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Grellier, Thierry a écrit : 
So, I would prefer to be able to write something like (VHDL flavor, and
yet another even more disturbing keyword :-) knowing that if elseif...
could be reused)
style = "native"
a = { a = 1,
      b = { b = 2,
            c = 1 when style == "native",
                2 when style == "rock",
                0 else
          }
     }
rather than
[...] 
style = "native"
a = { a = 1,
      b = { b = 2, c = f(style)
          }
     }
function f(style)
...
end

which disseminates the code, and well looks like coding.

In an application I made with Lua, I used functions in tables in a similar way, except that functions were evaluated each time.

a =
{
a = 1,
b =
{
b = 2,
c = function (style)
if style == "native" then return 1
elseif style == "rock" then return 2
else return 0
end
end
}
}
Slightly more verbose than your proposal, but still bearable and using a familiar syntax.

It was a kind of database of city ways, the field indicated which postal area a way belong to. For some ways, it depends on the number of address in the way, eg. odd vs. even, below or above a value, and so on.
When I needed the postal address, I checked the type of the field: if numerical, just use it; if it is a function, evaluate it.
Worked well. No "dissemination". Really nice, showing the flexibility of Lua.

Your need is slightly different as you want to evaluate only once, at construction time. Should I have to do it, I suppose I would walk the table and evaluate the functions I find to fix the values.

I made a typo while writing this code, typing
if style = "native" then

Since assignments are not expressions, I wonder why the == syntax was chosen over the simpler and unambiguous = (beside the familiarity for C users...).

--
Philippe Lhoste
--  (near) Paris -- France
--  http://Phi.Lho.free.fr
--  --  --  --  --  --  --  --  --  --  --  --  --  --