Re: Lua as a data description language

[Dimitris Papavasiliou <jimmyp@...>]

Asko Kauppi wrote:

> Couldn't a new bytecode be introduced (by Lua authors) that would take 
> less space than current ones.  This solution would be totally 
> transparent to Lua end users, imho.
>
> -ak
I'm not sure I understand what Roberto says in his post but the bytecode 
itself (that is the opcodes) is not the problem. The problem lies in the 
fact that Lua understands only the word 'number', not 'float', 
'integer', 'short' etc. I generally consider this a wise decision but it 
does have drawbacks as in this case. To save space lua would have to 
decide per-number wether this number can be encoded in fewer bits (say 
check wether it is an integer or a real number and how much precision is 
required) and store it accordingly together with some sort of tag saying 
how this number should be interpreted. Not very pretty I know although 
it could be implemented completely transparently to the user. If the 
only objective is to save disk space then this 'number compression' 
could be used only in bytecode stored in files. Once the file is read 
into memory the numbers can be decoded and casted to lua_Number and the 
user will never know the difference. The memory image of the script will 
still be big but the disk file will be smaller. Storing the numbers 
encoded in memory as well would reduce memory space overhead but would 
introduce a lot of decoding and casting time overhead on anything number 
related. Therefore this solution besides introducing quite a bit of 
complexity would propably be completely unacceptable from a performance 
point of view. Even worse hacks could be done by trying to optimize only 
'big' arrays (tables) of numbers instead of single numbers but they 
would propably lead nowhere as well. Still Lua would benefit from a 
solution to this problem. It would be really cool if most apps would 
stop using special-purpose binary or ascii data files, each with its own 
syntax and therefore needing its own parser and using standard scripting 
language files (preferanly lua :)) to do the job.

Dimitris