Table – New Code Type Enumeration

With the current table model, each entry contains a token type that identifies the type of token that is created for the table entry.  Each entry has a code enumerator, which is simply used as an index to the entry.  The code (index) is put into the program code.  The code enumeration was originally automatically generated from comments next to the table entries.  This avoided mismatches between the code enumerators and the table entries (though this was a poor design choice).  Only some entries were identified using these code enumerators.

For the new table model, each table entry will be a unique class with a unique instance.  Each table entry instance will be assigned a unique index by the base table entry constructor.  Some table entries will still need to be found be some means by the parser and translator.  This could be done directly by referencing the table entry instance, but this would require exposing the derived table entry classes.  The plan is only to expose the base table entry class definition.

To find these small number of table entries, an enumeration will still be used.  This enumeration will be similar to the token type enumeration currently given to each table entry.  Therefore a single Code Type enumeration will be defined and will also replace the token type enumeration.  Unlike the current Code enumeration, table entries could have the same Code Type enumerator (for example, all of the six variable codes will be assigned the Variable code type).  Only the first table entry assigned to a code type will be returned for a code type enumerator; the others will be assigned as alternate codes of the first.

Code types will generally not be assigned to table entries for commands, operators and functions (which will no longer be referred to as internal functions) except for a few cases (for example, the LET command and the equal operator).  New table flags will be assigned instead.  There is already a Command table flag, and there will be Operator and Function table flags.  Each of the codes with operands (variables, arrays, constants, defined functions, user functions, and subroutines) will have a code type.  There will not be separate enumerators for tokens with and without parentheses (more on this later).