%!

% set units to inches
72 dup scale
1 72 div setlinewidth

2 2 translate

% draw some axes
0.7 setgray
newpath
-1 0 moveto
2 0 lineto
0 -1 moveto
0 2 lineto
stroke

0 setgray

% x is the only argument for f = x^2
/f { 1 dict begin 	% magic
% the "1" here is the number of definition s made within this procedure
/x exch def % 
% x is now the single argument to the function
x x mul
% the line above is the only one specific to this fumnction
end   			% magic
} def

% the graph will be made up of N line segments
/N 100 def

/x0 0 def % initial x
/xf 1 def % final x

/x x0 def
/dx xf x0 sub N div def

newpath
x x f moveto
% start at the initial value of (x, y)
N {
/x x dx add def
% update x
x x f lineto
} repeat
stroke

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