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+nat-5.0.3
+
+This directory contains versions of front end files that are rewritten
+to be more "native" to Lua. These files should be considered as
+exercises in exploring ways to write the front end, for example, to
+write a front end that is optimized for size, etc. See also file size
+data further below.
+
+The following are the different versions available (mk2 == "mark 2",
+this is commonly used in the UK, e.g. for aeroplanes during WWII):
+
+Lexers
+------
+
+WARNING: Theses lexer may or may not exhibit exact behaviour when lexing
+strings or long strings with embedded CRLF newlines. The CRLF sequence
+may be translated into LF (the reference manual is unclear on this.) The
+user is advised to stick to LF line endings exclusively.
+
+llex_mk2        Rewritten from original ported code to become more
+                Lua-like. Still uses a stream-based input interface.
+                MK2 still scans using a per-character function that
+                is pretty inefficient.
+
+                Status: TESTED
+
+llex_mk3        A rewritten version of MK2 that needs input to be
+                entered as a single string. Unless an application's
+                need is very unusual, this should not be a problem.
+                It will not work for per-line interaction, though.
+                MK3 no longer needs stream input functions. This
+                version is also heavily optimized for size. MK3 scans
+                using find functions and doesn't create many strings.
+
+                Status: TESTED
+
+llex_mk4        A rewritten version of MK3 that is line-oriented.
+                This allows a command-line version that works in the
+                usual way to be written.
+
+                Status: TESTED
+
+The following is a comparison of file sizes (as of 20061111):
+
+                 lzio    llex    TOTAL  Speed (2)
+                (bytes) (bytes) (bytes) (KB/s)
+----------------------------------------------
+Binary (Mingw)    416    5312    5728     N/A
+----------------------------------------------
+(in orig-5.0.3:)
+----------------------------------------------
+normal           2219   12639   14585    404.9
+stripped         1292    7618    8910
+----------------------------------------------
+(in nat-5.0.3:)
+----------------------------------------------
+mk2              1995    7628    9623    469.5
+mk2-stripped     1195    4003    5298
+----------------------------------------------
+mk3 (1)             -    6552    6552   1870.8
+mk3-stripped        -    3286    3286
+----------------------------------------------
+mk4              1337    6956    8293    802.9
+mk4-stripped      798    3457    4225
+----------------------------------------------
+
+(1) mk3 does not have a file input streaming function
+
+(2) Speed was benchmarked using a Sempron 3000+. Benchmark scripts are
+in the test directories. Best of first three figures quoted. This is a
+measurement of raw lexer speed, i.e. tokens are read but no processing
+is done. All files are read in entirely before running the lexer.
+
+The performance of the orig-5.0.3 parser is probably a whole magnitude
+less than the orig-5.0.3 lexer performance.
+
+Parsers
+-------
+
+lparser_mk3     Written for the simplified lexer interface of llex_mk3+.
+                (Should be compatible with llex_mk4 too, but untested.)
+                This is a lexer skeleton, stripped of codegen code. See
+                the comments in the source code for more information.
+                Without logging messages and comments, it's under 600 LOC.
+
+                Sample output of the parser message logger can be found
+                in the test/parser_log subdirectory.
+
+                Tested with test_parser-5.0.lua, the Lua 5.0.x parser test
+                cases in the test_lua/ directory, appears to be fine.
+
+                Status: SNIPPETS APPEAR TO WORK
+
+lparser_mk3b    As above, with variable management code added. In order
+                to use the parser usefully, variable management code is
+                a big step forward, allowing the parser to differentiate
+                locals, upvalues and globals. The number of added lines
+                is around 100 LOC. A binary chunk of lparser_mk3b
+                (stripped) is 18076 bytes.
+
+                Sample output of the parser message logger can be found
+                in the test/parser_log subdirectory.
+
+                Tested with test_parser-5.0.lua, the Lua 5.0.x parser test
+                cases in the test_lua/ directory, appears to be fine.
+
+                Status: SNIPPETS APPEAR TO WORK
+
+There will be no further development beyond lparser_mk3b. Further work
+will focus on a 5.1.x equivalent, for which both a parser skeleton and a
+parser with full code generation using nicely commented code is planned.
+
+Other notes:
+------------
+
+For Lua 5.0.2, see Yueliang 0.1.3, which was the last release of Lua
+5.0.2 material.
+
+Test scripts for the lexer should probably be consolidated, but it's a
+little difficult because not all lexers give the same error messages or
+use the same token names or format.
+