I wish to write one method to work with all classes in Digest::Base 
without repeatedly writing the same code.

def setup(file, hash_type)

   # hash_type could be MD5, SHA1, SHA256, etc.

   Digest::hash_type.new
   Hash the file.

end

The above example is what I'd like to be able to do, but it does not 
work. I cannot insert 'hash_type' into the method in this manner. Trying 
to do so produces errors. I can do a bunch of conditionals like this:

def setup(file, hash_type)

   if hash_type == MD5
     Digest::MD5.new
     Hash the file.

   elsif hash_type == RMD160
     Digest::RMD160.new
     Hash the file.

   else....
     ....

end

But then, I begin repeating myself. Any tips on making this work with 
fewer lines of code?

Thanks!