Re: do some operation on a set of values

[Peyman <peiman_3009@...>]

--- On Sat, 12/25/10, Duncan Cross <duncan.cross@gmail.com> wrote:

> From: Duncan Cross <duncan.cross@gmail.com>
> Subject: Re: do some operation on a set of values
> To: "Lua mailing list" <lua-l@lists.lua.org>
> Date: Saturday, December 25, 2010, 8:52 PM
> 
>  -- create a new metatable
>  meta = {}
> 
>  -- define a function that returns a table after giving it
> our metatable
>  function valueset(t)
>    return setmetatable(t or {}, meta)
>  end
> 
>  -- add metamethods to our metatable that change behavior
> for + and *
>  function meta.__add(set1, set2)
>    local result = {}
>    for i = 1, math.min(#set1, #set2) do
>      result[i] = set1[i] + set2[i]
>    end
>    return valueset(result)
>  end
>  function meta.__mul(set1, set2)
>    local result = {}
>    for i = 1, math.min(#set1, #set2) do
>      result[i] = set1[i] * set2[i]
>    end
>    return valueset(result)
>  end
> 
>  -- test it
>  a = valueset{1, 2, 3}
>  b = valueset{5, 6, 7}
> 
>  c = a + b             
>   --> {6, 8, 10}
>  c = a * b             
>   --> {5, 12, 21}
> 
> 
> -Duncan
> 

thanks Duncan very very useful, i read Metamethods Tutorial in lua wiki and find out metatable is very interesting and amazing.
i think simple example like these must be in the lua manual in future but anyway thanks again.
Peyman.