feat: import std; support added

Resolves #595

conanfile.py

@@ -56,6 +56,7 @@ class MPUnitsConan(ConanFile):
     settings = "os", "arch", "compiler", "build_type"
     options = {
         "cxx_modules": [True, False],
+        "import_std": [True, False],
         "std_format": [True, False],
         "string_view_ret": [True, False],
         "no_crtp": [True, False],
@@ -64,6 +65,7 @@ class MPUnitsConan(ConanFile):
     }
     default_options = {
         # "cxx_modules" default set in config_options()
+        # "import_std" default set in config_options()
         # "std_format" default set in config_options()
         # "string_view_ret" default set in config_options()
         # "no_crtp" default set in config_options()
@@ -108,6 +110,10 @@ class MPUnitsConan(ConanFile):
                 "min_cppstd": "20",
                 "compiler": {"gcc": "", "clang": "17", "apple-clang": "", "msvc": ""},
             },
+            "import_std": {
+                "min_cppstd": "23",
+                "compiler": {"gcc": "", "clang": "18", "apple-clang": "", "msvc": ""},
+            },
             "static_constexpr_vars_in_constexpr_func": {
                 "min_cppstd": "23",
                 "compiler": {"gcc": "13", "clang": "17", "apple-clang": "", "msvc": ""},
@@ -128,6 +134,7 @@ class MPUnitsConan(ConanFile):
         return {
             "std_format": "std_format",
             "cxx_modules": "cxx_modules",
+            "import_std": "import_std",
             "string_view_ret": "static_constexpr_vars_in_constexpr_func",
             "no_crtp": "explicit_this",
         }
@@ -210,7 +217,7 @@ class MPUnitsConan(ConanFile):
                 self.requires("fmt/11.0.1")
 
     def build_requirements(self):
-        self.tool_requires("cmake/[>=3.29 <4]")
+        self.tool_requires("cmake/[>=3.30 <4]")
         if self._build_all:
             if not self.options.freestanding:
                 self.test_requires("catch2/3.6.0")
@@ -226,6 +233,16 @@ class MPUnitsConan(ConanFile):
             raise ConanInvalidConfiguration(
                 "'contracts' should be set to 'none' for a freestanding build"
             )
+        # mixing of `import std;` and regular header files includes does not work for now
+        if self.options.import_std:
+            if self.options.contracts != "none":
+                raise ConanInvalidConfiguration(
+                    "'contracts' should be set to 'none' to use `import std;`"
+                )
+            if not self.options.std_format:
+                raise ConanInvalidConfiguration(
+                    "'std_format' should be enabled to use `import std;`"
+                )
 
     def layout(self):
         cmake_layout(self)
@@ -242,6 +259,12 @@ class MPUnitsConan(ConanFile):
         if self.options.cxx_modules:
             tc.cache_variables["CMAKE_CXX_SCAN_FOR_MODULES"] = True
             tc.cache_variables["MP_UNITS_BUILD_CXX_MODULES"] = True
+        if self.options.import_std:
+            tc.cache_variables["CMAKE_CXX_MODULE_STD"] = True
+            # Current experimental support according to `Help/dev/experimental.rst`
+            tc.cache_variables[
+                "CMAKE_EXPERIMENTAL_CXX_IMPORT_STD"
+            ] = "0e5b6991-d74f-4b3d-a41c-cf096e0b2508"
         if self.options.freestanding:
             tc.cache_variables["MP_UNITS_API_FREESTANDING"] = True
         else:

docs/getting_started/installation_and_usage.md

@@ -237,6 +237,14 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 
     [conan C++ modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0
 
+[`import_std`](#import_std){ #import_std }
+
+:   [:octicons-tag-24: 2.3.0][conan import std support] · :octicons-milestone-24: `True`/`False` (Default: automatically determined from settings)
+
+    Enables `import std;` usage.
+
+    [conan import std support]: https://github.com/mpusz/mp-units/releases/tag/v2.3.0
+
 [`std_format`](#std_format){ #std_format }
 
 :   [:octicons-tag-24: 2.2.0][conan std::format support] · :octicons-milestone-24: `True`/`False` (Default: automatically determined from settings)
@@ -338,7 +346,14 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 
     Adds C++ modules to the list of default targets.
 
