How do I increment/decrement a character in Ruby for all possible values?

Question

I have a string that is one character long and can be any possible character value:

irb(main):001:0> \"\\x0\"
=> \"\\u0000\"

I though

Answer 1

You cannot do:

"\x0" += 1

Because, in Ruby, that is short for:

"\x0" = "\x0" + 1

and it is a syntax error to assign a value to a string literal.

However, given an integer n, you can convert it to a character by using pack. For example,

[97].pack 'U' # => "a"

Similarly, you can convert a character into an integer by using ord. For example:

[300].pack('U').ord # => 300

With these methods, you can easily write your own increment function, as follows:

def step(c, delta=1)
  [c.ord + delta].pack 'U'
end

def increment(c)
  step c, 1
end

def decrement(c)
  step c, -1
end

If you just want to manipulate bytes, you can use String#bytes, which will give you an array of integers to play with. You can use Array#pack to convert those bytes back to a String. (Refer to documentation for encoding options.)