Re: table output

[spir <denis.spir@...>]

Le Tue, 10 Nov 2009 08:11:58 -0600,
hans elbers <hans@hpelbers.org> s'exprima ainsi:

> On Tue, 2009-11-10 at 14:11 +0100, spir wrote:
> Le Tue, 10 Nov 2009 10:35:53 +0000,
> > Duncan Cross <duncan.cross@gmail.com> s'exprima ainsi:
> > > There is no such standard function, and I believe the main reason is
> > > loops - a table might (directly or indirectly) contain fields that
> > > refer to the table itself. For example, the global variable _G is a
> > > reference to the global variables table itself, so if you try to use
> > > your function to display _G then it will get into an infinite loop
> > > trying to display _G._G._G._G...
> >
> > Right.
> >
> > > Now, of course you can rewrite your print function to keep track of
> > > the hierarchy and stop itself when it detects it is about to go into
> > > an infinite loop. But, what do you output instead? It is not trivial
> > > to be concise, meaningful, unambiguous and fit for all purposes here,
> > > as a standard function would have to be.
> >
> > Have no idea how to identify the root table itself (after, I'm a  
> > beginner -- but see also (*)) as we get the object, while nested  
> > ones can be identified while walking, sure.
> > As I said, the output needs not be perfect and a simple placeholder like
> >  <recursion to 'name'> would be fine for me.
> >
> 
> 
> That's exactly what 'print_r' does (I use it for debugging):
> http://www.hpelbers.org/lua/print_r
> 
> It is not intended for serializing, but it's very handy for debugging  
> (or even to see what functions are in a loaded module (just  do pr(_G)  
> and scroll around in the output)
> 
> require 'print_r'
> circle={}
> abcd = {a=1, b=2, c=3, d=4, ref=circle}
> circle['abcd']= '123'
> circle[abcd] = '456'
> circle[print] = 'the standard print function'
> circle['zorro'] = abcd  -- circular reference
> pr(circle, 'my circle'
> 
> This prints:
> 
> my circle = {
> |  function: 0x870a020 = "the standard print function"
> |  zorro = {
> |  |  a = 1
> |  |  c = 3
> |  |  b = 2
> |  |  d = 4
> |  |  ref = {} -- my circle (self reference)
> |  }
> |  table: 0x870e288 = "456"
> |  abcd = "123"
> }

Thank you very much, that's exactly what I had in mind.

Denis
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