flex vs. lex timings for a C tokenizer which includes keywords:

Generation times:

	lex	    83.0 secs
	flex	     3.9
	flex -cfe    7.1	# uncompressed table, equivalence classes
	flex -cf    15.0	# uncompressed table, no equivalence classes

Scanner object file sizes:

	lex	   41.0K bytes
	flex	    9.4K
	flex -cfe  49.6K
	flex -cf  126.5K

Running times on a 28,088 line input (685K characters):

	lex	   29.8 secs
	flex	   19.3
	flex -cfe   9.0
	flex -cf    7.8

The timings were made on a Sun 3/60.  All times are user + system CPU time,
and don't include hashing of identifiers.

Summary:

    For about the same sized scanner, you get a factor of 3 in performance.
    For a 30% faster scanner, you get a scanner 1/4th the size, and it's
	generated in 1/20th the time.
    For a scanner that's 3 times larger, you get a factor of 3.8 in
	performance.
