I've found it weird that String#hex in Ruby doesn't return the right hex value for a given char. I might be misunderstanding the method, but take the following example:
'a'.hex
=> 10
Whereas the right hex value for 'a' would be 61:
'a'.unpack('H*')
=> 61
Am I missing something? What's hex for? Any hints appreciated!
Thanks
In Ruby, string is a sequence of one or more characters. It may consist of numbers, letters, or symbols. Here strings are the objects, and apart from other languages, strings are mutable, i.e. strings can be changed in place instead of creating new strings.
Strings exist within either single quotes ' or double quotes " in Ruby, so to create a string, enclose a sequence of characters in one or the other: 'This is a string in single quotes. ' "This is a string in double quotes." You can choose to use either single quotes or double quotes.
A string in Ruby is an object (like most things in Ruby). You can create a string with either String::new or as literal (i.e. with the double quotes "" ). But you can also create string with the special %() syntax With the percent sign syntax, the delimiters can be any special character.
String#hex
doesn't give you the ASCII index of a character, it's for transforming a base-16 number (hexadecimal) from a string to an integer:
% ri String\#hex
String#hex
(from ruby site)
------------------------------------------------------------------------------
str.hex -> integer
------------------------------------------------------------------------------
Treats leading characters from str as a string of hexadecimal digits
(with an optional sign and an optional 0x) and returns the
corresponding number. Zero is returned on error.
"0x0a".hex #=> 10
"-1234".hex #=> -4660
"0".hex #=> 0
"wombat".hex #=> 0
So it uses the normal mapping:
'0'.hex #=> 0
'1'.hex #=> 1
...
'9'.hex #=> 9
'a'.hex #=> 10 == 0xA
'b'.hex #=> 11
...
'f'.hex #=> 15 == 0xF == 0x0F
'10'.hex #=> 16 == 0x10
'11'.hex #=> 17 == 0x11
...
'ff'.hex #=> 255 == 0xFF
It's very similar to String#to_i
when using base 16:
'0xff'.to_i(16) #=> 255
'FF'.to_i(16) #=> 255
'-FF'.to_i(16) #=> -255
From the docs:
% ri String\#to_i
String#to_i
(from ruby site)
------------------------------------------------------------------------------
str.to_i(base=10) -> integer
------------------------------------------------------------------------------
Returns the result of interpreting leading characters in str as an
integer base base (between 2 and 36). Extraneous characters past the
end of a valid number are ignored. If there is not a valid number at the start
of str, 0 is returned. This method never raises an exception
when base is valid.
"12345".to_i #=> 12345
"99 red balloons".to_i #=> 99
"0a".to_i #=> 0
"0a".to_i(16) #=> 10
"hello".to_i #=> 0
"1100101".to_i(2) #=> 101
"1100101".to_i(8) #=> 294977
"1100101".to_i(10) #=> 1100101
"1100101".to_i(16) #=> 17826049
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