Re: Local Function Forward Declarations

[Rob Hoelz <rob@...>]

On Sat, 29 Sep 2012 15:52:00 -0400
Rena <hyperhacker@gmail.com> wrote:

> On 2012-09-29 3:43 PM, "Mark Gabby" <mwgabby@gmail.com> wrote:
> >
> > Currently, it's possible to forward-declare a local function in Lua
> > like
> so:
> >
> > local forward_declared_function
> >
> > local function calling_function()
> >     print "calling function"
> >     forward_declared_function()
> > end
> >
> > forward_declared_function = function()
> >     print "forward declared function"
> > end
> >
> > This looks kinda ugly, though. I'd like it better if Lua supported
> > this:
> >
> > local forward_declared_function
> >
> > local function calling_function()
> >     print "calling function"
> >     forward_declared_function()
> > end
> >
> > local function forward_declared_function()
> >     print "forward declared function"
> > end
> >
> > With Lua 5.2.1, if you call calling_function() after defining the
> > first,
> it prints:
> > calling function
> > forward declared function
> >
> > but if you call it after the second, it prints, then fails:
> >
> > calling function
> > lua: debug.lua:26: attempt to call upvalue
> > 'forward_declared_function' (a
> nil value)
> > stack traceback:
> >     debug.lua:26: in function 'calling_function'
> >     debug.lua:33: in main chunk
> >     [C]: in ?
> >
> > Why does the first work, but not the second?
> 
> I believe it's because the "local function" statement declares a new
> local variable, shadowing the old one. Code before it is still
> referring to the old one which never gets set.

That's correct.  What Mark is asking for is possible like this:

local forward_declared_function

local function calling_function()
  print 'calling function'
  forward_declared_function()
end

function forward_declared_function()
  print 'forward declared function'
end

That may be a little unclear, though.

-Rob

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