Re: Labeling a tree with MetaObj.

["Denis B. Roegel" <Denis.Roegel@loria.fr>]

On Mon, Jul 02, 2001 at 11:11:07AM +0300, Tarik Kara wrote:
> I would like to draw the tree diagram shown at the attachement with
> MetaObj. I can label the terminal nodes and the edge labeled "o". But I
> had no luck with the nodes label "1", "2", and the other edges. Any
> succestions is appreciated. Thanks in advance.

Below is a solution. I didn't bother to get the same dimensions
as you, though.

I have used the (unfortunately) undocumented treeroot macro, which I should
actually extend a bit.

I know this solution looks complex and that's why a TeX (or ConTeXt) interface
is really needed! :-)

Feel free to post other queries. I'll use them for the next version
of the metaobj manual. However, I am not sure everybody is interested
in this group, so it might be a better idea to post the questions
on the metafont/metapost mailing list, even though I doubt anybody else
than I will answer for some time...

Denis

% Example requested by Tarik Kara.
% A useful inspiration was the figure on page 109 of the metaobj manual.
% D. Roegel, 2 July 2001
input metaobj

setCurveDefaultOption("arrows","draw");
setObjectDefaultOption("Tree")("hideleaves")(true);

def mytc=new_Circle_("")("filled(true)") enddef;

labeloffset:=2bp; % 3bp is the default in plain.mp 

beginfig(1);
  t:=T_(mytc)(mytc,T_(mytc)(mytc,mytc)("hbsep(2cm)"))("hbsep(2cm)");
  Obj(t).c=origin;
  % |ObjLabel| should appear after an object is positionned (this is not
  % clearly stated in the manual); one can always move the object afterwards;
  % this constraint appears when |ObjLabel| is used on subtrees, since
  % |ObjLabel| temporarily attaches the object; when it unties it, links
  % to the embedding object(s) are lost.
  ObjLabel.ntreepos(Obj(t))(1)(btex $(0,2)$ etex) "labcard(s)";
  ObjLabel.ntreepos(Obj(t))(2,1)(btex $(-1,0)$ etex) "labcard(s)";
  ObjLabel.ntreepos(Obj(t))(2,2)(btex $(1,1)$ etex) "labcard(s)";
  % the |treeroot| function should also work for an empty second argument,
  % but this is currently not the case, so one has to use |obj| and |root|
  % in order to dig into the object; it will be corrected in the next version
  % of metaobj.
  ObjLabel.obj(Obj(t)root)(btex $1$ etex) "labcard(n)";
  ObjLabel.treeroot(Obj(t))(2)(btex $2$ etex) "labcard(ne)";
  ObjLabel.Obj(t)(btex $o$ etex) "labpathid(1)", "labdir(lft)";
  ObjLabel.Obj(t)(btex $e$ etex) "labpathid(2)", "labdir(rt)";
  ObjLabel.ntreepos(Obj(t))(2)(btex $f$ etex) "labpathid(1)", "labdir(lft)";
  ObjLabel.ntreepos(Obj(t))(2)(btex $a$ etex) "labpathid(2)", "labdir(rt)";
  draw_Obj(t);
endfig;

end