Hash key (?)

ruby-talk
1

Hiya

Im going through the Ruby Cookbook.

On page 51, there is the following example

letter = { ?v => 'aeiou', ?c => 'xyz' }

My question is, what does the key ?v do or mean.

Kind Regards
Brent Clark

2

irb(main):008:0> ?v.class
=> Fixnum
irb(main):009:0> ?v
=> 118
irb(main):010:0> "v"[0]
=> 118

It's a literal that contains the numeric value of the character v

Jesus.

···

On Thu, Jul 29, 2010 at 1:59 PM, Brent Clark <brentgclarklist@gmail.com> wrote:

Hiya

Im going through the Ruby Cookbook.

On page 51, there is the following example

letter = { ?v => 'aeiou', ?c => 'xyz' }

My question is, what does the key ?v do or mean.

3

In earlier versions of Ruby, prefixing a character with a question mark was
sort of a literal for a given character. I just checked irb for 1.8.6 and
1.8.7, ?v would return 118, which is the ascii value of the character v, and
in 1.9.1 it returned "v" the one character String. Another place you can see
this shift take place is in String# where you might say "vat"[0] in 1.8
you would get 118, and in 1.9 you would get "v"

A more idiomatic alternative would probably be to use symbols as hash keys.
letter = { :vowels => 'aeiou' , :consonants => 'xyz' }
(I don't have the book, I'm guessing as to what ?v and ?c are supposed to
mean)

···

On Thu, Jul 29, 2010 at 6:59 AM, Brent Clark <brentgclarklist@gmail.com>wrote:

Hiya

Im going through the Ruby Cookbook.

On page 51, there is the following example

letter = { ?v => 'aeiou', ?c => 'xyz' }

My question is, what does the key ?v do or mean.

Kind Regards
Brent Clark

4

It returns ASCII code following for character question mark:
For example:
irb(main):002:0> ?a
=> 97

···

On 07/29/2010 02:59 PM, Brent Clark wrote:

Hiya

Im going through the Ruby Cookbook.

On page 51, there is the following example

letter = { ?v => 'aeiou', ?c => 'xyz' }

My question is, what does the key ?v do or mean.

Kind Regards
Brent Clark