%!PS-Adobe-2.0 
%
% basic macros --------------------------------------------------------
/BD {bind def} bind def 
/cm   {2.54 div 72 mul} BD
/SL   {setlinewidth} BD
/SRGB {setrgbcolor} BD 
/M    {moveto} BD
/RM   {rmoveto} BD
/L    {lineto} BD
/RL   {rlineto} BD                  
/GS   {gsave } BD
/GR   {grestore} BD
/CPT  {currentpoint T} BD
%
% auxiliary font macros -----------------------------------------------
/E    {exch} BD
/FFSFSF {E findfont E scalefont setfont} BD 
/FTB {/Times-Bold 62 FFSFSF} BD
%
% additional macros ---------------------------------------------------
/TC   {true charpath} BD
/F    {fill} BD
/S    {stroke} BD
/D    {def} BD
/T    {translate} BD
/Sk   {scale} BD
/CP   {closepath} BD
/Ori {0 0 M} BD 
/OrR {Ori rotate} BD 
%
% lut macros ----------------------------------------------------------
/lut2 { [1 0.5 0   1 0.6 0    1 0.75 0   1 0.8 0   1 1 0    0.8 0.9 0
       0.7 0.9 0 0.6 0.9 0    0.5 1 0    0.25 1 0  0 1 0    0 1 0.5
       0 1 1       0 0.7 1    0 0.5 1    0 0.2 1   0 0 1    0.2 0 1
       0.5 0 1     0.7 0 1    1 0 1      1 0 0.5   1 0 0    0 0 0   ] } D
/P2 { 3 mul lut2 exch 3 getinterval aload pop SRGB } BD

%
% peculiar macros -----------------------------------------------------
%  constants
/focus { 6 cm 12.0 cm} BD                                  %focus
4.5  cm /maja E D   3.0 cm /minb E D                       %major minor axes
1 minb minb mul maja maja mul div sub sqrt /ecc E D        %eccentricity
maja minb div minb div /coeff E D                          %C coefficient
1 1 ecc add coeff mul div /r1 E D                          %r1 of periastron
1 1 ecc sub coeff mul div /r2 E D                          %r2 of apoastron

% macro "point of ellipse at theta"
/ellipsept {/theta E D 
            theta cos ecc mul 1 add coeff mul 1 exch div /r E D
            r theta cos mul r theta sin mul} BD
% body -------------------------------------------------------------------------------------

 3.5 cm 5 cm T
 0 setgray
 focus M GS CPT Ori
 0 ellipsept M  0 0.5 360 {ellipsept L} for stroke
 1 0 0 SRGB
 Ori 0 ellipsept L  0 0.5  90 {ellipsept L} for fill
 GR
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