https://github.com/firedragon91245/lua-5.4.6-custom
A modifyed version of the lua.org interpreter aiming to add new metatable functionality
https://github.com/firedragon91245/lua-5.4.6-custom
customization fork interpreter lua lua-interpreter
Last synced: about 2 months ago
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A modifyed version of the lua.org interpreter aiming to add new metatable functionality
- Host: GitHub
- URL: https://github.com/firedragon91245/lua-5.4.6-custom
- Owner: FireDragon91245
- Created: 2024-01-26T16:49:17.000Z (over 1 year ago)
- Default Branch: master
- Last Pushed: 2025-01-15T19:29:33.000Z (4 months ago)
- Last Synced: 2025-01-15T21:48:56.248Z (4 months ago)
- Topics: customization, fork, interpreter, lua, lua-interpreter
- Language: C
- Homepage:
- Size: 2.74 MB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# This is a modified version of the lua Interpreter
Original Version Lua 5.4.6 from [here](https://www.lua.org/)
[Download Page](https://www.lua.org/download.html)
[Direct Download](https://www.lua.org/ftp/lua-5.4.6.tar.gz)
## Modifications
- Added '__override' metamethod that is called when a existing key in a table is asigned a new value
- -> If __override exists gets called and the default asignment is cancled
Example:
```lua
local t = {}
setmetatable(t, {
__override = function(table, key, new_value, old_value)
print("override", key, new_value, old_value)
end
})
t.a = 1
print("a value", t.a)
t.a = 2 -- __override gets called default asignment is cancled
print("a value", t.a)
-- stdout:
-- a value 1
-- override a 2 1
-- a value 1
```
## Why?
**🤓 am actualy you can use proxy tables**
yes youre correct you can recreate __override with proxytables
```lua
local table = {}
local backing_table = {}
local proxy = {
__index = function (t, k)
return backing_table[k]
end,
__newindex = function (t, k, v)
if backing_table[k] then
print("override", k, v, backing_table[k])
else
backing_table[k] = v
end
end
}
setmetatable(table, proxy)
table.a = 1
print("a value", table.a)
table.a = 2
print("a value", table.a)
```
exact same output as __override
### BUT
try creating a proxyed proxy table on a table
this simple example:
```lua
local table = {}
local backing_table = {}
local proxy = {}
local backing_proxy = {
__newindex = function(self, key, value)
print("newindex in table")
backing_table[key] = value
end,
__index = function(self, key)
print("index in table")
return backing_table[key]
end
}
local proxy_proxy = {
__newindex = function(self, key, value)
print("newindex in proxy")
backing_proxy[key] = value
end,
__index = function(self, key)
print("index in proxy")
return backing_proxy[key]
end
}
setmetatable(proxy, proxy_proxy)
setmetatable(table, proxy)
table.a = 0
```
obviously this wont work because how would table know about its metatable
its metatable is the backing_proxy
so it would need to do table -> check for __index in its metatable (__index not found) -> ckeck if the metatable of table has a metatable and if that metatable of the metatable has __index (and this step lua wont do)
**🤓 am actualy you can use recursive __index by defining __index as a table in proxy**
yes you can define __index, in proxy to get a recusive call up to where you want but then the proxy table for __index wont work you cant detect if a __index is being overwritten becuase __index is already defined in proxy so __newindex of the poxy wont be called in the poxy_proxy
thats why __override exists, to make proxied proxy tables posible
by defining __override for the proxy you can catch __index for example, being overwritten
#### BUT WHY??!!
its for my lua-oop project it makes heavy use of scopes,
a scope is just another layer of metatable pushed infront of the current _ENV while the old scope is set as __index of the new scope,
so a scope could look like this (inner/current scope to outer/old scope)
{ class = { name = ""} } => (__index) => { myImportedValue = 1, somotherimport = false } => (__index) => _ENV
**but whats the problem?? why do you need proxied proxy tables?**
well what is when the user wants to define a custom metamethod??
well the user is out of luck, every _ENV already has the common metamethods because of the OOP scoping system so i implementetd "mmtables" (Muli Meta tables)
1 table can have more then 1 meta method of the same type by applying a poxy on the metatable, and because of the problem above a custom solution like __override is requred
# Original README
This is Lua 5.4.6, released on 02 May 2023.
For installation instructions, license details, and
further information about Lua, see doc/readme.html.