[ruby-core:78451] [Ruby trunk Feature#12753] Useful operator to check bit-flag is true or false

Issue #12753 has been updated by Shugo Maeda.


Shugo Maeda wrote:
> IBM InfoSphere and MS FoxPro have BITTEST(), but its second argument is the bit position
> to be tested.
> 
> http://www.ibm.com/support/knowledgecenter/SSZJPZ_11.3.0/com.ibm.swg.im.iis.ds.basic.doc/topics/r_dsbasic_BITTEST_function.html
> https://msdn.microsoft.com/en-us/library/aa977348(v=vs.71).aspx
> 
> This behavior seems to fit the name bittest, compared to the proposed one.

I didn't mean to propose this behavior.
I just meant to point out that `bittest?` may not be suitable for the proposed behavior.


----------------------------------------
Feature #12753: Useful operator to check bit-flag is true or false
https://bugs.ruby-lang.org/issues/12753#change-61822

* Author: Satoshi TAGOMORI
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
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
```




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