-    [build_cxx_modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0
+
+[`MP_UNITS_BUILD_IMPORT_STD`](#MP_UNITS_BUILD_IMPORT_STD){ #MP_UNITS_BUILD_IMPORT_STD }
+
+:   [:octicons-tag-24: 2.3.0][cmake import std support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`)
+
+    Enables `import std;` usage.
+
+    [cmake import std support]: https://github.com/mpusz/mp-units/releases/tag/v2.3.0
 
 [`MP_UNITS_API_STD_FORMAT`](#MP_UNITS_API_STD_FORMAT){ #MP_UNITS_API_STD_FORMAT }
 

example/avg_speed.cpp

@@ -25,8 +25,12 @@
 // !!! renders correctly in the documentation "Examples" section.                 !!!
 // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <exception>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/capacitor_time_curve.cpp

@@ -20,7 +20,11 @@
     physical_quantities
 */
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/clcpp_response.cpp

@@ -17,7 +17,11 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/conversion_factor.cpp

@@ -17,9 +17,13 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <iostream>
 #include <string>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/currency.cpp

@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include <mp-units/compat_macros.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <iostream>
 #include <map>
 #include <string_view>
 #include <utility>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units.core;
 #else

example/foot_pound_second.cpp

@@ -22,9 +22,13 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
 #include <string>
 #include <string_view>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/glide_computer.cpp

@@ -25,6 +25,9 @@
 #include <mp-units/bits/hacks.h>
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <chrono>
 #include <concepts>
@@ -33,6 +36,7 @@
 #include <ranges>
 #include <string>
 #include <utility>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/glide_computer_lib/glide_computer_lib.cpp

@@ -22,10 +22,14 @@
 
 #include "glide_computer_lib.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <functional>
 #include <iostream>
 #include <numeric>
 #include <string_view>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units.core;
 #else

example/glide_computer_lib/include/glide_computer_lib.h

@@ -25,6 +25,9 @@
 #include <mp-units/compat_macros.h>
 //
 #include "geographic.h"
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <algorithm>
 #include <array>
 #include <chrono>
@@ -35,6 +38,7 @@
 #include <ranges>
 #include <string>  // IWYU pragma: keep
 #include <vector>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/hello_units.cpp

@@ -27,8 +27,12 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iomanip>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/include/geographic.h

@@ -25,10 +25,14 @@
 #include "ranged_representation.h"
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>
 #include <limits>
 #include <numbers>
 #include <ostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/include/ranged_representation.h

@@ -26,9 +26,13 @@
 #include <mp-units/bits/hacks.h>
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <algorithm>
 #include <concepts>
 #include <type_traits>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units.core;
 #else

example/include/validated_type.h

@@ -26,9 +26,13 @@
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/contracts.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #include <ostream>
 #include <utility>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units.core;
 #else

example/kalman_filter/kalman.h

@@ -24,9 +24,13 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <algorithm>
 #include <locale>
 #include <tuple>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_1.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_2.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_3.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_4.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_5.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_6.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_7.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/kalman_filter/kalman_filter-example_8.cpp

@@ -22,8 +22,12 @@
 
 #include "kalman.h"
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/measurement.cpp

@@ -22,11 +22,15 @@
 
 #include <mp-units/bits/hacks.h>
 #include <mp-units/compat_macros.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cmath>
 #include <compare>  // IWYU pragma: export
 #include <exception>
 #include <iostream>
 #include <utility>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/si_constants.cpp

@@ -27,7 +27,11 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/spectroscopy_units.cpp

@@ -22,8 +22,12 @@
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
 #include <tuple>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/storage_tank.cpp

@@ -23,10 +23,14 @@
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
 #include <cassert>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <chrono>
 #include <iostream>
 #include <numbers>
 #include <string>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/strong_angular_quantities.cpp

@@ -20,7 +20,11 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/total_energy.cpp

