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  Yueliang
  Lua implemented in Lua

  Copyright (c) 2005-2008 Kein-Hong Man <[email protected]>
  The COPYRIGHT file describes the conditions under which this
  software may be distributed (basically a Lua 5-style license.)

  Website: 	http://yueliang.luaforge.net/
  Project page: http://luaforge.net/projects/yueliang/

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INTRODUCTION

The goal of Yueliang is to implement Lua 5 in Lua 5. Such a codebase, if
well documented, can be a useful prototyping and educational tool.
Initially, the focus is on the front side of Lua, i.e. the lexical
analyzer, the parser and the code generator, in order to generate binary
chunks. Yueliang currently produces the exact binary chunk as the
original Lua 5 itself for Lua 5.0.3 and Lua 5.1.3. Yueliang is moon in
Mandarin.

A port of the back side (the VM) is being considered, but note that
there is a recent project on LuaForge called LuLu that does just this.

Note: the codebase is currently a no-brainer port of Lua's front side C
source code to Lua code, and the C heritage is retained as much as
possible to allow for easy comparison. Due to certain implementation
methods, processing might be slow (especially if the source file causes
a lot of string processing.) The initial version is not meant to be
fast. Even unused arguments are retained. Asserts are currently enabled.
While the Lua code itself is portable, portions of the code is
hard-coded to generate output for an x86-type platform (32-bit ints,
doubles, little-endian.)

See the test_lua directory for an automatic tester, test_scripts*.lua.
Only the lexer currently has a basic test suite. Performance for the
no-brainer port of the Lua 5.0.2 front end in Yueliang 0.1.0 is 28
seconds on an Athlon 2500+, or about 29.5KB/sec. (Native C is virtually
instantaneous, so a comparison is pointless, really.) I think a test
suite for the parser will be better than running it on random files. See
below for a list of todos.

For versions of Yueliang corresponding to older minor releases of Lua,
for example Lua 5.0.2 or Lua 5.1.1, please look at the README files in
each of the orig-5.* directory for information on the last version of
Yueliang corresponding to the particular Lua release.

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NOTES

* there is a failed assert in luaK:addk for both versions of lcode.lua,
  the assert is currently incorrectly written
* luaG_checkcode() in both versions of lparser.lua has currently not
  been implemented (better put in the runtime backend?)
* need to check compliance of lexers with recognizing characters beyond
  normal ASCII (accented characters) when used in identifiers

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WHAT'S NEW

Major changes for version 0.4.1 (details in the ChangeLog):
* Tested native 5.0.x and 5.1.x parsers with lots of test cases
* Fixed two bugs in native 5.1.x parser, # and % operator handling

Major changes for version 0.4.0 (details in the ChangeLog):
* A working native parser skeleton for Lua 5.1.x, plus code
  to deal with variable classification
* Sample parser log files covering all of the grammar

Major changes for version 0.3.2 (details in the ChangeLog):
* A working native lexer for Lua 5.1.x

Major changes for version 0.3.1 (details in the ChangeLog):
* Mark 2 of the native parser skeleton for 5.0.3 which does
  variable classification into locals, upvalues or globals
* Sample parser log files exercising variable classification

Major changes for version 0.3.0 (details in the ChangeLog):
* Native parser skeleton for 5.0.3 mostly works
* Sample parser log files covering all of the grammar

Older items can be found in OlderNews

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SOME SIZE STATS

Here are some 0.1.0 size statistics (note that embedding the sources is
redundant or pretty useless, as you will need an already present front
end to process the source code!) for the 6 files main in orig-5.0.3
minus luac.lua:

			Size	Zipped
Original sources*	130162	 29546
with LuaSrcDiet*	 48308	 13841
luac			108174	 32238
luac -s			 64930	 21867

*note: embedding these would be a little pointless

There are some more size stats in the README file in the nat-5.0.3
directory, for native lexers.

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IMPLEMENTATION PLAN

Here are some ideas, in no particular order or priority, with no
particular implementation time frame:

(a) A straight no-brainer port of Lua's front side C source code to
    Lua code, no optimization or heavy rewriting is done (MOSTLY DONE)
(b) A test suite for the lexer (MOSTLY DONE)
(c) A test suite for the:
    (i) parser (MOSTLY DONE)
    (ii) code generator (CAN ADAPT LUA'S TEST SUITE)
(d) Documentation for Lua code generation (STUDYING)
(e) A straight no-brainer port of Lua's back side C source code to
    Lua code, no optimization or heavy rewriting is done (ON HIATUS)
    *** NOTE: there is a Lua-on-Lua project called LuLu on LuaForge
(f) A test suite for the VM (CAN ADAPT LUA'S TEST SUITE)
(g) Partial rewrites of Yueliang. (NATIVE LEXERS AND PARSERS DONE
    FOR BOTH 5.0 AND 5.1)
(h) Addition of features to Yueliang.

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ACKNOWLEDGEMENTS

Yueliang is a straight port of Lua 5 code, so I have included the Lua
5.0.x copyright as well the Lua 5.1.x copyright files.

Thanks to the LuaForge people for hosting this.
Developed on SciTE http://www.scintilla.org/. Two thumbs up.

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FEEDBACK

Feedback and contributions are welcome. Your name will be acknowledged,
as long as you are willing to comply with COPYRIGHT. If your material is
self-contained, you can retain a copyright notice for those material in
your own name, as long as you use the same Lua 5/MIT-style copyright.

I am on dial-up, so I might not be able to reply immediately. My
alternative e-mail address is: keinhong AT gmail DOT com

Enjoy!!

Kein-Hong Man (esq.)
Kuala Lumpur
Malaysia 20080531