Re: native code for bitwise operators in LUA

[HyperHacker <hyperhacker@...>]

On Thu, Nov 3, 2011 at 20:55, Xavier Wang <weasley.wx@gmail.com> wrote:
> 2011/11/4 HyperHacker <hyperhacker@gmail.com>:
>> On Thu, Nov 3, 2011 at 18:31, Luiz Henrique de Figueiredo
>> <lhf@tecgraf.puc-rio.br> wrote:
>>>> Trying to port it to using the bit library is very error-prone
>>>
>>> Perhaps there is a niche for a tool that converts infix bitwise
>>> expressions in whatever syntax you prefer to Lua code using the bit
>>> library. It's probably quite easy to write this tool with LPEG.
>>>
>>>
>>
>> I've thought about doing similar: a function that just parses a string
>> like "x << (y | z)" and interprets it at runtime. Your idea though has
>> the advantage that you don't have to do any variable interpolation and
>> the parsing only needs to be done once.
>>
>> --
>> Sent from my toaster.
>>
>>
>
> It's very easy with metalua[1], see below:
>
> -{block:
>    mlp.expr.infix:add { '&', prec = 35, builder = |a,_,b| +{
> bit.band(-{a}, -{b}) } }
>    mlp.expr.infix:add { '|', prec = 36, builder = |a,_,b| +{
> bit.bor(-{a}, -{b}) } }
>    mlp.expr.prefix:add { '!', prec = 80, builder = |_,a| +{ bit.bnot(-{a}) } }
> }
>
>
> require 'bit'
>
> print( 0xF0 & 0xAA )
>
>
> you can product bytecode file with metalua, without parse it runtime.
>
> [1]: http://metalua.luaforge.net/
>
>

Interesing. But then I'd have to learn metalua...

-- 
Sent from my toaster.