@@ -20,8 +20,12 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <exception>
 #include <iostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

example/unmanned_aerial_vehicle.cpp

@@ -25,9 +25,13 @@
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
 #include <cassert>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #include <iostream>
 #include <string>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

src/CMakeLists.txt

@@ -38,9 +38,11 @@ check_libcxx_in_use(${projectPrefix}LIBCXX)
 # project build options
 option(${projectPrefix}BUILD_AS_SYSTEM_HEADERS "Exports library as system headers" OFF)
 option(${projectPrefix}BUILD_CXX_MODULES "Add C++ modules to the list of default targets" OFF)
+option(${projectPrefix}BUILD_IMPORT_STD "Enable `import std;` usage" OFF)
 
 message(STATUS "${projectPrefix}BUILD_AS_SYSTEM_HEADERS: ${${projectPrefix}BUILD_AS_SYSTEM_HEADERS}")
 message(STATUS "${projectPrefix}BUILD_CXX_MODULES: ${${projectPrefix}BUILD_CXX_MODULES}")
+message(STATUS "${projectPrefix}BUILD_IMPORT_STD: ${${projectPrefix}BUILD_IMPORT_STD}")
 
 if(${projectPrefix}BUILD_AS_SYSTEM_HEADERS)
     set(${projectPrefix}_AS_SYSTEM SYSTEM)
@@ -124,6 +126,15 @@ else()
     set(${projectPrefix}TARGET_SCOPE "INTERFACE")
 endif()
 
+if(${projectPrefix}BUILD_CXX_MODULES)
+    if(CMAKE_VERSION VERSION_LESS "3.30")
+        message(FATAL_ERROR "CMake versions before 3.30 do not support `import std;` properly")
+    endif()
+    if(CMAKE_CXX_STANDARD LESS 23)
+        message(FATAL_ERROR "`import std;` requires at lease C++23")
+    endif()
+endif()
+
 # components/modules
 include(MPUnitsContracts)
 add_subdirectory(core)

src/core/CMakeLists.txt

@@ -125,6 +125,14 @@ if(${projectPrefix}BUILD_CXX_MODULES)
     endif()
 endif()
 
+if(${projectPrefix}BUILD_IMPORT_STD)
+    target_compile_definitions(mp-units-core PUBLIC ${projectPrefix}IMPORT_STD)
+    # https://github.com/llvm/llvm-project/issues/75057
+    if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 19)
+        target_compile_options(mp-units-core PUBLIC "-Wno-deprecated-declarations")
+    endif()
+endif()
+
 # UTF-8 source and execution character set
 if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     target_compile_options(

src/core/include/mp-units/bits/core_gmf.h

@@ -43,6 +43,9 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
+#if __cpp_lib_text_encoding
+#include <text_encoding>
+#endif
 
 #if MP_UNITS_HOSTED
 #include <mp-units/ext/format.h>
@@ -53,7 +56,3 @@
 #include <sstream>
 #include <string>
 #endif
-
-#if __cpp_lib_text_encoding
-#include <text_encoding>
-#endif

src/core/include/mp-units/bits/fmt.h

@@ -37,12 +37,16 @@
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <concepts>
 #include <cstdint>
 #include <limits>
 #include <string_view>
 #endif
+#endif
 
 // most of the below code is based on/copied from fmtlib
 

src/core/include/mp-units/bits/ratio.h

@@ -28,10 +28,14 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #include <cstdint>
 #include <numeric>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/bits/text_tools.h

@@ -29,8 +29,12 @@
 #include <mp-units/framework/symbol_text.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/bits/type_list.h

@@ -25,10 +25,14 @@
 #include <mp-units/bits/hacks.h>  // IWYU pragma: keep
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstddef>
 #include <type_traits>
 #include <utility>
 #endif
+#endif
 
 MP_UNITS_DIAGNOSTIC_PUSH
 MP_UNITS_DIAGNOSTIC_IGNORE_EXPR_ALWAYS_TF

src/core/include/mp-units/ext/algorithm.h

@@ -29,10 +29,14 @@
 #include <mp-units/bits/hacks.h>  // IWYU pragma: keep
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>
 #include <initializer_list>
 #include <iterator>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/ext/fixed_string.h

@@ -33,17 +33,24 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #include <concepts>
 #include <cstddef>
 #include <cstdlib>
 #include <ranges>
 #include <string_view>
+#endif  // MP_UNITS_IMPORT_STD
+
 #if MP_UNITS_HOSTED
 #include <mp-units/ext/format.h>
+#ifndef MP_UNITS_IMPORT_STD
 #include <ostream>
 #endif
-#endif
+#endif  // MP_UNITS_HOSTED
+#endif  // MP_UNITS_IN_MODULE_INTERFACE
 
