[ruby-core:84017] [Ruby trunk Feature#12753] Useful operator to check bit-flag is true or false

Issue #12753 has been updated by aycabta (Code Ahss).


phluid61 (Matthew Kerwin) wrote:
> It introduces a strange paradox, though:
> 
> ~~~ruby
> a.allbits? 0 #→ true
> a.nobits? 0  #→ true
> ~~~

I discussed it with @watson1978 (Shizuo Fujita). We guess the behavior is not strange.

The allbits? means "The receiver checks that all standing bits of the argument don't sit on itself".

~~~ruby
a.allbits? 0 #→ true
~~~

In this case, "all standing bits of the argument don't sit on the receiver " because "all standing bits of argument" is nothing. So it returns true. I think this is correct. If I have to choose a word, it's reasonable specification.

~~~ruby
a.nobits? 0  #→ true
~~~

I think this is correct in the same way.

----------------------------------------
Feature #12753: Useful operator to check bit-flag is true or false
https://bugs.ruby-lang.org/issues/12753#change-68098

* Author: tagomoris (Satoshi TAGOMORI)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Ruby's 0 is truthy value. It's useful for many cases, but it's confusing and I made many bugs when I'm writing code to handle binary data, because my thought is almost same with one to write C code in such situation.

```ruby
n = get_integer_value
if n & 0b10100000
  # code for the case when flag is true
else
  # never comes here :(
end
```

IMO it's very useful to have methods for such use-cases, like `#and?` and `#xor?` (`#or?` looks not so useful... I can't imagine the use case of this operator, but it's better to have for consistency).

```ruby
n = get_integer_value
case
when n.and?(0b10000000)
  # negative signed char
when n.and?(0b01110000)
  # large positive
else
  # small positive
end
```




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>