Flatten the math directory (#657)

.github/workflows/cpplint_modified_files.yml

@@ -30,19 +30,19 @@ jobs:
           print("cpplint:")
           print(subprocess.check_output(["cpplint"] + cpp_files).decode("utf-8"))
 
-          upper_files = [file for file in cpp_files if os.path.basename(file) != os.path.basename(file).lower()]
+          upper_files = [file for file in cpp_files if file != file.lower()]
           if upper_files:
             print("{} files contain uppercase characters:".format(len(upper_files)))
             print("\n".join(upper_files) + "\n")
 
-          space_files = [file for file in cpp_files if " " in os.path.basename(file) or "-" in file]
+          space_files = [file for file in cpp_files if " " in file or "-" in file]
           if space_files:
             print("{} files contain space or dash characters:".format(len(space_files)))
             print("\n".join(space_files) + "\n")
 
-          nodir_files = [file for file in cpp_files if os.sep not in file]
+          nodir_files = [file for file in cpp_files if file.count(os.sep) != 1]
           if nodir_files:
-            print("{} files are not in a directory:".format(len(nodir_files)))
+            print("{} files are not in one and only one directory:".format(len(nodir_files)))
             print("\n".join(nodir_files) + "\n")
 
           bad_files = len(upper_files + space_files + nodir_files)