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- Subject: Re: Table traversal
- From: Patrick Rapin <toupie300@...>
- Date: Sun, 13 Nov 2011 09:25:45 +0100
> A possibly useful addition to the repertoire of table iterators is
> "traverse", which recursively visits every non-table value in a table
> and returns not that value but a key-table pair (k,s) so that s[k]
> refers to the table entry. This can be extended to allow the cloning
> of table structure and the simultaneous traversal of several tables.
> For example, this is a deep table copy:
> for k,s1,s2 in traverse(t1,t2) do s2[k]=s1[k] end
This is quite an interesting function, for:
- Performing a multiple deep table copy is very easy with the
function, but I think it is rarely needed.
- Comparing two tables with the same structure can be done easily in Lua.
BTW, for both tasks, the few times I have needed that feature, I used
table serialization. .
- To make a deep copy, serialize the first table and evaluate the
string for cloning
- To compare, serialize both tables to files and use a file comparison
But I would also like to use such a function to
- easily dump the table data to screen
- search for a particular data in a recursive table.
In both cases, we need to have *the context* of where the k,s1,s2
values can be found.
The better would be a table with a stack of keys (c in the next example).
So, one could write something like that to compare on screen two tables :
for k,c,s1,s2 in traverse(t1,t2) do
print( table.concat(c,"/"), s1[k], s2[k] )