Jua: simplified Lua implemented in Java

[kyle-ip]

Introduction

Jua is a simplified Lua (5.3) implementation written in Java.

The purpose of building this project is to learn:

• Data Structure
• Register-based Virtual Machine & Instruction Set Design
• Compilers
• Lua Standard Libraries

Features

• Virtual Machine: (Instruction Set & Runner)
• Compiler: Lexer, AST Parser & Code Generator
• Standard Libraries
• Metaprogramming

All of the features above are mentioned above in pure Java.

As I become more familiar with Compiling, I plan to use Antlr and LLVM to refactor it.

To-Do List

• Label & Goto statement
• Userdata
• Coroutines Support
• Garbage Collector
• Standard Libraries:
  • basic library
  • mathematical functions
  • string manipulation
  • package library
  • input and output
  • basic UTF-8 support
  • debug facilities
  • table manipulation
  • operating system facilities
  • coroutine library
• REPL
• Other interesting features

Some brief thoughts about Coroutine:

Coroutine is not supported in pure Java, so we need to implement a Thread-based or Bytecode-based coroutine scheduler for Jua.

We can also utilize Kotlin Coroutine. Kotlin code can be easily called from Java.

But in that case, why don't we just implement Jua in Kotlin completely?

Another solution is OpenJDK project Loom, which is supported by HotSpot Group:

https://openjdk.org/projects/loom

Standard Library

Follow the specification of

http://www.lua.org/manual/5.3/manual.html

Jua provides the standard library functions as below:

Basic

No.	Function	Synopsis
0	print	print (···)
1	assert	assert (v [, message])
2	error	error (message [, level])
3	select	select (index, ···)
4	ipairs	ipairs (t)
5	pairs	pairs (t)
6	next	next (table [, index])
7	load	load (chunk [, chunkname [, mode [, env]]])
8	loadfile	loadfile ([filename [, mode [, env]]])
9	dofile	dofile ([filename])
10	pcall	pcall (f [, arg1, ···])
11	xpcall	xpcall (f, msgh [, arg1, ···])
12	getmetatable	getmetatable (object)
13	setmetatable	setmetatable (table, metatable)
14	rawequal	rawequal (v1, v2)
15	rawlen	rawlen (v)
16	rawget	rawget (table, index)
17	rawset	rawset (table, index, value)
18	type	type (v)
19	tostring	tostring (v)
20	tonumber	tonumber (e [, base])
...

Math

No.	Function	Synopsis
0	random	math.random ([m [, n]])
1	randomseed	math.randomseed (x)
2	max	math.max (x, ···)
3	min	math.min (x, ···)
4	exp	math.exp (x)
5	log	math.log (x [, base])
6	deg	math.deg (x)
7	rad	math.rad (x)
8	sin	math.sin (x)
9	cos	math.cos (x)
10	tan	math.tan (x)
11	asin	math.asin (x)
12	acos	math.acos (x)
13	atan	math.atan (y [, x])
14	ceil	math.ceil (x)
15	floor	math.floor (x)
16	abs	math.abs (x)
17	sqrt	math.sqrt (x)
18	fmod	math.abs (x)
19	modf	math.modf (x)
20	ult	math.ult (m, n)
21	tointeger	math.tointeger (x)
22	type	math.type (x)
23	pi	The value of π.
24	huge	A value larger than any other numeric value.
25	maxinteger	An integer with the maximum value for an integer.
26	mininteger	An integer with the minimum value for an integer.
...

String

No.	Function	Synopsis
0	len	string.len (s)
1	rep	string.rep (s, n [, sep])
2	lower	string.lower (s)
3	upper	string.upper (s)
...

Modules

No.	Function	Synopsis
0	require	require (modname)
1	searchers	package.searchers
2	searchpath	package.searchpath (name, path [, sep [, rep]])
...

...

Usage

Dependencies

• JDK 1.8+
• Maven 3+

Build Project

To clone the source code and execute the following command to build the package:

https://github.com/kyle-ip/Jua

git clone https://github.com/kyle-ip/Jua.git
cd Jua
mvn clean package

Alternatively, you can also download the QuickStart package for testing:

https://github.com/kyle-ip/Jua/releases/download/v5.3.5-alpha/jua-5.3.5-alpha.jar

Run script

Edit sum.lua and execute:

function sum()
    local s = 0
    for i = 1, 100 do
        if i % 2 == 0 then
            s = s + math.sqrt(i)
        end
    end
    return s
end
print(sum())
java -jar jua-5.3.5-alpha.jar sum.lua

Result:

             ,---._
           .-- -.' \
           |    |   :
           |    |   |         ,--,
           |    |   |       ,'_ /|
           |    |   |  .--. |  | :    ,--.--.
           |    |   |,'_ /| :  . |   /       \
           |    |   ||  ' | |  . .  .--.  .-. |
       ___ |    |   ||  | ' |  | |   \__\/| . .
     /    /\    |   ||  | : ;  ; |   ," .--.; |
    /  ../  `..-    ,|  |  `--'   \ /  /  ,.  |
    \    \         ; :  ,      .-./;  :  |..'  \
     \    \      ,'   `--`----'    |  ,     .-./
      "---....--'                   `--`---'
    :: jua ::                      (5.3.5-alpha)

338.048

References

• lua.go
• Lua 5.3 Reference Manual
• Lua 5.3 Test suites
• ...

If you want to learn more about how to build your own programming language, please refer to these friendly guide books:

https://book.douban.com/subject/27034273

https://book.douban.com/subject/30303705

https://book.douban.com/subject/30348061

License

MIT License

See LICENSE.txt