From: "Peña, Botp" <botp@...>
Date: 2008-06-19T11:07:09+09:00
Subject: Re: How to capture a keypress

From: cowkiller123@gmail.com [mailto:cowkiller123@gmail.com] 
#...
# I just don't understand one thing from the code above: the 
# "?\C-x", in the when statement. 

if you studied the code, you can deduce that it's a literal character for the keyboard combination Control-x. In ruby, single characters can be represented by prefixing the ? to the char but without the usual quoting.


There are some caveats however, and the best way to learn/test is using irb, eg

RUBY_VERSION
#=> "1.8.6"

?\C-x
#=> 24

so in ruby1.8.6, the single char evaluates to an integer, wc if you look closely, is the ascii code. again, note, it's an integer.

?\C-x.class
#=> Fixnum

of course you can represent single chars as a string,

"\C-x"
#=> "\030"

oops, you'll have to evaluate that further to get to the ? behaviour

030
#=> 24

ergo, you cannot compare ?-ied chars with quoted chars directly.

?\C-x == "\C-x"
#=> false

again,

?a
#=> 97

"a"
#=> "a"

?a == "a"
#=> false

:)

also, judging fr the above, you cannot represent multi-byte chars using the ? in ruby 1.8.6.


In ruby1.9 however, it's much better and more natural. the way it should be, so to speak.

?\C-x
=> "\x18"

"\C-x"
=> "\x18"

?a
=> "a"

"a"
=> "a"

?a == "a"
=> true

Ergo, in ruby1.9, you may not need the ? single char representation, the usual quoting may do.

kind regards -botp