Re: debugging/logging question

[Duncan Cross <duncan.cross@...>]

On Thu, Oct 8, 2009 at 11:20 PM, Norbert Kiesel <nkiesel@tbdnetworks.com> wrote:
> Hi,
>
> is it possible to get the name of a variable within Lua if I only have
> the variable?  I want to write a small helper function logger that
> basically prints the name and the value of the variable
>
> function logger(name, value) print(name, 'has value', value) end
> foo = 'hello'
> logger('foo', foo)
>
> Now I'd like to just call "logger(foo)" and get the same output.

I don't think there is any way for logger() to determine that - all it
has is the evaluated value of foo, not some reference to the token
'foo'.

If you don't mind it being logger('foo') instead of logger(foo), that's doable:

do

  function logger(varname)
    local i = 1
    while true do
      local lname,lvalue = debug.getlocal(2,i)
      if (lname == varname) then
        print(lname, "has value", lvalue)
        break
      elseif (lname == nil) then
        print(varname, "has value", _G[varname])
        break
      end
      i = i + 1
    end
  end

  globalvar = 10
  function test()
    local localvar = 5
    logger('localvar')
    logger('globalvar')
  end

  test()

end

...though as it is that will only work for local variables inside
test(), not "outer" locals.

-Duncan