Re: [Celestia-developers] More scripting changes

[Fridger S. <t0...@ma...>]

Chris Laurel wrote:
> 
> On Tue, 15 Apr 2003, Christophe Teyssier wrote:
> 
> >
> > I've added a celestia:getchilds(object) which returns a table of all the
> > childs of object, and here is a script that visits the entire solar system
> > :-)
> >
> > function goto(o, t)
> >     local obs = celestia:getobserver()
> >     obs:goto(o, t)
> >         while (obs:travelling()) do
> >         wait(0)
> >     end
> > end
> >
> > function visit(o)
> >     local i, v
> >     celestia:select(o)
> >     goto(o, 3)
> >     wait(0.5)
> >     local childs = celestia:getchilds(o)
> >     for i, v in ipairs(childs) do
> >         visit(v)
> >     end
> > end
> >
> > sol = celestia:find("Sol")
> > visit(sol)
> 
> Very nice!
> 
> Lua seems to be close to the optimal embedded scripting language.  Small,
> free, fast, portable, easily extensible, with powerful constructions like
> closures and coroutines . . .  One thing that /does/ appear to be missing
> is a way to write iterators.  With an iterator, instead of actually
> filling a table with values, you could define a next function to produce
> the next value in the sequence.  This is especially useful for the stars
> database, where you definitely do not want to generate a Lua object for
> every single star.
> 

But I guess you know that (circular) linked lists are included:

      list = {}                    -- creates an empty table
      current = list
      i = 0
      while i < 10 do
        current.value = i
        current.next = {}
        current = current.next
        i = i+1
      end
      current.value = i
      current.next = list

or also

      colors = {}
      colors[1] = "blue";  colors[2] = "yellow"; colors[3] = "red"
      colors[4] = "green"; colors[5] = "black"

being equivalent to
      
      colors = {"blue", "yellow", "red", "green", "black"}


Finally, the ability to traverse tables, using the built-in function 'next',
like so:

    function clone (o)
     local new_o = {}           -- creates a new object
     local i, v = next(o,nil)   -- get first index of "o" and its value
     while i do
       new_o[i] = v             -- store them in new table
       i, v = next(o,i)         -- get next index and its value
     end
     return new_o
   end



Bye Fridger