added clang format

.clang-format

@@ -0,0 +1,5 @@
+---
+Language:     Cpp
+BasedOnStyle: Google
+ColumnLimit:  120
+SortIncludes: false

CMakeLists.txt

@@ -539,6 +539,23 @@ if(EIGEN_BUILD_BTL)
   add_subdirectory(bench/btl EXCLUDE_FROM_ALL)
 endif()
 
+find_package(CLANG_FORMAT 9 EXACT)
+if(CLANG_FORMAT_FOUND)
+set(FORMAT_SOURCES)
+list(APPEND FORMAT_SUBDIRS blas bench demos "doc" Eigen include lapack scripts share unsupported test failtest)
+foreach(DIR ${FORMAT_SUBDIRS})
+    set(ABS_DIR ${CMAKE_CURRENT_SOURCE_DIR}/${DIR})
+    file(GLOB_RECURSE ${DIR}_SOURCES ${ABS_DIR}/*.cc ${ABS_DIR}/*.h ${ABS_DIR}/*.cpp ${ABS_DIR}/*.hpp ${ABS_DIR}/*.c)
+    list(APPEND FORMAT_SOURCES ${${DIR}_SOURCES})
+  endforeach()
+    file(GLOB FORMAT_SOURCES_WITHOUTENDING LIST_DIRECTORIES false ${CMAKE_CURRENT_SOURCE_DIR}/Eigen/* ${CMAKE_CURRENT_SOURCE_DIR}/Eigen/CXX11/* ${CMAKE_CURRENT_SOURCE_DIR}/unsupported/Eigen/* ${CMAKE_CURRENT_SOURCE_DIR}/unsupported/Eigen/CXX11/*)
+    list(FILTER FORMAT_SOURCES_WITHOUTENDING EXCLUDE REGEX ".*.txt$")
+    list (APPEND FORMAT_SOURCES ${FORMAT_SOURCES_WITHOUTENDING})
+    add_custom_target(format
+    COMMAND ${CLANG_FORMAT_EXECUTABLE} -i -style=file ${FORMAT_SOURCES}
+    DEPENDS ${FORMAT_SOURCES})
+endif()
+
 if(NOT WIN32)
   add_subdirectory(bench/spbench EXCLUDE_FROM_ALL)
 endif()
@@ -577,6 +594,9 @@ if(PROJECT_IS_TOP_LEVEL)
     message(STATUS "check    | Build and run the unit-tests. Read this page:")
     message(STATUS "         |   http://eigen.tuxfamily.org/index.php?title=Tests")
   endif()
+  if(CLANG_FORMAT_FOUND)
+    message(STATUS "format   | Formats the source code according to .clang-format file")
+  endif()
   message(STATUS "blas     | Build BLAS library (not the same thing as Eigen)")
   message(STATUS "uninstall| Remove files installed by the install target")
   message(STATUS "---------+--------------------------------------------------------------")

cmake/FindCLANG_FORMAT.cmake

@@ -0,0 +1,61 @@
+
+
+# Find clang-format
+#
+# CLANG_FORMAT_EXECUTABLE   - Path to clang-format executable
+# CLANG_FORMAT_FOUND        - True if the clang-format executable was found.
+# CLANG_FORMAT_VERSION      - The version of clang-format found
+#
+# Copyright 2009-2020 The VOTCA Development Team (http://www.votca.org)
+#
+# Licensed under the Mozilla Public License Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.mozilla.org/en-US/MPL/2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+find_program(CLANG_FORMAT_EXECUTABLE
+             NAMES
+                   clang-format-9
+                   clang-format
+                   clang-format-11
+                   clang-format-10
+                   clang-format-8
+                   clang-format-7
+
+             DOC "clang-format executable")
+mark_as_advanced(CLANG_FORMAT_EXECUTABLE)
+
+# Extract version from command "clang-format -version"
+if(CLANG_FORMAT_EXECUTABLE)
+  execute_process(COMMAND ${CLANG_FORMAT_EXECUTABLE} -version
+                  OUTPUT_VARIABLE clang_format_version
+                  ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+  if(clang_format_version MATCHES "^.*clang-format version .*")
+    # clang_format_version sample: "clang-format version 3.9.1-4ubuntu3~16.04.1
+    # (tags/RELEASE_391/rc2)"
+    string(REGEX
+           REPLACE "^.*clang-format version ([.0-9]+).*"
+                   "\\1"
+                   CLANG_FORMAT_VERSION
+                   "${clang_format_version}")
+    # CLANG_FORMAT_VERSION sample: "3.9.1"
+  else()
+    set(CLANG_FORMAT_VERSION 0.0)
+  endif()
+else()
+  set(CLANG_FORMAT_VERSION 0.0)
+endif()
+
+include(FindPackageHandleStandardArgs)
+# handle the QUIETLY and REQUIRED arguments and set CLANG_FORMAT_FOUND to TRUE
+# if all listed variables are TRUE
+find_package_handle_standard_args(CLANG_FORMAT REQUIRED_VARS CLANG_FORMAT_EXECUTABLE VERSION_VAR CLANG_FORMAT_VERSION)