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➜ MUSHclient
➜ Lua
➜ Can somebody help me about the string?
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Can somebody help me about the string?
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| Posted by
| Doghell
(3 posts) Bio
|
| Date
| Fri 28 Aug 2009 07:36 AM (UTC) Amended on Fri 28 Aug 2009 07:37 AM (UTC) by Doghell
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| Message
| hello everyone:
i am a beginner of lua. last day i've read a article which mentions that "First, all strings in Lua are internalized;
this means that Lua keeps a single copy of any string. Whenever a new string
appears, Lua checks whether it already has a copy of that string and, if so,
reuses that copy."
[http://www.lua.org/gems/](here is the book).
So yep i just wanna know if i define like this:
>s1 = "hello"
>s2 = "hello"
do s1 and s2 use the same copy? I try to see the address of the two string in the memory, but i don't know how to do it?
(i don't speak english, so excuse me for my poor english,:))
thank you everybody! | | Top |
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| Posted by
| Nick Gammon
Australia (23,173 posts) Bio
Forum Administrator |
| Date
| Reply #1 on Fri 28 Aug 2009 08:09 AM (UTC) |
| Message
| Why do you want to see the addresses? This is an internal thing that you don't need to know in a scripting language.
However I believe that s1 and s2 in your example will refer to the same string.
This make string assignment fast, eg.
s1 = "some very large string"
s2 = s1 -- copy very quickly, as it takes a copy of the pointer to the string
In your case, if you compare s1 and s2 they will compare equal. ie.
s1 = "hello"
s2 = "hello"
print (s1 == s2) -- true
You can also assign functions, eg.
f1 = function () print "hi there" end
f2 = f1
f2 () -- prints: "hi there"
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- Nick Gammon
www.gammon.com.au, www.mushclient.com | | Top |
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| Posted by
| Doghell
(3 posts) Bio
|
| Date
| Reply #2 on Fri 28 Aug 2009 09:15 AM (UTC) |
| Message
|
Nick Gammon said:
Why do you want to see the addresses? This is an internal thing that you don't need to know in a scripting language.
However I believe that s1 and s2 in your example will refer to the same string.
This make string assignment fast, eg.
s1 = "some very large string"
s2 = s1 -- copy very quickly, as it takes a copy of the pointer to the string
In your case, if you compare s1 and s2 they will compare equal. ie.
s1 = "hello"
s2 = "hello"
print (s1 == s2) -- true
You can also assign functions, eg.
f1 = function () print "hi there" end
f2 = f1
f2 () -- prints: "hi there"
Year,thank you very much,Nick.I just wanna test that if these two strings refer to the same string(this is why I'd like to see their addresses).When I define two tables,
t1 = {1,2,3} -- this is a table
t2 = {1,2,3} -- and this is another table
they are two different tables.
Just now I have read some words that prove you are right.
"For strings reuse is not necessary, because Lua
does the job for us: it always internalizes all strings it uses, therefore reusing
them whenever possible. For tables, however, reuse may be quite effective."
And thank you again! :) | | Top |
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