Why does “? B” mean “b” in Ruby?

Question

"foo"[0] = ?b # "boo" 

I looked at the example above and tried to figure out:

• How does "? B" mean the character "b"?

• Why is this necessary? - I can’t just write this:

  "foo" [0] = 'b' # "boo"

Answer 1

Ed Swangren :? returns character character code.

Not in Ruby 1.9. Starting from 1.9 ?a returns 'a'. See Here: Son of 10 Things You Need to Know About Ruby 1.9!

 telemachus ~ $ ~/bin/ruby -v ruby 1.9.1p0 (2009-01-30 revision 21907) [i686-linux] telemachus ~ $ ~/bin/ruby -e 'char = ?a; puts char' a telemachus ~ $ /usr/bin/ruby -v ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux] telemachus ~ $ /usr/bin/ruby -e 'char = ?a; puts char' 97 

Edit: A very complete description of the changes in Ruby 1.9 .

Other editing: note that now you can use 'a'.ord if you want the string with the conversion number you get in 1.8 through ?a 'a'.ord

Answer 2

This change is due to Ruby 1.9 UTF-8 updates.

Ruby version 1.8 ? Worked with single-byte characters only. In 1.9, they updated everything to work with multibyte characters. The problem is that it is not clear which integer should return from ?€ .

They solved this by changing what he returns. In 1.9, all of the following are singleton strings and are equivalent:

 ?€ '€' "€" "\u20AC" ?\u20AC 

They were supposed to drop the notation, IMO, and not (somewhat randomly) change the behavior. However, this is not even officially out of date.

Answer 3

? returns the character code of a character. Here is the corresponding article for you.

Answer 4

In some languages ​​(Pascal, Python), characters do not exist: they are just strings of length 1.

In other languages ​​(C, Lisp), characters exist and have clear syntax, for example, 'x' or # \ x.

Ruby was mostly on the "no character" side, but at times it didn't seem to be completely sure about that choice. If you want characters to be a data type, Ruby already assigns the value "and", so what? X looks just as smart as any other option for char literals.

For me, it's just a matter of what you mean. You could also say foo [0] = 98, but you use an integer when you really mean the character. Using a string when you mean a character looks equally strange to me: the set of operations it supports is almost completely different. One of them is the sequence of the other. You would not force Math.sqrt to take a list of numbers and just look only at the first. You would not miss an “integer” from the language just because you already support the “integer list”.

(Actually, Lisp 1.0 did just that - church numbers for everything!), But the performance was terrible, so this was one of the great achievements of Lisp 1.5 that made it suitable for use as a real language, back in 1962. )