cols(); ++j) {
+    for (int j = 0; j < x_ref.cols(); ++j) {
       if (j > 0) {
         *o << ',';
       }
-      stan_print(o, x.coeff(i, j));
+      stan_print(o, x_ref.coeff(i, j));
     }
     *o << ']';
   }

test/unit/math/prim/fun/stan_print_test.cpp

@@ -0,0 +1,71 @@
+#include <stan/math/prim.hpp>
+#include <gtest/gtest.h>
+
+TEST(MathPrim, basic_print) {
+  int i = 1;
+  double d = 1.0;
+  Eigen::VectorXd v = Eigen::VectorXd::Ones(1);
+  Eigen::RowVectorXd rv = Eigen::RowVectorXd::Ones(1);
+  Eigen::MatrixXd m = Eigen::MatrixXd::Ones(1, 1);
+  std::vector<double> a(1, 1);
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, i);
+    EXPECT_TRUE(s.str().find("1") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, d);
+    EXPECT_TRUE(s.str().find("1") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, v);
+    EXPECT_TRUE(s.str().find("[1]") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, rv);
+    EXPECT_TRUE(s.str().find("[1]") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, m);
+    EXPECT_TRUE(s.str().find("[[1]]") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, a);
+    EXPECT_TRUE(s.str().find("[1]") != std::string::npos);
+  }
+}
+
+TEST(MathPrim, basic_expressions) {
+  Eigen::VectorXd v = Eigen::VectorXd::Ones(2);
+  Eigen::RowVectorXd rv = Eigen::RowVectorXd::Ones(2);
+  Eigen::MatrixXd m = Eigen::MatrixXd::Ones(2, 2);
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, v * v.transpose());
+    EXPECT_TRUE(s.str().find("[[1,1],[1,1]]") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, rv * m);
+    EXPECT_TRUE(s.str().find("[2,2]") != std::string::npos);
+  }
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, m * m);
+    EXPECT_TRUE(s.str().find("[[2,2],[2,2]]") != std::string::npos);
+  }
+}

test/unit/math/rev/fun/stan_print_test.cpp

@@ -0,0 +1,16 @@
+#include <stan/math/rev.hpp>
+#include <test/unit/math/rev/fun/util.hpp>
+#include <test/unit/util.hpp>
+#include <gtest/gtest.h>
+
+TEST(AgradRev, stan_print) {
+  using stan::math::var;
+
+  var a = 5.0;
+
+  {
+    std::stringstream s;
+    stan::math::stan_print(&s, a);
+    EXPECT_TRUE(s.str().find("5") != std::string::npos);
+  }
+}