From: Markus <markus@...>
Date: 2004-09-27T14:39:11+09:00
Subject: Re: {newb} Help with ref

     I will try tell you what I think want you want to know, rather than
what you asked.  If this leaves you with questions, please post again
and I will try again (maybe tomorrow, since it is getting late here).

     First, the easy question.  You can return a value from a function
by writing:

    return x

or, if you let control "fall out the bottom" the last value in the
expression will be returned.  For an example of both forms:

    def factorial(x)
         return 1 if x <= 1
         x*factorial(x-1)
         end

     The more complex problem you are having is not that references are
to "memory locations" but that they are to objects.  It may seem that
these are the same thing (since in both cases you can wind up with a
situation like this:

    s = "test"
    s2 = s
    s[0,1] = "b"

-- and now _both_ strings have changed) but really they are very
different.  In languages like C it is easy to mess with the storage of
something, and even corrupt it, but it is often hard to make a new
thing.  So you wind up often modifying things in place.

     In ruby, it is the other way around: easy to make new things but
harder to modify them.  For example, a somewhat modified version of your
decrypt routine, which is somewhat more in the sprit of ruby might look
like:

WARNING: CODE TYPED DIRECTLY INTO MAIL MESSAGE (UNTESTED)

def decrypt(data,shift = 27)
    if shift < 27 then # if not 27 they know key
        print data.upcase.split(//).collect { |c| 
             i = c[0] - shift
             i += 26 if i < 65
             i.chr
             }.join.downcase,"  	key=",shift,"\n" #plain text lower case
      else 
        for b in 0..25 # loop ever case 
             decrypt(data,b)
             end
      end
    end

The main change is that we upcase the string, split it into characters,
muck with the character's values, join them together, and downcase them
all in one go.

     For an even more rubyesque way to do this, consider something like
this:

WARNING: CODE TYPED DIRECTLY INTO MAIL MESSAGE (UNTESTED)

$letters = ('A'.."Z').to_a.join
def decrypt(data,shift = 27)
    if shift < 27 then # if not 27 they know key
        shifted_letters = $letters[shift..-1]+$letters[0..shift-1]
        print data.upcase.tr($letters,shifted_letters).downcase,"  	key=",shift,"\n" #plain text lower case
      else 
        for b in 0..25 # loop ever case 
             decrypt(data,b)
             end
      end
    end


     Does this help?

          -- Markus



On Sun, 2004-09-26 at 20:56, STEPHEN BECKER I V wrote:
> ########################### code start
> def decrypt(data,shift = 27)
> 	if shift<27 then # if not 27 they know key
> 		datanew=String.new(data.upcase)
> 		a = datanew.size-1 # control loop
> 		while a>-1 
> 			if datanew[a] - shift<65 then #check if it is out of bound of 
> 				datanew[a]=datanew[a]-shift+26#works in my head
> 				else datanew[a]=datanew[a]-shift
> 			end
> 			a-=1
> 		end
> 		print datanew.downcase,"  	key=",shift,"\n" #plain text lower case
> 	else 
> 		for b in 0..25 # loop ever case 
> 			decrypt(data,b)
> 		end
> 	end
> end
> 
> def encrypt(data,shift = rand(26))
> 		
> 		a = data.size-1
> 		while a>-1 
> 			if data[a]+shift>122 then
> 				data[a]=data[a]+shift-26
> 				else data[a]=data[a]+shift
> 			end
> 			a-=1
> 		end
> 		data= data.upcase
> 		print data,"	key=",shift,"\n"
> end
> 
> 
> it=String.new("abcdefghij")
> encrypt(it)
> decrypt(it)
> ############################code end
> it is the wonderful ceaser shift, you add or subtract a key to the char.
> Anyway, I am lost on why i have to create a copy of the string in
> decrypt. I know why my it string gets crushed because encrypt uses it.
> How does one make it use a copy of the varablie instead of pointing to
> the memory location? also how do you return a value in a
> function(def)? If you do not want to tell me because you dont think i
> read the chm file, then please tell me where i can read how to do this
> (simple examples would also be great)?
> Thank you for your time.
> Stephen Becker