###Simple C++ Pre Compiler A lab belonging to the OOP course. Don't ever think of using it for complex preprocessor directives.

#PART 1. Preprocessor Directives ###MACROS - USAGE - SCENCRIO #INCLUDE Tells the preprocessor to treat the contents of a specified file as if they appear in the source program at the point where the directive appears.

 #include   "path-spec" 
 #include   < path-spec >

#DEFINE The #define creates a macro, which is the association of an identifier or parameterized identifier with a token string. After the macro is defined, the compiler can substitute the token string for each occurrence of the identifier in the source file.

 #define identifier token-stringopt

#UNDEF Removes (undefines) a name previously created with #define.

 #undef identifier

#IFDEF **#IFNDEF ** The #ifdef and #ifndef directives perform the same task as the #if directive when it is used with defined( identifier ).

 #ifdef identifier
 #ifndef identifier

#IF #ELSE #ENDIF #ELIF The #if directive, with the #elif, #else, and #endif directives, controls compilation of portions of a source file. If the expression you write (after the #if) has a nonzero value, the line group immediately following the #if directive is retained in the translation unit.

#if defined(CREDIT)
    credit();
#elif defined(DEBIT)
    debit();
#else
    printerror();
#endif

#PART 2. Implementation ###My project is a Visual Studio solution.

1. The PreCompiler (PreCompiler.cpp) first takes in a streamed code file, preprocessed by Serializer (serializer.h) into a structurized model.

2. Code fragments are abstracted into three types – MACRO, STATEMENT and BLOCK. They are all inherited from BASEMODEL (model.h).

   STMT Statements ended with “;”.

   MACRO Preprocessor directives starting with “#”.

   BLOCK The file can be viewed as a BLOCK. if-else, functions, classes are also interpreted into a BLOCK. A BLOCK has two fields – content (optional, if-else conditions, function params) and context vector (STMTs, MACROs, BLOCKs embedded in the block).

3. The serialized code is then processed by a Processor (stmtp.h) one after another. There is a def_trans_map in macrop.h, which records macro definitions already met. macrop.add_macro takes in mcro string and converts it into structured key-value pair. macrop.process process each statement and replace embedded macro identifiers. Other complex directives are handled by stmtp.process.

4. After the code cleaned up, a Streamlizer (streamlizer.h) turns the structured document back to a streamed file with a nice format. And the PreCompiler writes it back into the disk.

#PART 3. Examples The given demo.cpp and outputted out.cpp.