For the first homework assignment, you'll be warming up to Ruby. The due date is Wednesday, September 17 for graduates and Thursday, September 18 for undergraduates.

Readings: Read as many on-line tutorials or book chapters on Ruby as is reasonable without seriously impacting your personal life.

1. Write a Ruby script (in the file prefixes.rb) that writes successive prefixes of its first input argument, one per line, starting with the first prefix, which is zero characters long. For example:

   $ ruby prefixes.rb matsumoto
   
   m
   ma
   mat
   mats
   matsu
   matsum
   matsumo
   matsumot
   matsumoto
   

2. Write a ruby script (in the file lines.rb) that reports the number of lines in the file named by the first argument. For example, if the file states.txt has 50 lines:

   $ ruby lines.rb states.txt
   50
   

3. Write a Ruby method that takes in a string s and returns the string which is equivalent to s but with all ASCII vowels removed. For example, in irb:

   >> strip_vowels("Hello, world")
   => "Hll, wrld"
   

4. Write a Ruby method that randomly permutes a string. By random we mean that each time you call the method for a given argument all possible permutations are equally likely (note that "random" is not the same as "arbitrary.") For example, in irb:

   >> scramble("Hello, world")
   => "w,dlroH elol"
   

5. Write a Ruby generator method that yields powers of two starting at 1 and going up to some limit. For example, in irb:

   >> powers_of_two(70) {|x| puts x}
   1
   2
   4
   8
   16
   32
   64
   => nil
   

6. Write a Ruby generator method that yields powers of an arbitrary base starting at exponent 0 and going up to some limit. For example, in irb:

   >> powers(3, 400) {|x| puts x}
   1
   3
   9
   27
   81
   243
   => nil
   

7. Write a method that interleaves two arrays. If the arrays do not have the same length, the elements of the longer array should end up at the end of the result array. For example, in irb:

>> interleave(["a", "b"], [1, 2, true, nil])
=> ["a", 1, "b", 2, true, nil]

8. Write a method that doubles up each item in an array. For example, in irb:

   >> [5,4,[3],9].stutter
   => [5,5,4,4,[3],[3],9,9]