From 5590cc29c32807ea50839dc28e07abe11bf8f428 Mon Sep 17 00:00:00 2001
From: Alexis Placet <2400067+Alex-PLACET@users.noreply.github.com>
Date: Wed, 29 Apr 2026 09:19:59 +0200
Subject: [PATCH 1/2] Enhance xmasked_view support for output streaming

---
 include/xtensor/io/xio.hpp | 14 ++++++++++++--
 test/test_xmasked_view.cpp | 17 +++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/xtensor/io/xio.hpp b/include/xtensor/io/xio.hpp
index fbc0cd3a0..2f31f9703 100644
--- a/include/xtensor/io/xio.hpp
+++ b/include/xtensor/io/xio.hpp
@@ -17,6 +17,8 @@
 #include <sstream>
 #include <string>
 
+#include "xtl/xmasked_value_meta.hpp"
+
 #include "../core/xexpression.hpp"
 #include "../core/xmath.hpp"
 #include "../views/xstrided_view.hpp"
@@ -615,7 +617,8 @@ namespace xt
         struct printer<
             T,
             std::enable_if_t<
-                !xtl::is_fundamental<typename T::value_type>::value && !xtl::is_complex<typename T::value_type>::value>>
+                !xtl::is_fundamental<typename T::value_type>::value
+                && !xtl::is_complex<typename T::value_type>::value>>
         {
             using const_reference = typename T::const_reference;
             using value_type = std::decay_t<typename T::value_type>;
@@ -646,7 +649,14 @@ namespace xt
             void update(const_reference val)
             {
                 std::stringstream buf;
-                buf << val;
+                if constexpr (xtl::is_xmasked_value<value_type>::value)
+                {
+                    buf << +val;
+                }
+                else
+                {
+                    buf << val;
+                }
                 std::string s = buf.str();
                 if (int(s.size()) > m_width)
                 {
diff --git a/test/test_xmasked_view.cpp b/test/test_xmasked_view.cpp
index 14613d169..1c7f9cb4d 100644
--- a/test/test_xmasked_view.cpp
+++ b/test/test_xmasked_view.cpp
@@ -7,6 +7,8 @@
  * The full license is in the file LICENSE, distributed with this software. *
  ****************************************************************************/
 
+#include <sstream>
+
 #include "xtensor/io/xio.hpp"
 #include "xtensor/optional/xoptional_assembly.hpp"
 #include "xtensor/views/xmasked_view.hpp"
@@ -210,6 +212,21 @@ namespace xt
         EXPECT_EQ(data, expected2);
     }
 
+    TEST(xmasked_view, non_optional_data_stream)
+    {
+        const xarray<double> data = {{1., 5., 3.}, {4., 5., 6.}};
+        const xarray<bool> mask = {{true, false, false}, {false, true, false}};
+
+        const auto masked_data = masked_view(data, mask);
+
+        std::stringstream out;
+        out << masked_data;
+
+        const std::string expected = "{{     1, masked, masked},\n"
+                                     " {masked,      5, masked}}";
+        EXPECT_EQ(out.str(), expected);
+    }
+
     TEST(xmasked_view, assign)
     {
         xarray<double> data = {{1., -2., 3.}, {4., 5., -6.}, {7., 8., -9.}};

From c823a3fa4300bf1c3f390be91c475e5c1cd8c995 Mon Sep 17 00:00:00 2001
From: Alexis Placet <2400067+Alex-PLACET@users.noreply.github.com>
Date: Wed, 29 Apr 2026 09:23:51 +0200
Subject: [PATCH 2/2] formatting

---
 include/xtensor/io/xio.hpp | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/xtensor/io/xio.hpp b/include/xtensor/io/xio.hpp
index 2f31f9703..09ee4da58 100644
--- a/include/xtensor/io/xio.hpp
+++ b/include/xtensor/io/xio.hpp
@@ -17,11 +17,10 @@
 #include <sstream>
 #include <string>
 
-#include "xtl/xmasked_value_meta.hpp"
-
 #include "../core/xexpression.hpp"
 #include "../core/xmath.hpp"
 #include "../views/xstrided_view.hpp"
+#include "xtl/xmasked_value_meta.hpp"
 
 namespace xt
 {
@@ -617,8 +616,7 @@ namespace xt
         struct printer<
             T,
             std::enable_if_t<
-                !xtl::is_fundamental<typename T::value_type>::value
-                && !xtl::is_complex<typename T::value_type>::value>>
+                !xtl::is_fundamental<typename T::value_type>::value && !xtl::is_complex<typename T::value_type>::value>>
         {
             using const_reference = typename T::const_reference;
             using value_type = std::decay_t<typename T::value_type>;