%!

/A [ 0 1 ] def

A 0 get = % puts A[0] on the stack: 0 

A aload % spills out the contents of A on the stack: 0 1
% PLUS A itself
pop % gets rid of A

A aload pop

A 0 3 put % A now [ 3 1 ] 

% two arguments: 2D array + angle
% returns the array rotated by angle
% functions return values by putting them on the stack
/rotate-2d { 1 dict begin
/B exch def
aload pop 
/y exch def /x exch def
	/c B cos def
	/s B sin def
% [ cx-ys sx+cy ]
[
	c x mul y s mul sub
	s x mul y c mul add
]
end } def

[ 0 1 ] 45 rotate-2d ==