implement sub-interpreters

Author: Vipul-Cariappa

CMakeLists.txt

@@ -189,6 +189,7 @@ set(XEUS_CPP_SRC
     src/xparser.cpp
     src/xutils.cpp
     src/xmagics/os.cpp
+    src/xmagics/multi_interpreter.cpp
 )
 
 if(NOT EMSCRIPTEN)

src/xinterpreter.cpp

@@ -25,6 +25,8 @@
 #include "xparser.hpp"
 #include "xsystem.hpp"
 
+#include "xmagics/multi_interpreter.hpp"
+
 using Args = std::vector<const char*>;
 
 void* createInterpreter(const Args &ExtraArgs = {}) {
@@ -371,6 +373,7 @@ __get_cxx_version ()
         // preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("timeit",
         // timeit(&m_interpreter));
         // preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("python", pythonexec());
+        preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("subinterp", multi_interpreter());
         preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("file", writefile());
 #ifndef EMSCRIPTEN
         preamble_manager["magics"].get_cast<xmagics_manager>().register_magic("xassist", xassist());

src/xmagics/multi_interpreter.cpp

@@ -0,0 +1,93 @@
+/************************************************************************************
+ * Copyright (c) 2025, xeus-cpp contributors                                        *
+ *                                                                                  *
+ * Distributed under the terms of the BSD 3-Clause License.                         *
+ *                                                                                  *
+ * The full license is in the file LICENSE, distributed with this software.         *
+ ************************************************************************************/
+
+#include "multi_interpreter.hpp"
+
+#include <iostream>
+#include <iterator>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "CppInterOp/CppInterOp.h"
+
+static std::vector<std::string> split(const std::string& input)
+{
+    std::istringstream buffer(input);
+    std::vector<std::string> ret(
+        (std::istream_iterator<std::string>(buffer)),
+        std::istream_iterator<std::string>()
+    );
+    return ret;
+}
+
+static constexpr size_t len(std::string_view n)
+{
+    return n.size();
+}
+
+namespace xcpp
+{
+    void multi_interpreter::operator()(const std::string& line, const std::string& cell)
+    {
+        auto Args0 = split(line.substr(len("subinterp")));
+
+        Cpp::TInterp_t OldI = Cpp::GetInterpreter();  // we need to restore the old interpreter
+        Cpp::TInterp_t I = nullptr;
+        std::string name;
+        if (Args0[0] == "--use")
+        {
+            I = interpreters[Args0[1]];
+        }
+        else
+        {
+            auto named = std::find(Args0.begin(), Args0.end(), "--name");
+            if (named != Args0.end())
+            {
+                name = *(named + 1);
+            }
+        }
+
+        std::vector<const char*> Args(I ? 0 : Args0.size());
+        if (!I)
+        {
+            for (auto start = Args0.begin(), end = Args0.end(); start != end; start++)
+            {
+                if (*start == "--name")
+                {
+                    start++;
+                    continue;
+                }
+                Args.push_back((*start).c_str());
+            }
+        }
+
+        Cpp::BeginStdStreamCapture(Cpp::kStdErr);
+        Cpp::BeginStdStreamCapture(Cpp::kStdOut);
+        if (!I)
+        {
+            I = Cpp::CreateInterpreter(Args);  // TODO: error handling
+        }
+        if (I)
+        {
+            Cpp::Declare(cell.c_str(), false, I);
+        }
+        std::cout << Cpp::EndStdStreamCapture();
+        std::cerr << Cpp::EndStdStreamCapture();
+
+        if (!name.empty())
+        {
+            interpreters[name] = I;          // TODO: check if this is redefinition
+            Cpp::ActivateInterpreter(OldI);  // restoring old interpreter
+        }
+        else
+        {
+            Cpp::DeleteInterpreter(I);
+        }
+    }
+}  // namespace xcpp

src/xmagics/multi_interpreter.hpp

@@ -0,0 +1,33 @@
+/************************************************************************************
+ * Copyright (c) 2025, xeus-cpp contributors                                        *
+ *                                                                                  *
+ * Distributed under the terms of the BSD 3-Clause License.                         *
+ *                                                                                  *
+ * The full license is in the file LICENSE, distributed with this software.         *
+ ************************************************************************************/
+
+#ifndef XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP
+#define XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP
+
+#include <string>
+#include <unordered_map>
+
+#include "CppInterOp/CppInterOp.h"
+#include "xeus-cpp/xmagics.hpp"
+
+namespace xcpp
+{
+    class multi_interpreter : public xmagic_cell
+    {
+    public:
+
+        XEUS_CPP_API
+        void operator()(const std::string& line, const std::string& cell) override;
+
+    private:
+
+        std::unordered_map<std::string, Cpp::TInterp_t> interpreters;
+    };
+}  // namespace xcpp
+
+#endif  // XEUS_CPP_MULTI_INTERPRETER_MAGIC_HPP