Improved comments.
Parser for BY - FROM/DOWNFROM - DOWNTO/ABOVE.
Parser for BY - DOWNTO/ABOVE - FROM/DOWNFROM.
Name the parsers differently.
Parser for DOWNTO/ABOVE - FROM/DOWNFROM - BY.
Parser for DOWNTO/ABOVE - BY - FROM/DOWNFROM.
Parser for DOWNFROM - TO/DOWNTO/ABOVE - BY.
Parser for DOWNFROM - BY - TO/DOWNTO/ABOVE.
Parser for  TO/DOWNTO/ABOVE - DOWNFROM - BY.
Parser for  TO/DOWNTO/ABOVE - BY - DOWNFROM.
Parser for BY - DOWNFROM - TO/DOWNTO/ABOVE.
Parser for BY - TO/DOWNTO/ABOVE - DOWNFROM.