Re: 'with' statement

[Dirk Laurie <dirk.laurie@...>]

Thanks to everyone who replied. The present protocol is:

--- with(tbl[,context])
-- Creates a new table with write access to `tbl` and read access to
--   `tbl` and `context`, which defaults to `_ENV`. If current _ENV
--   is local or an upvalue, it must be explicitly given as `context`.
--   If really no context is required, specify an explicit `nil`.
-- Designed for the idiom
--    do local _ENV=with(tbl)
--      ...
--    end
-- which mimics the `with` keyword in Pascal, Visual Basic etc.

The code is:

local
function with(tbl,...)
  local context = ...
  if select('#',...)==0 then context = _ENV end
  if context then
    return setmetatable({},{__newindex=tbl,
      __index=function(_,key) return tbl[key] or context[key] end})
  else
    return tbl
  end
end

2016-03-10 10:09 GMT+02:00 Thijs Schreijer <thijs@thijsschreijer.nl>:
>
>> I never thought I'd say this, but I like the way Visual Basic 6 does it:
>> with foo
>>     .x = 1
>>     .y = some_local_var
>> end with
>> I don't remember the exact syntax, but the important part is you still
>> included the dot from foo.x, so that distinguished properties from other
>> variables in outer scopes.
>
> While reading up the thread, I had the same thought. I also like that about VB.
>
> Thijs