Re: array indices in lua

[Mark Feldman <mfeldman@...>]

cynthia powers wrote:
> if I could have everything starting from 0, life would gets a lot 
> easier for me...

You can do it with metatables but the # length operator will no longer 
work properly (overloading the _len operator doesn't work with regular 
tables in the current version of Lua):

function zero_index(t)
  local new_t = {__old_t=t}
  setmetatable(new_t, new_t)
  new_t.__index = function(self, key)
     if tonumber(key) then return self.__old_t[key+1]
     else return self.__old_t[key]
     end
  end
  new_t.__newindex = function(self, key, value)
     if tonumber(key) then self.__old_t[key+1] = value
     else self.__old_t[key] = value
     end
  end
  return new_t
end

t = {"a", "b", "c", foo="bar"}
print(t[1], t[2], t[3], t.foo)      --> a    b    c    bar

t = zero_index(t)
print(t[0], t[1], t[2], t.foo)      --> a    b    c    bar

Mark Feldman


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