%!PS
% Joseph O'Rourke
% Illustrates a procedure with parameters

3 setlinewidth

% How to call: xmin ymin length square
/square {
   /x exch def % Store square side length into variable x
   moveto % move to lowerleft corner (xmin,ymin) on stack top
   % Use relative moves below to draw four sides:
   x 0 rlineto
   0 x rlineto
   x neg 0 rlineto % NB!: need to neg x, because -x is illegal
   % Could now say: 0 x neg rlineto; but use closepath instead
   closepath
   stroke
} def

1 0 0 setrgbcolor
100 500 100 square

0 1 0 setrgbcolor
300 400 50 square

0 0 1 setrgbcolor
50 50 375 square



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