 MP_UNITS_EXPORT
 namespace mp_units {

src/core/include/mp-units/ext/format.h

@@ -36,7 +36,11 @@ MP_UNITS_DIAGNOSTIC_IGNORE_SHADOW
 #include <fmt/format.h>
 MP_UNITS_DIAGNOSTIC_POP
 #else
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <format>
 #endif
+#endif
 
 #endif

src/core/include/mp-units/ext/inplace_vector.h

@@ -28,10 +28,14 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstddef>
 #include <ranges>
 #endif
+#endif
 
 // NOLINTBEGIN(*-avoid-c-arrays)
 #pragma once

src/core/include/mp-units/ext/prime.h

@@ -28,6 +28,9 @@
 #include <mp-units/ext/algorithm.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <cstddef>
 #include <cstdint>
@@ -35,6 +38,7 @@
 #include <optional>
 #include <tuple>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/ext/type_name.h

@@ -6,8 +6,12 @@
 #pragma once
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <string_view>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/ext/type_traits.h

@@ -26,9 +26,13 @@
 #include <mp-units/bits/module_macros.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
 #include <utility>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/format.h

@@ -35,8 +35,12 @@
 #include <mp-units/framework/unit.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <locale>
 #endif
+#endif
 
 namespace mp_units::detail {
 

src/core/include/mp-units/framework/compare.h

@@ -26,8 +26,12 @@
 #include <mp-units/bits/module_macros.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>
 #endif
+#endif
 
 MP_UNITS_EXPORT
 namespace mp_units {

src/core/include/mp-units/framework/construction_helpers.h

@@ -28,8 +28,12 @@
 #include <mp-units/framework/representation_concepts.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/customization_points.h

@@ -27,10 +27,14 @@
 #include <mp-units/ext/type_traits.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <limits>
 #include <type_traits>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/dimension.h

@@ -37,6 +37,9 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <cstdint>
 #include <iterator>
@@ -44,7 +47,8 @@
 #if MP_UNITS_HOSTED
 #include <string>
 #endif
-#endif
+#endif  // MP_UNITS_IMPORT_STD
+#endif  // MP_UNITS_IN_MODULE_INTERFACE
 
 namespace mp_units {
 

src/core/include/mp-units/framework/expression_template.h

@@ -28,9 +28,13 @@
 #include <mp-units/ext/type_traits.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #include <functional>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/magnitude.h

@@ -36,12 +36,16 @@
 #include <mp-units/framework/symbol_text.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstdint>
 #include <cstdlib>
 #include <numbers>
 #include <optional>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/quantity.h

@@ -39,9 +39,13 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #include <utility>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/quantity_cast.h

@@ -29,8 +29,12 @@
 #include <mp-units/framework/reference.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
 #endif
+#endif
 
 MP_UNITS_EXPORT
 namespace mp_units {

src/core/include/mp-units/framework/quantity_point.h

@@ -31,8 +31,12 @@
 #include <mp-units/framework/quantity_point_concepts.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/quantity_spec.h

@@ -38,11 +38,15 @@
 #include <mp-units/framework/representation_concepts.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstdint>
 #include <tuple>
 #include <type_traits>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/reference.h

@@ -31,8 +31,12 @@
 #include <mp-units/framework/representation_concepts.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/representation_concepts.h

@@ -27,11 +27,15 @@
 #include <mp-units/framework/customization_points.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstdint>
 #include <functional>
 #include <type_traits>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/framework/symbol_text.h

@@ -32,15 +32,23 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <compare>  // IWYU pragma: export
 #include <cstddef>
 #include <cstdint>
 #endif
+#endif
 
 #if __cpp_lib_text_encoding
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <text_encoding>
 #endif
+#endif
 static_assert(std::text_encoding::literal().mib() == std::text_encoding::id::UTF8);
 #endif
 

src/core/include/mp-units/framework/unit.h

@@ -43,6 +43,9 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/ext/contracts.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <cstdint>
 #include <iterator>
@@ -50,7 +53,8 @@
 #if MP_UNITS_HOSTED
 #include <string>
 #endif
-#endif
+#endif  // MP_UNITS_IMPORT_STD
+#endif  // MP_UNITS_IN_MODULE_INTERFACE
 
 namespace mp_units {
 

src/core/include/mp-units/math.h

@@ -32,10 +32,14 @@
 #include <mp-units/framework/value_cast.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cmath>
 #include <cstdint>
 #include <limits>
 #endif
+#endif
 
