Program – Dereference Removed Lines

When a line of code is replaced or removed, the use counts of any dictionary entries referenced on the line need to be decremented.  If the use counts becomes zero, the entry is no longer being used and needs to be deleted from the dictionary (the entry becomes available for use by another item upon the next add).

The dereference routine was added to the program model to scan a line that is about to be replaced or removed.  This routine loops through each program word of the line and removes the reference for any code that has an operand, which is determined by whether the code has a remove function.  In the update line routine, this routine is called before the line is replaced or removed.

Table entry remove functions were added for the various REM, constant and variable codes.  Each remove function calls the remove routine of appropriate dictionary (just like the encode function calls the add routine of appropriate dictionary to add a reference).

Encoder test #2 contains replace and remove operations, but previously the use counts of dictionary entries were not being decremented.  Now that they are, several dictionary entries are now removed since their uses counts become zero and are removed from the dictionary.  This allowed new items to be added in the unused entries, which affected the index of several dictionary entries on some of the program lines, therefore the expected results were updated.

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