POSTSCRIPT EXERCISES

READING 
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Notes for lecture 7.
Sedgewick, p. 141

SUPPLEMENTAL READING
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See course FAQ page

EXERCISES
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For Questions 1-5, assume that the stack is initially empty, and give the
contents of the stack after the given PostScript program is executed.

 1. 
       1 dup add dup add dup add dup add

 2.
       1 dup mul dup mul dup mul dup mul

 3.
       2 dup mul dup mul dup mul dup mul

 4.
       1 1 2 copy add 2 copy add 2 copy add 2 copy add

    [Note: "copy" pops an integer N off the stack, then
     copies the N integers at the top of the stack. "1 copy"
     is the same as "dup".]

 5.
       1 1 10 { 2 copy add } repeat

    [Note: "N {...} repeat" executes the grouped sequence N times.]

 6. What does the following Postscript program do?

       %!
       200 200 moveto 
       100 100 rlineto 
       200 300 moveto 
       100 -100 rlineto
       stroke showpage

 7. What does the following Postscript program do?

       %!
       100 -100 200 300 100 100 200 200
       moveto rlineto moveto rlineto
       stroke showpage

 8. What does the following Postscript program do?

       %!
       200 200 moveto 300 300 lineto 200 300 moveto 300 200 lineto
       stroke showpage

 9. Write a Postscript program to draw a "T".

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		    ANSWERS TO POSTSCIPT EXERCISES 

 1. 16

 2. 1

 3. 65536  (A few more "dup mul" operations would caluculate some truly
    huge integers: PostScript eventually represents them as "infinity"
    rather than overflowing.)

 4.    1   1   2   3   5   8  (Fibonacci numbers.)

 5.    1   1   2   3   5   8   13   21   34   55   89   144

 6. Draws an "X".

 7. Same thing.
 
 8. Same thing.
 
 9. 
       %!
       200 200 moveto 
       0 100 rlineto 
       150 300 moveto 
       100 0 rlineto
       stroke showpage