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- Subject: Re: Redefining locals
- From: Mark Hamburg <mhamburg@...>
- Date: Thu, 11 Nov 2004 08:54:57 -0800
on 11/11/04 8:30 AM, Roberto Ierusalimschy at firstname.lastname@example.org wrote:
> They capture the variables, not their values. The foo in that function
> is not free at all, it is forever binded to the local variable created
> with the first "local" declaration.
Which leaves the question that started this thread: Is it useful to be able
to capture a variable and then create a new variable with the same name in
what appears to be the same scope? (Arguably each local declaration creates
a new invisible scope that extends to the end of the visible scope.)
I can see a variety of levels of prohibition:
1. None -- i.e., what Lua has now. Creating a new local is always allowed.
2. Prohibit creating locals in the same block with the same name. Thus, the
following is illegal:
But the following is legal:
3. Prohibit creating locals that hide any existing locals. This rules out
the second example above.
In C, I've sometimes wished for 3, since the errors can be subtle, but I can
go either way on whether it's allowed or disallowed.
It's the second case that has bitten me a few times when I've written:
local foo -- forward declaration
local function baz() foo() end
local function foo()
if bar() then baz() end
The second declaration of foo does not fill in the forward declaration.