 MP_UNITS_EXPORT
 namespace mp_units {

src/core/include/mp-units/ostream.h

@@ -30,9 +30,13 @@
 #include <mp-units/framework/unit.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #include <sstream>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/include/mp-units/random.h

@@ -26,9 +26,11 @@
 #include <mp-units/framework/quantity.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
+#ifndef MP_UNITS_IMPORT_STD
 #include <functional>
 #include <random>
 #endif
+#endif
 
 namespace mp_units {
 

src/core/mp-units-core.cpp

@@ -22,10 +22,16 @@
 
 module;
 
+#ifndef MP_UNITS_IMPORT_STD
 #include <mp-units/bits/core_gmf.h>
+#endif
 
 export module mp_units.core;
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#endif
+
 #define MP_UNITS_IN_MODULE_INTERFACE
 
 #include <mp-units/compat_macros.h>

src/systems/include/mp-units/systems/angular/math.h

@@ -32,8 +32,12 @@
 #include <mp-units/framework/quantity.h>
 #include <mp-units/framework/unit.h>
 #include <mp-units/framework/value_cast.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cmath>
 #endif
+#endif
 
 
 MP_UNITS_EXPORT

src/systems/include/mp-units/systems/si/chrono.h

@@ -32,8 +32,12 @@
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 #include <mp-units/framework/customization_points.h>
 #include <mp-units/framework/quantity_point.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <chrono>
 #endif
+#endif
 
 namespace mp_units {
 

src/systems/include/mp-units/systems/si/math.h

@@ -33,8 +33,12 @@
 #include <mp-units/framework/quantity.h>
 #include <mp-units/framework/unit.h>
 #include <mp-units/framework/value_cast.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cmath>
 #endif
+#endif
 
 
 MP_UNITS_EXPORT

src/systems/mp-units-systems.cpp

@@ -22,12 +22,17 @@
 
 module;
 
+#ifndef MP_UNITS_IMPORT_STD
 #include <mp-units/bits/core_gmf.h>
 #include <chrono>
+#endif
 
 export module mp_units.systems;
 
 export import mp_units.core;
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#endif
 
 #define MP_UNITS_IN_MODULE_INTERFACE
 

test/runtime/atomic_test.cpp

@@ -21,7 +21,11 @@
 // SOFTWARE.
 
 #include <catch2/catch_test_macros.hpp>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <atomic>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/distribution_test.cpp

@@ -21,12 +21,16 @@
 // SOFTWARE.
 
 #include <catch2/catch_test_macros.hpp>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <cstddef>
 #include <cstdint>
 #include <initializer_list>
 #include <random>
 #include <vector>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/fixed_string_test.cpp

@@ -24,8 +24,12 @@
 #include <catch2/matchers/catch_matchers_exception.hpp>
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <sstream>
 #include <string_view>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/fmt_test.cpp

@@ -25,6 +25,9 @@
 #include <catch2/matchers/catch_matchers_exception.hpp>
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #include <iomanip>
 #include <limits>
@@ -32,6 +35,7 @@
 #include <sstream>
 #include <string>
 #include <string_view>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/linear_algebra_test.cpp

@@ -23,8 +23,12 @@
 #include <catch2/catch_test_macros.hpp>
 #include <mp-units/compat_macros.h>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <matrix>
 #include <ostream>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/math_test.cpp

@@ -23,7 +23,11 @@
 #include "almost_equals.h"
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers.hpp>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <limits>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/runtime/truncation_test.cpp

@@ -25,8 +25,12 @@
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers.hpp>
 #include <mp-units/ext/format.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <limits>
 #include <numbers>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/static/angular_test.cpp

@@ -21,7 +21,11 @@
 // SOFTWARE.
 
