RE: manipulating data
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- Subject: RE: manipulating data
- From: "Jerome Vuarand" <jerome.vuarand@...>
- Date: Mon, 5 Feb 2007 13:01:37 -0500
Darius Blaszijk wrote:
> I understand what you mean. The problem however is that I
> don't want to store the same data as table in the lua state
> and in my application as object (for memory and debugging
> reasons). Therefore I was thinking of using a getter and
> setter function that encapsulates the data. So in effect:
>
> data[1,2] = 1.234 is comparable in calling the function
> setdata(1,2,1.234) and print(data[1,2] is comparable to
> calling the function getdata(1,2)
>
> the first does not return any value, the second returns the
> value of the data object in my app at position 1,2
You can use the slightly more complex syntax data[{1, 2}]. To do that
youmust use index and newindex metamethods. Here is an example with
tables:
function matrix()
local self = setmetatable({}, {
matrix = {},
__newindex = function(self, key, value)
local t = getmetatable(self).matrix
for i=1,#key-1 do
if not t[key[i]] then t[key[i]] = {} end
t = t[key[i]]
end
t[key[#key]] = value
end;
__index = function(self, key)
local t = getmetatable(self).matrix
for i=1,#key-1 do
if not t[key[i]] then t[key[i]] = {} end
t = t[key[i]]
end
return t[key[#key]]
end;
})
return self
end
local m = matrix(2)
m[{1,2}] = 1.234
print(m[{1,2}])
print(m[{3,2}])
print(m[{1,4}])
You may have to complete this example to deal with the cases where given
indices don't match your matrix dimension.