Re-enable all examples

examples/CMakeLists.txt

@@ -1,11 +1,42 @@
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+# # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+# Define a list
 set(ALL_EXAMPLES
-  #identity_as_default_projection
-identity_direct_usage)
+  identity_direct_usage 17
+  identity_as_default_projection 20)
 
-foreach(example ${ALL_EXAMPLES})
+file(MAKE_DIRECTORY ${CMAKE_BINARY_DIR}/tmp)
+
+# Iterate over the list in steps of 2
+list(LENGTH ALL_EXAMPLES ALL_EXAMPLES_LENGTH)
+math(EXPR LAST_INDEX "${ALL_EXAMPLES_LENGTH} - 1")
+foreach(i RANGE 0 ${LAST_INDEX} 2)
+  list(GET ALL_EXAMPLES "${i}" example)                      # Get the example name
+  math(EXPR cpp_standard_index "${i} + 1")
+  list(GET ALL_EXAMPLES ${cpp_standard_index} cpp_standard)  # Get the C++ standard for that example
+  message(STATUS "Try compile example: ${example} cpp_standard: ${cpp_standard}")
+
+  # Try to compile the example. Continue to the next example if compilation fails.
+  try_compile(
+    COMPILE_SUCCESS
+    ${CMAKE_BINARY_DIR}/tmp
+    ${CMAKE_CURRENT_SOURCE_DIR}/${example}.cpp
+    CMAKE_FLAGS
+      -DCMAKE_CXX_STANDARD=${cpp_standard}
+      -DCMAKE_CXX_STANDARD_REQUIRED=YES
+      -DCMAKE_CXX_EXTENSIONS=NO
+      -DCMAKE_CXX_FLAGS="-I${CMAKE_CURRENT_SOURCE_DIR}/../include" # does not work
+    OUTPUT_VARIABLE COMPILE_OUTPUT  # Capture output
+  )
+  message(STATUS "Compile output: ${COMPILE_OUTPUT}") # debug
+  if (NOT COMPILE_SUCCESS)
+    message(WARNING "Skipping ${example}: Requires C++${cpp_standard} or later")
+    continue()
+  endif()
+
+  # Add executable and link to the target.
   add_executable(beman.exemplar.examples.${example})
   target_sources(beman.exemplar.examples.${example} PRIVATE ${example}.cpp)
   target_link_libraries(beman.exemplar.examples.${example} beman::exemplar)
+  target_compile_features(beman.exemplar.examples.${example} PRIVATE cxx_std_${cpp_standard})
 endforeach()