table instances

the underminer · Post by **the underminer** » Mon Jul 24, 2006 4:35 am

They really piss me off, those instances.
When I create the table

Row = &#123;&#125;
block1 = &#123;2,0,1&#125;
Row&#91;1&#93; = block1
Row&#91;2&#93; = block1
Row&#91;1&#93;&#91;1&#93; = 15

then, Row[2][1] becomes 15 too. That's really annoying. Anyone knows a way to avoid this?

be2003 · Post by **be2003** » Mon Jul 24, 2006 9:27 am

idk must be a bug or something.

the underminer · Post by **the underminer** » Mon Jul 24, 2006 9:38 pm

I guess so. I'm sure I didn't make a mistake. It's a real nuisance. Shine, or whoever, can you fix this?

romero126 · Post by **romero126** » Tue Jul 25, 2006 5:08 pm

tostring(block[1])

use that..

the underminer · Post by **the underminer** » Tue Jul 25, 2006 6:04 pm

romero126 wrote:tostring(block[1])

use that..

I think I don't get your hint romero... I changed my code to:

Code: Select all

Row = &#123;&#125;
block1 = &#123;2,0,1&#125;
Row&#91;1&#93; = block1
Row&#91;2&#93; = tostring&#40;block1&#41;
Row&#91;1&#93;&#91;1&#93; = 15 
print&#40;tostring&#40;block1&#41;&#41;
print&#40;Row&#91;2&#93;&#91;1&#93;&#41;

Output =
table: 0x1007eb98
error: source1.lua:7: attempt to index field `?' (a string value)

PeterM · Post by **PeterM** » Tue Jul 25, 2006 6:33 pm

Take this with a huge rock of salt since I'm not a Lua programmer.

Does lua handle non-POD (Plain Old Data) types by reference? If so...

Code: Select all

Row&#91;1&#93; = block1
Row&#91;2&#93; = block1

...would make both rows share the same block1. So you'd have to make a copy somehow.

romero126 · Post by **romero126** » Wed Jul 26, 2006 5:47 am

I used it as a refrence.. not as actual code.
the reason why it has this problem is because its relational variables. Not direct data based variables.

Tables, functions, threads, and (full) userdata values are objects: variables do not actually contain these values, only references to them. Assignment, parameter passing, and function returns always manipulate references to such values; these operations do not imply any kind of copy.

http://www.lua.org/manual/5.0/manual.html#5.4 for more information. learn to research

There are always work arrounds but it still is retarded and half assed. If you really want good code, work with metatables. or Redesign your code so it works logically where all variables are pointers to actual data and not the other way arround.

the underminer · Post by **the underminer** » Wed Jul 26, 2006 4:06 pm

ok i'll read some on metatables since i never used any

Shine · Post by **Shine** » Wed Jul 26, 2006 5:36 pm

the underminer wrote:then, Row[2][1] becomes 15 too. That's really annoying. Anyone knows a way to avoid this?

You can copy the table:

Code: Select all

function copyTable&#40;old&#41;
	local new = &#123;&#125;
	table.foreach&#40;old, function &#40;item&#41; table.insert&#40;new, item&#41; end&#41;
	return new
end

Row = &#123;&#125;
block1 = &#123;2,0,1&#125;
Row&#91;1&#93; = copyTable&#40;block1&#41;
Row&#91;2&#93; = copyTable&#40;block1&#41;
Row&#91;1&#93;&#91;1&#93; = 15

KawaGeo · Post by **KawaGeo** » Thu Jul 27, 2006 2:23 am

table.foreach() function is now deprecated. Use for i,v in ipairs(t) do ..., instead. See Lua 5.1 ref manual.

Code: Select all

function CopyTable&#40;old&#41;
  local new = &#123;&#125;
  -- for i, item in ipairs&#40;old&#41; do table.insert&#40;new, item&#41; end
  for i, item in ipairs&#40;old&#41; do new&#91;i&#93; = item end
  return new
end

the underminer · Post by **the underminer** » Fri Aug 18, 2006 6:29 pm

works like a dream. thnx

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table instances

table instances

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