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- Subject: Re: select("#", ...) idiom
- From: Mark Hamburg <mhamburg@...>
- Date: Wed, 14 Sep 2005 13:34:17 -0700
As discussed recently, another way of getting around this idiom is to add a
standard ieach function which returns index, value for each argument it
receives including nil values.
for i, v in ieach( ... ) do
Fewer copy steps for the values in ...
Allocates a closure and possibly a table
on 9/14/05 1:29 PM, Mark Hamburg at firstname.lastname@example.org wrote:
> Yes, but one could get the length of the first item by writing #(...).
> It seems like #... would be fairly useful assuming the implementation has
> ready access to the length of ...
> That being said, I also understand that this would further complicate the
> grammar since ... wouldn't always be an expression. It would essentially
> require the introduction of a non-terminal for
> on 9/14/05 1:09 PM, Roberto Ierusalimschy at email@example.com wrote:
>>> Perhaps I missed this? What is its meaning?
>> ... is an expression. #exp returns the length of the result of exp.
>> So, #... is the length of the first argument of a vararg function.
>> Try this:
>> function f (...) return #... end
>> print(f("hi", 4, 5))
>> Similarly, <<for i, v in ...>> also has a meaning. See next example:
>> function f (...) for i,v in ... do print(i,v) end end
>> -- Roberto