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于 2012-7-19 9:31, Luiz Henrique de Figueiredo 写道:
Do you really want to write tostring() without arguments? What for?

It is more as a failsafe for this kind of scenario:

    table.concat{stuff, tostring(foo()), ... }

where foo is dynamic and may return nothing.
In this case, if you know you have to protect yourself, use
	table.concat{stuff, tostring((foo())), ... }
Note the extra pair of parentheses around foo().

whow, I didn't realize that the parentheses can `increase' the number of values in a explist.
I thought it could only `reduce' it.

shame on me.

I have read the manual, and found the manual said,
>In all other contexts, Lua adjusts the result list to one element, discarding all values except the first one.
I am thinking it might be better saying
   " one element, either discarding all values except the first one if the explist is non-empty, or giving a single `nil' value otherwise."