What's the opposite of chr() in Ruby?
RubyAsciiRuby Problem Overview
In many languages there's a pair of functions, chr() and ord(), which convert between numbers and character values. In some languages, ord() is called asc().
Ruby has Integer#chr, which works great:
>> 65.chr
A
Fair enough. But how do you go the other way?
"A".each_byte do |byte|
puts byte
end
prints:
65
and that's pretty close to what I want. But I'd really rather avoid a loop -- I'm looking for something short enough to be readable when declaring a const.
Ruby Solutions
Solution 1 - Ruby
If String#ord didn't exist in 1.9, it does in 2.0:
"A".ord #=> 65
Solution 2 - Ruby
In Ruby up to and including the 1.8 series, the following will both produce 65 (for ASCII):
puts ?A
'A'[0]
The behavior has changed in Ruby 1.9, both of the above will produce "A" instead. The correct way to do this in Ruby 1.9 is:
'A'[0].ord
Unfortunately, the ord method doesn't exist in Ruby 1.8.
Solution 3 - Ruby
Try:
'A'.unpack('c')
Solution 4 - Ruby
I'd like to +1 dylanfm and AShelly's comment but add the [0]:
'A'.unpack('C')[0]
The unpack call returns an Array containing a single integer, which is not always accepted where an integer is wanted:
$ ruby -e 'printf("0x%02X\n", "A".unpack("C"))'
-e:1:in `printf': can't convert Array into Integer (TypeError)
from -e:1
$ ruby -e 'printf("0x%02X\n", "A".unpack("C")[0])'
0x41
$
I'm trying to write code that works on Ruby 1.8.1, 1.8.7 and 1.9.2.
Edited to pass C to unpack in uppercase, because unpack("c") gives me -1 where ord() gives me 255 (despite running on a platform where C's char is signed).
Solution 5 - Ruby
Just came across this while putting together a pure Ruby version of Stringprep via RFCs.
Beware that chr fails outside [0,255], instead use 1.9.x - 2.1.x portable replacements:
[22] pry(main)> "\u0221".ord.chr
RangeError: 545 out of char range
from (pry):2:in 'chr'
[23] pry(main)> x = "\u0221".unpack('U')[0]
=> 545
[24] pry(main)> [x].pack('U')
=> "ȡ"
[25] pry(main)>
Solution 6 - Ruby
Additionally, if you have the char in a string and you want to decode it without a loop:
puts 'Az'[0]
=> 65
puts 'Az'[1]
=> 122
Solution 7 - Ruby
How about
> puts ?A
Solution 8 - Ruby
You can have these:
65.chr.ord
'a'.ord.chr
Solution 9 - Ruby
If you don't mind pulling the values out of an array, you can use "A".bytes
Solution 10 - Ruby
I'm writing code for 1.8.6 and 1.9.3 and I couldn't get any of these solutions to work in both environments :(
However, I came across another solution: http://smajnr.net/2009/12/ruby-1-8-nomethoderror-undefined-method-ord-for-string.html
That didn't work for me either but I adapted it for my use:
unless "".respond_to?(:ord)
class Fixnum
def ord
return self
end
end
end
Having done that, then the following will work in both environments
'A'[0].ord