[metapost] fullcircle in metapost language

[Pierre Lorenzon]

Hi,

Excuse me if this question already occured many times on the
list but I am an occasional metapost user and did not know the
existence of this list before today.

Following metapost code :

beginfig(1);
  %tracingall;
  pair A,B,C,I,Ap,Bp,Cp,As,Bs,Cs; %les points de la figure
  path Da,Db,Dc; %les bissectrices intérieures
  numeric alpha,beta,gamma; %les longueurs des côtés
  A=(0,0);
  B=(6cm,0);
  C=(2cm,6cm);

  %Calcul des longueurs
  a=abs(B-C);
  b=abs(C-A);
  g=abs(A-B);
  (a+b+g)*alpha = a;
  (a+b+g)*beta = b;
  (a+b+g)*gamma = g;

  %Les points A',B',C'
  beta*(B-Ap) + gamma*(C-Ap) = (0,0);
  gamma*(C-Bp) + alpha*(A-Bp) = (0,0);
  alpha*(A-Cp) + beta*(B-Cp) = (0,0);

  %Les bissectrices
  Da = A--Ap;
  Db = B--Bp;
  Dc = C--Cp;

  %Le centre du cercle circonscrit
  alpha*(A-I) + beta*(B-I) + gamma*(C-I) = (0,0);

  %Les projetés de I
  (As-I) rotated 90 = whatever*(C-B);
  (As-B) = whatever*(C-B);
  (Bs-I) rotated 90 = whatever*(A-C);
  (Bs-C) = whatever*(A-C);
  (Cs-I) rotated 90 = whatever*(B-A);
  (Cs-A) = whatever*(B-A);

  %Le cercle inscrit
  path cercle;
  cercle = fullcircle scaled 2*abs(As-I) shifted I;

  %Tracé de la figure
  draw Da;
  draw Db;
  draw Dc;
  draw cercle;
  dotlabel.bot(btex $I$ etex,I);
  dotlabel.lft(btex $A$ etex,A);
  dotlabel.rt(btex $B$ etex,B);
  dotlabel.top(btex $C$ etex,C);
  dotlabel.rt(btex $A'$ etex,Ap);
  dotlabel.lft(btex $B'$ etex,Bp);
  dotlabel.bot(btex $C'$ etex,Cp);
  dotlabel.rt(btex $A''$ etex,As);
  dotlabel.lft(btex $B''$ etex,Bs);
  dotlabel.bot(btex $C''$ etex,Cs);

  %Le triangle
  draw A--B--C--cycle;
endfig;

compiled perfectly a few years ago with metapost 0.64 in web2C
7.3.1. 

Today metapost version is 
MetaPost 0.641 (Web2C 7.5.4)
kpathsea version 3.5.4
Copyright (C) 1997-2004 AT&T Bell Laboratories.
Kpathsea is copyright (C) 1997-2004 Free Software Foundation, Inc.
There is NO warranty.  Redistribution of this software is
covered by the terms of both the MetaPost copyright and
the GNU General Public License.
For more information about these matters, see the files
named COPYING and the MetaPost source.
Primary author of MetaPost: John Hobby.
Kpathsea written by Karl Berry and others.

corresponding to installation of tetex 3.0 and I recieve
following error message :

This is MetaPost, Version 0.641 (Web2C 7.5.4) (mem=mpost 2005.10.11)  19 OCT 2007 13:46
**C-Bissectrices.mp
(C-Bissectrices.mp
>> path
>> 52.23541
! Not implemented: (path)*(known numeric).
<to be read again> 
                   shifted
l.43 ...le = fullcircle scaled 2*abs(As-I) shifted
                                                   I;
? 
! Emergency stop.
<to be read again> 
                   shifted
l.43 ...le = fullcircle scaled 2*abs(As-I) shifted
                                                   I;
End of file on the terminal!


as if the circle could not be scaled and shifted ! Why ? Did
something change in language specification ? I can not believe
it ! Is some ressource not available for any environment reason
? 

Regards

Pierre