about table operation in lua-ConTeXt

about table operation in lua-ConTeXt

[Jeong Dal]

Dear all,

It may be a slight off topic.
In the following example, I copied a table “m” to “tempM”, and remove the last row of tempM.
Then the output is “ 2, 2”
I checked the contents of tempM and m and found that they are same even though I didn’t touch m.
I want to remove the last row of tempM while keeping the table m untouched.
Please tell me how to do it.

Thank you.
Best regards,

Dalyoung

\startbuffer[test]
\startluacode
 m = {{0, 2, 4},{2, 3 , 4}, {2, 2, -6}}
local tempM = {}

tempM = m
table.remove(tempM)
context(#tempM, “, ” , #m)
\stopluacode
\stopbuffer

\starttext
getbuffer[test]
\stoptext



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Re: about table operation in lua-ConTeXt

[Henri Menke]

On 02/13/2017 06:50 AM, Jeong Dal wrote:
> Dear all,
> 
> It may be a slight off topic.
> In the following example, I copied a table “m” to “tempM”, and remove the last row of tempM.
> Then the output is “ 2, 2”
> I checked the contents of tempM and m and found that they are same even though I didn’t touch m.
> I want to remove the last row of tempM while keeping the table m untouched.
> Please tell me how to do it.
> 
> Thank you.
> Best regards,
> 
> Dalyoung
> 
> \startbuffer[test]
> \startluacode
>  m = {{0, 2, 4},{2, 3 , 4}, {2, 2, -6}}
> local tempM = {}
> 
> tempM = m

Do a deep copy
tempM = table.copy(m)

> table.remove(tempM)
> context(#tempM, “, ” , #m)
> \stopluacode
> \stopbuffer
> 
> \starttext
> getbuffer[test]
> \stoptext
> 
> 
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
> 

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___________________________________________________________________________________

Re: about table operation in lua-ConTeXt

[Hans Hagen]

On 2/13/2017 6:50 AM, Jeong Dal wrote:
> Dear all,
>
> It may be a slight off topic.
> In the following example, I copied a table “m” to “tempM”, and remove the last row of tempM.
> Then the output is “ 2, 2”
> I checked the contents of tempM and m and found that they are same even though I didn’t touch m.
> I want to remove the last row of tempM while keeping the table m untouched.
> Please tell me how to do it.

\startbuffer[test]
\startluacode
     local t1 = {{0, 2, 4},{2, 3 , 4}, {2, 2, -6}}
     local t2 = t1 -- t2 points to t1
     local t3 = table.copy(t1)

     table.remove(t3)

     context.tocontext(t1)
     context.tocontext(t2)
     context.tocontext(t3)

\stopluacode
\stopbuffer

\starttext
\getbuffer[test]
\stoptext



> Thank you.
> Best regards,
>
> Dalyoung
>
> \startbuffer[test]
> \startluacode
>  m = {{0, 2, 4},{2, 3 , 4}, {2, 2, -6}}
> local tempM = {}
>
> tempM = m
> table.remove(tempM)
> context(#tempM, “, ” , #m)
> \stopluacode
> \stopbuffer
>
> \starttext
> getbuffer[test]
> \stoptext
>
>
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
>
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
>


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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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___________________________________________________________________________________

Re: about table operation in lua-ConTeXt

[Procházka Lukáš Ing.]

Hello,

tables in Lua are "shared" - there is one copy until you "deep copy" one to another.

Se  comments bellow -

On Mon, 13 Feb 2017 06:50:38 +0100, Jeong Dal <haksan@me.com> wrote:

> Dear all,
>
> It may be a slight off topic.
> In the following example, I copied a table “m” to “tempM”, and remove the last row of tempM.
> Then the output is “ 2, 2”
> I checked the contents of tempM and m and found that they are same even though I didn’t touch m.
> I want to remove the last row of tempM while keeping the table m untouched.
> Please tell me how to do it.
>
> Thank you.
> Best regards,
>
> Dalyoung
>
> \startbuffer[test]
> \startluacode
>  m = {{0, 2, 4},{2, 3 , 4}, {2, 2, -6}}
> local tempM = {} -- OK, 'tempM' and 'm' are different tables - try 'print(tempM, m)' - you'll get two addresses
>
> tempM = m -- Now, 'tempM' and 'm' will point to the same table - "the 'm' table"
-- The original 'tempM' table will be forgotten and removed during next garbage collection as there is no other reference to it
-- ('tempM' starts pointing to 'm', too)
> table.remove(tempM) -- Will remove from one
> context(#tempM, “, ” , #m) -- Obviously - both table point to the same object, try again 'print(tempM, m)'
> \stopluacode
> \stopbuffer
>
> \starttext
> getbuffer[test]
> \stoptext

Best regards,

Lukas


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___________________________________________________________________________________

Re: about table operation in lua-ConTeXt

[Jeong Dal]

Dear Henri, Hans, Procházka,

Thank you for the answers.
It is what I want, and I can complete my code.

Thanks again.
Best regards,

Dalyoung

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