 #include <mp-units/systems/isq_angle.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <numbers>
+#endif
 
 namespace {
 

test/static/chrono_test.cpp

@@ -25,9 +25,13 @@
 #include <mp-units/framework/quantity_point.h>  // IWYU pragma: keep
 #include <mp-units/systems/isq/si_quantities.h>
 #include <mp-units/systems/si.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <chrono>
 #include <concepts>
 #include <ratio>
+#endif
 
 namespace {
 

test/static/concepts_test.cpp

@@ -23,6 +23,9 @@
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/natural.h>
 #include <mp-units/systems/si.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <optional>
 #include <type_traits>
 #if MP_UNITS_HOSTED
@@ -30,6 +33,7 @@
 #include <complex>
 #include <string>
 #endif
+#endif
 
 #if MP_UNITS_HOSTED
 template<typename T>

test/static/custom_rep_test_min_expl.cpp

@@ -20,8 +20,12 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <ostream>
 #include <type_traits>
+#endif
 #ifdef MP_UNITS_MODULES
 import mp_units;
 #else

test/static/custom_rep_test_min_impl.cpp

@@ -24,8 +24,12 @@
 #include <mp-units/framework.h>
 #include <mp-units/systems/si/prefixes.h>
 #include <mp-units/systems/si/units.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/dimension_symbol_test.cpp

@@ -22,7 +22,11 @@
 
 #include <mp-units/framework.h>
 #include <mp-units/systems/isq.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <string_view>
+#endif
 
 namespace {
 

test/static/dimension_test.cpp

@@ -23,7 +23,11 @@
 #include "test_tools.h"
 #include <mp-units/ext/type_traits.h>
 #include <mp-units/framework.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/fixed_string_test.cpp

@@ -21,8 +21,12 @@
 // SOFTWARE.
 
 #include <mp-units/ext/fixed_string.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <string_view>
+#endif
 
 using namespace mp_units;
 

test/static/prime_test.cpp

@@ -21,9 +21,13 @@
 // SOFTWARE.
 
 #include <mp-units/ext/prime.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <array>
 #include <cstddef>
 #include <utility>
+#endif
 
 using namespace mp_units::detail;
 

test/static/quantity_point_test.cpp

@@ -26,6 +26,9 @@
 #include <mp-units/systems/isq.h>
 #include <mp-units/systems/si.h>
 #include <mp-units/systems/usc.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstdint>
 #include <limits>
@@ -34,6 +37,7 @@
 #if MP_UNITS_HOSTED
 #include <chrono>
 #endif
+#endif
 
 namespace {
 

test/static/quantity_spec_test.cpp

@@ -23,7 +23,11 @@
 #include "test_tools.h"
 #include <mp-units/ext/type_traits.h>
 #include <mp-units/framework.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/quantity_test.cpp

@@ -27,6 +27,9 @@
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <concepts>
 #include <cstdint>
 #include <limits>
@@ -35,6 +38,7 @@
 #if MP_UNITS_HOSTED
 #include <chrono>
 #endif
+#endif
 
 template<>
 inline constexpr bool mp_units::is_vector<int> = true;

test/static/reference_test.cpp

@@ -23,8 +23,12 @@
 #include "test_tools.h"
 #include <mp-units/framework.h>
 #include <mp-units/systems/si/prefixes.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <cstdint>
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/si_test.cpp

@@ -21,7 +21,11 @@
 // SOFTWARE.
 
 #include <mp-units/systems/si.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/test_tools.h

@@ -24,7 +24,11 @@
 
 #include <mp-units/bits/hacks.h>
 #include <mp-units/framework/quantity_spec.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 template<auto V, typename T>
 inline constexpr bool is_of_type = std::is_same_v<MP_UNITS_REMOVE_CONST(decltype(V)), T>;

test/static/type_list_test.cpp

@@ -22,7 +22,11 @@
 
 #include <mp-units/bits/type_list.h>
 #include <mp-units/ext/type_traits.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 namespace {
 

test/static/unit_symbol_test.cpp

@@ -23,7 +23,11 @@
 #include <mp-units/systems/iau.h>
 #include <mp-units/systems/iec80000.h>
 #include <mp-units/systems/si.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <string_view>
+#endif
 
 namespace {
 

test/static/unit_test.cpp

@@ -24,7 +24,11 @@
 #include <mp-units/ext/type_traits.h>
 #include <mp-units/framework.h>
 #include <mp-units/systems/si/prefixes.h>
+#ifdef MP_UNITS_IMPORT_STD
+import std;
+#else
 #include <type_traits>
+#endif
 
 namespace {