Hashed local symbol table

Hash tables can clearly implement 'lookup' and 'insert' operations. For implementing the 'delete', we do not want to scan the entire hash table looking for lists containing entries to be deleted. Each entry should have two links:

a) A hash link that chains the entry to other entries whose names hash to the same value - the usual link in the hash table.

b) A scope link that chains all entries in the same scope - an extra link. If the scope link is left undisturbed when an entry is deleted from the hash table, then the chain formed by the scope links will constitute an inactive symbol table for the scope in question.