Table – New Model

One of the major goals for the new table design (missed in the December 3 post) is to eliminate all the standalone code work functions (translate, encode, recreate, etc.), which require their definitions so that pointers to them can be put into the table entries.  Many of the codes do not have several of these work functions (for example, only commands have translate functions), and many codes share work functions (for example, all binary operator have the same recreate function).  Once all the codes are implemented, there would have been an explosion of these work functions, especially considering that each code will need a unique run function.

Therefore, a class hierarchy will be the basis for the new table model where the base class holds the information members and virtual functions used for these functions.  Using virtual functions allow defining common work functions in an upper class.  Unfortunately, there will be an explosion of classes since all codes need a unique run virtual function.  Fortunately, there is a way to define these classes without requiring every source file to know about them so only the base table class needs to be known globally, which will contain the interface for all of these derived classes.

There will be a table instance for each code containing the information for that code only.  Instead of identifying a code by an enumerator (essentially an index), a code will be identified by a base table class pointer.  Code information will be accessed by inline access functions, and the work functions accessed using virtual functions.  The index of the code will only be accessed when a token is finally encoded into the program.  Each code will be assigned a unique index during initialization (more on this later).  The token will therefore contain a code table instance pointer instead of a code enumerator (index).

Though there will no longer be a monolithic table instance, there will be some static table class members and functions.  For example, the search functions will be static since these will not require a table instance (they will return an instance for a code).  The search functions will use a static map member for looking up a name to get a code table instance.   Each of these static members will be described as they are created.