&. in Ruby 2.3.0

ruby-talk
1

Hi
Why do I get an error (ruby 2.3.0)?
[1,2,3]&.upcase
What am I doing wrong here?
(I know there is no Array.upcase)

Thanks
Berg

2

What are you trying to do? The error message seems clear enough:

irb(main):002:0> [1,2,3]&.upcase
NoMethodError: undefined method `upcase' for [1, 2, 3]:Array
from (irb):2

···

On Sat, Apr 2, 2016 at 5:01 PM, A Berger <aberger7890@gmail.com> wrote:

Hi
Why do I get an error (ruby 2.3.0)?
[1,2,3]&.upcase
What am I doing wrong here?
(I know there is no Array.upcase)

Thanks
Berg

Unsubscribe: <mailto:ruby-talk-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-talk&gt;

3

Hi
I want to understand the usage of & .
Thought this should produce no error!?

Thanks
Berg

4

Understand '&' under what context? Like a bit AND operator like this

irb(main):023:0> "%b" % (0b1111 & 0b1001)
=> "1001"

Focus on what's going on inside the round brackets ( ) with the 2 bit values.

The "%b" % at the start is to format the output to a binary format,
and the prefix '0b' is a way to represent a value in binary format.

···

On Sat, Apr 2, 2016 at 8:34 PM, A Berger <aberger7890@gmail.com> wrote:

Hi
I want to understand the usage of & .
Thought this should produce no error!?

Thanks
Berg

Unsubscribe: <mailto:ruby-talk-request@ruby-lang.org?subject=unsubscribe>
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--
Kind Regards,
Rajinder Yadav

SafetyNet Test Driven Development
http://safetynet.devmentor.org

5

The "safe navigation operator" &. _only_ prevents NoMethodError
when the calling object is nil, not for any other object.
Its purpose is to avoid nil checks.

You can find examples e.g. here:

http://mitrev.net/ruby/2015/11/13/the-operator-in-ruby/

Regards,
Marcus

···

Am 03.04.2016 um 02:34 schrieb A Berger:

I want to understand the usage of & .
Thought this should produce no error!?

--
GitHub: stomar (Marcus Stollsteimer) · GitHub
PGP: 0x6B3A101A

6

`a&.b` is like `a && a.b`

   nil&.foo #=> nil
   'x'&.foo #=> no method error

···

On 03/04/2016 10:35 AM, "A Berger" <aberger7890@gmail.com> wrote:

Hi
I want to understand the usage of & .
Thought this should produce no error!?

Thanks
Berg

7

almost...

  false&.foo # => NoMethodError
  false && false.foo # => false

Regards,
Marcus

···

Am 03.04.2016 um 05:24 schrieb Matthew Kerwin:

`a&.b` is like `a && a.b`

   nil&.foo #=> nil
   'x'&.foo #=> no method error

--
GitHub: https://github.com/stomar/
PGP: 0x6B3A101A

8

Indeed, which is why I didn't say it's "the same as," just "like." It also
only invokes the receiver once:

    def a() puts 'a'; 'a'; end
    def b() puts 'b'; 'b'; end

    a && a.upcase # prints twice
    b&.upcase # prints once

Cheers

···

On 3 April 2016 at 18:11, <sto.mar@web.de> wrote:

Am 03.04.2016 um 05:24 schrieb Matthew Kerwin:
> `a&.b` is like `a && a.b`
>
> nil&.foo #=> nil
> 'x'&.foo #=> no method error

almost...

  false&.foo # => NoMethodError
  false && false.foo # => false

Regards,
Marcus

--
  Matthew Kerwin
  http://matthew.kerwin.net.au/

9

Sorry, I didn't catch that fine distinction :slight_smile:

···

Am 03.04.2016 um 11:20 schrieb Matthew Kerwin:

Indeed, which is why I didn't say it's "the same as," just "like."

--
GitHub: stomar (Marcus Stollsteimer) · GitHub
PGP: 0x6B3A101A

10

Hi all,
Thanks for that many very explainative answers;
much more details than could be found in the internet :slight_smile:
- and also helpful for all (others)!

Berg