Cipher

I am trying to make a program that takes what you input, and encrypts it
by turning a to p, b to q, z to b, etc. It moves the letter 2 spaces to
the left (a to c) and moves it down (c to p). (See below.) Even though
you can just say that a will be n, how do you seperate each letter and
turn it into a string? Please put it in terms that a Ruby beginner
would understand.
abcdefghijklm
nopqrstuvwxyz

On Mon, Mar 17, 2008 at 1:50 AM, Max Z. [email protected] wrote:

I am trying to make a program that takes what you input, and encrypts it by turning a to p, b to q, z to b, etc. It moves the letter 2 spaces to the left (a to c) and moves it down (c to p). (See below.) Even though you can just say that a will be n, how do you seperate each letter and turn it into a string? Please put it in terms that a Ruby beginner would understand.
abcdefghijklm
nopqrstuvwxyz

You can split a string with the String#split method:
irb

“Foobar”.split(//)
=> [“F”, “o”, “o”, “b”, “a”, “r”]

You can get the ASCII value of a character either with ?character:

?F
=> 70

If you want to loop the splitted string, try eval(has anyone a better
solution?):

“Foobar”.split(//).each { |c| puts eval("?#{c}") }

You can use Fixnum#chr to turn an ASCII value in a character:

65.chr #=> “A”

You’re trying to implement the ROT13 or ROTx algorithm. A naive
approach, still buggy might look like that:
plaintext = “Hello”
encrypted = “”
plaintext.split(//).each { |c| i=eval("?#{c}"); encrypted << (i+13).chr
}
puts encrypted #=> Uryy|

As you see, the encrypted string contains a |(vertical line) and it
also chokes on spaces. I leave the rest to you. Ask again if you’re
stuck.

Regards, Thomas

input = ‘abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
[email protected]#$%^&*()_±={}|[];’:",./<>?~' input.tr! "A-Za-z", "N-ZA-Mn-za-m" => "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM [email protected]\#$%^&*()_+-={}|[]\\;':\",./<>?~"

On Mon, Mar 17, 2008 at 11:16 AM, Thomas W.
[email protected]
wrote:

You can split a string with the String#split method:

“Foobar”.split(//).each { |c| puts eval("?#{c}") }

As you see, the encrypted string contains a |(vertical line) and it
also chokes on spaces. I leave the rest to you. Ask again if you’re
stuck.

Regards, Thomas

“Every child has many wishes. Some include a wallet, two chicks and a
cigar,
but that’s another story.”

On Sun, Mar 16, 2008 at 9:00 PM, Todd B. [email protected]
wrote:

On Sun, Mar 16, 2008 at 7:50 PM, Max Z. [email protected] wrote:

I am trying to make a program that takes what you input, and encrypts it by turning a to p, b to q, z to b, etc. It moves the letter 2 spaces to the left (a to c) and moves it down (c to p). (See below.) Even though you can just say that a will be n, how do you seperate each letter and turn it into a string? Please put it in terms that a Ruby beginner would understand.

Also, I forgot to mention that you should realize that a String object
should be thought of as really just an ordering of bytes with some
special methods to make it human readable.

Todd

On Sun, Mar 16, 2008 at 9:00 PM, Todd B. [email protected]
wrote:

On Sun, Mar 16, 2008 at 7:50 PM, Max Z. [email protected] wrote:

I am trying to make a program that takes what you input, and encrypts it by turning a to p, b to q, z to b, etc. It moves the letter 2 spaces to the left (a to c) and moves it down (c to p). (See below.) Even though you can just say that a will be n, how do you seperate each letter and turn it into a string? Please put it in terms that a Ruby beginner would understand.
abcdefghijklm
nopqrstuvwxyz


Just for fun, I revisited this. To include the printable characters
on an english-based system (ASCII codes 32 through 126), not including
tab, return, line-feed, etc…

puts str = “Hello, world! Yabba dabba doo!”
puts

char_set = (32…126).map.pack(‘c*’)
start, finish, offset = ?a, ?p, ?p - ?a
puts “char_set:\n” + char_set = (?\s…?~).map.pack(‘c*’)
puts

size = char_set.size
new_str = “”
str.each_byte do |byte|
new_str << char_set[(byte + offset - char_set[0]) % size]
end
puts “enciphered: \n” + new_str

Todd

On Sun, Mar 16, 2008 at 7:50 PM, Max Z. [email protected] wrote:

I am trying to make a program that takes what you input, and encrypts it by turning a to p, b to q, z to b, etc. It moves the letter 2 spaces to the left (a to c) and moves it down (c to p). (See below.) Even though you can just say that a will be n, how do you seperate each letter and turn it into a string? Please put it in terms that a Ruby beginner would understand.
abcdefghijklm
nopqrstuvwxyz


Never miss a thing. Make Yahoo your homepage.

There are many ways to do it, but if it was all lower case, I would
probably…

a = “abcdefghijklmnopqrstuvwxyz”
ascii_offset = 15 - 97
str = “antidisestablishmentarianism”
str.each_byte {|b| new_str << a[(b + ascii_offset) % a.size]}
puts new_str

The 15 is to turn a into a p (?p - ?a == 15). The minus 97 part is to
make sure we work in the ascii byte code range. each_byte runs
through each byte of the string, where, in the block, the offset is
added and the mod by the size of a (26) to keep the index of a within
the correct bounds. a[] selects a byte to be appended (<<) to
new_str.

You could wrap this in a method or make it part of String class.
Ideally, I think a person would really want to include the full 256
character set to deal with punctuation and spaces.

Todd

On Sun, Mar 16, 2008 at 9:00 PM, Todd B. [email protected]
wrote:

a = “abcdefghijklmnopqrstuvwxyz”
ascii_offset = 15 - 97
new_str = “”
str = “antidisestablishmentarianism”
str.each_byte {|b| new_str << a[(b + ascii_offset) % a.size]}
puts new_str

I think I’m going to drop google mail; that, or come up with a more
clear way to cut and paste :confused:

Todd

On Mon, Mar 17, 2008 at 5:21 AM, Todd B. [email protected]
wrote:


start, finish, offset = ?a, ?p, ?p - ?a
puts “char_set:\n” + char_set = (?\s…?~).map.pack(‘c*’)
puts

size = char_set.size
new_str = “”
str.each_byte do |byte|
new_str << char_set[(byte + offset - char_set[0]) % size]
end
puts “enciphered: \n” + new_str

Dang it! Another thing that unit tests won’t catch: code that is
redundant! Removing the first “char_set =” line will have the same
result…

puts str = “Hello, world! Yabba dabba doo!”
puts

start, finish, offset = ?a, ?p, ?p - ?a
puts “char_set:\n” + char_set = (?\s…?~).map.pack(‘c*’)
puts

size = char_set.size
new_str = “”
str.each_byte do |byte|
new_str << char_set[(byte + offset - char_set[0]) % size]
end
puts “enciphered: \n” + new_str

Todd

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