Re: A question on the definition of a chunk

[Sean Conner <sean@...>]

It was thus said that the Great Gavin Wraith once stated:
> In message <20120627184905.GA7463@inf.puc-rio.br> you wrote:
> 
> > > Is this making any sense?
> > 
> > I do not think so. It is the same problem: blocks are lists of
> > statements, but that does not mean that any list of statements is a
> > block. If you draw the syntax tree of the above piece of code, it
> > becomes clear that "x = a()" (in that particular place) is not a
> > block. So, that occurence of "x = a()" cannot be a subblock.
> 
> OK. Reduction is not symmetric :). So, for checking that I have
> it right, am I correct in saying that a local variable's scope 
> consists of the statements or blocks that follow its declaration 
> that also lie within the smallest block that contains its
> declaration? 


Here's two examples of Lua chunks (sans error checking, which would cloud
the issue), compiled via loadstring() (which returns a function that when
run, will execute the code in the given chunk):

	c1 = loadstring [[
		-- this is chunk # 1
		local a	-- this is local to this chunk
		a = 15

		-- this function will be loaded into the default
		-- environment.  In most cases, this will end up
		-- in the global name space.

		function f(x)
		  return 3 * x + a
		end
	]]
	c1()	-- run the loaded chunk

	c2 = loadstring [[
		-- this is chunk #2
		-- this function is local only to this chunk

		local function y(i)
		  return i * a
		end

		-- the 'a' above does not refer to the 'a' defined in the
		-- previous chunk, as that was local to that chunk.  In this
		-- case, y() will default to an 'a' in the global name
		-- space.  If it exists, this will run, otherwise it will
		-- generate an error.

		y(3)
	]]

	-- at this point, c2 is defined, but what happens next ..

	c2()

If 'a' doesn't exist, then running c2() will result in:

[string "                -- this is chunk #2..."]:5: attempt to perform
arithmetic on global 'a' (a nil value)
stack traceback:
        [string "                -- this is chunk #2..."]:5: in function 'y'
        [string "                -- this is chunk #2..."]:14: in function
'c2'
        stdin:1: in main chunk
        [C]: ?

But doing this:

	a = 3
	c2()

yields no errors.

  -spc (Does that help clarify the issue?)