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+Step 11: Adding Export Configuration
+====================================
+
+During :guide:`tutorial/Installing and Testing` of the tutorial we added the
+ability for CMake to install the library and headers of the project. During
+:guide:`tutorial/Packaging an Installer` we added the ability to package up
+this information so it could be distributed to other people.
+
+The next step is to add the necessary information so that other CMake projects
+can use our project, be it from a build directory, a local install or when
+packaged.
+
+The first step is to update our :command:`install(TARGETS)` commands to not
+only specify a ``DESTINATION`` but also an ``EXPORT``. The ``EXPORT`` keyword
+generates a CMake file containing code to import all targets listed in the
+install command from the installation tree. So let's go ahead and explicitly
+``EXPORT`` the ``MathFunctions`` library by updating the ``install`` command
+in ``MathFunctions/CMakeLists.txt`` to look like:
+
+.. literalinclude:: Complete/MathFunctions/CMakeLists.txt
+  :caption: MathFunctions/CMakeLists.txt
+  :name: MathFunctions/CMakeLists.txt-install-TARGETS-EXPORT
+  :language: cmake
+  :start-after: # install libs
+
+Now that we have ``MathFunctions`` being exported, we also need to explicitly
+install the generated ``MathFunctionsTargets.cmake`` file. This is done by
+adding the following to the bottom of the top-level ``CMakeLists.txt``:
+
+.. literalinclude:: Complete/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-install-EXPORT
+  :language: cmake
+  :start-after: # install the configuration targets
+  :end-before: include(CMakePackageConfigHelpers)
+
+At this point you should try and run CMake. If everything is setup properly
+you will see that CMake will generate an error that looks like:
+
+.. code-block:: console
+
+  Target "MathFunctions" INTERFACE_INCLUDE_DIRECTORIES property contains
+  path:
+
+    "/Users/robert/Documents/CMakeClass/Tutorial/Step11/MathFunctions"
+
+  which is prefixed in the source directory.
+
+What CMake is trying to say is that during generating the export information
+it will export a path that is intrinsically tied to the current machine and
+will not be valid on other machines. The solution to this is to update the
+``MathFunctions`` :command:`target_include_directories` to understand that it
+needs different ``INTERFACE`` locations when being used from within the build
+directory and from an install / package. This means converting the
+:command:`target_include_directories` call for ``MathFunctions`` to look like:
+
+.. literalinclude:: Step12/MathFunctions/CMakeLists.txt
+  :caption: MathFunctions/CMakeLists.txt
+  :name: MathFunctions/CMakeLists.txt-target_include_directories
+  :language: cmake
+  :start-after: # to find MathFunctions.h, while we don't.
+  :end-before: # should we use our own math functions
+
+Once this has been updated, we can re-run CMake and verify that it doesn't
+warn anymore.
+
+At this point, we have CMake properly packaging the target information that is
+required but we will still need to generate a ``MathFunctionsConfig.cmake`` so
+that the CMake :command:`find_package` command can find our project. So let's go
+ahead and add a new file to the top-level of the project called
+``Config.cmake.in`` with the following contents:
+
+.. literalinclude:: Step12/Config.cmake.in
+  :caption: Config.cmake.in
+  :name: Config.cmake.in
+
+Then, to properly configure and install that file, add the following to the
+bottom of the top-level ``CMakeLists.txt``:
+
+.. literalinclude:: Step12/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-install-Config.cmake
+  :language: cmake
+  :start-after: # install the configuration targets
+  :end-before: # generate the config file
+
+
+Next, we execute the :command:`configure_package_config_file`.  This command
+will configure a provided file but with a few specific differences from the
+standard :command:`configure_file` way.
+To properly utilize this function, the input file should have a single line
+with the text ``@PACKAGE_INIT@`` in addition to the content that is desired.
+That variable will be replaced with a block of code which turns set values into
+relative paths.  These values which are new can be referenced by the same name
+but prepended with a ``PACKAGE_`` prefix.
+
+.. literalinclude:: Step12/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-configure-package-config.cmake
+  :language: cmake
+  :start-after: # install the configuration targets
+  :end-before: # generate the version file
+
+The :command:`write_basic_package_version_file` is next.  This command writes
+a file which is used by :command:`find_package`, documenting the version and
+compatibility of the desired package.  Here, we use the ``Tutorial_VERSION_*``
+variables and say that it is compatible with ``AnyNewerVersion``, which
+denotes that this version or any higher one are compatible with the requested
+version.
+
+.. literalinclude:: Step12/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-basic-version-file.cmake
+  :language: cmake
+  :start-after: # generate the version file
+  :end-before: # install the generated configuration files
+
+Finally, set both generated files to be installed:
+
+.. literalinclude:: Step12/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-install-configured-files.cmake
+  :language: cmake
+  :start-after: # install the generated configuration files
+  :end-before: # generate the export
+
+At this point, we have generated a relocatable CMake Configuration for our
+project that can be used after the project has been installed or packaged. If
+we want our project to also be used from a build directory we only have to add
+the following to the bottom of the top level ``CMakeLists.txt``:
+
+.. literalinclude:: Step12/CMakeLists.txt
+  :caption: CMakeLists.txt
+  :name: CMakeLists.txt-export
+  :language: cmake
+  :start-after: # needs to be after the install(TARGETS) command
+
+With this export call we now generate a ``MathFunctionsTargets.cmake``, allowing the
+configured ``MathFunctionsConfig.cmake`` in the build directory to be used by
+other projects, without needing it to be installed.