Re: help to (slightly) modify Lua interpreter

[Mark Feldman <mfeldman@...>]

Francesco Abbate wrote:
> I'm planning to translate the code like that:
>
> m[i, j]         => __index(m, i, j)
> m[i, j] = v    => __newindex(m, i, j, v)
>
> So all the indexes will be feeded to the __index or __newindex
> metamethods in the order.

Can you wrap the indices into their own seperate table, i.e. m[{1,2}]? 
The code below uses only a single __index/__newindex handler but it 
works for an arbitrary number of dimensions and could be modified to 
pass control down through the heirarchy.

Mark Feldman


mt =
{
   __index = function(table, indices)
       if tonumber(indices) then
           return rawget(table, indices)
       else
           for i=1,#indices-1 do
               table = table[indices[i]]
           end
           return table[indices[#indices]]
       end
   end,
   
   __newindex = function(table, indices, value)
       if tonumber(indices) then
           rawset(table, indices, value)
       else
           for i=1,#indices-1 do
               table = table[indices[i]]
           end
           table[indices[#indices]] = value
       end
   end,
}

m = {}
setmetatable(m, mt)

m[{1}] = {}
m[{2}] = {}
print(m[{1}])       --> table: 00463F48
print(m[{2}])       --> table: 00463FF8
m[{1,2}] = "foo"
print(m[{1,2}])    --> foo

m[{3}] = {}
m[{3,4}] = {}
m[{3,4,5}] = "bar"
print(m[{3,4,5}])  --> bar


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