Re: Why does this work?
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- Subject: Re: Why does this work?
- From: Geoff Leyland <geoff_leyland@...>
- Date: Fri, 4 Feb 2011 16:40:55 +1300
On 4/02/2011, at 4:30 PM, Steve Litt wrote:
> Hi all,
>
> Why does this work?
>
> #!/usr/bin/lua
>
> do
> local oldprint = print
> print = function(str)
> oldprint("======================================")
> oldprint(str)
> oldprint("======================================")
> end
> end
>
> print("Hello World")
> os.exit(0)
>
> I understand everything except the magical working of argument str. How does
> the oldprint(str) between the lines of equal know that the str arg in the
> function declaration refers to the argument of the original print()? Looks
> like magic to me, and I'm going to have to explain it?
Does this help?
local oldprint = print
function newprint(str)
oldprint("======================================")
oldprint(str)
oldprint("======================================")
end
newprint("Hello World")
anyprint = newprint
anyprint("Hello World")
print = newprint
print("Hello World")