c++ - Trying to understand the C preprocessor -

Why do these blocks of code get different results?

Some common codes:

  #define PART1PART2 works #define STRINGAFY0 (s) #s #define STRINGAFY1 (s) STRINGAFY0 (s)  < / Pre> 
 Case 1: 
 
  # Defined GLUU (A, B, C) A ## B ## C STRING AFI1 (GLUU (Part 1, Part 2, *) ) / Yield "PTI1 PTR2 *"  
 
 Case 2: 
 
  #define GLUE (a, b) ##b ## * STRINGAFY1 ( GLUE (PART1, PART2) / yield "work *"  
 
 case 3: 
 
  # defined GLUE (A, B) A ## B STRINGAFY1 (GLUE (PART1, PART2 *)) / yield "PART1PART2 *"  
 
 I use MSVC ++ from VSNT2005 SP1 I am currently living. 
 
 EDIT: It is currently my belief that preprocessor works like this while expanding the macros: Step 1: - Move the body - ## Any white space around the operators Remove - Parsing the string, in this case an identifier is found which matches the name of a parameter: -If it is next to ## operator, then the identifier is replaced with the literal value due to the change parameter (y Ni is passed in the string) -If it is not ## next to the operator, then run this entire explanation process on the value of the parameter first, then replace the identifier with the result (Stranphi single '#' case Step 2: - Take that resulting string and parse it for any macros 
 
 Now, suppose that all 3 cases The result of the string as a result 
 
 PART1PART2 * 
 
 And so after step 2, the result of 
 
 works * 
 
 but very little Should result in less than one thing.