Postfix `!?` can use as the valid function identifier.
This patch make it possible to parse and execute such a code:
def foo!? true end foo!?
When is this patch useful?
Let's say, there are two methods. One method named
ExampleDB#exists?(id) which is to request SQL has I/O side effects, another method named
ExampleCollection#exists?(id) which is to find
id in memory has no I/O side effects. Calling costs of these methods are different, but we can't know it by code on calling
In general case, when we want to make the method having to modify object and return boolean value, this patch is useful. Of course such a method is not good, however we are unavoidable to write good efficient program, aren't we?
What effects dose this change have?
For example, snippet
foo!?1:2 is interpreted to call method
foo! and ternary operation now, but after applying this patch it raises syntax error. Although we can escape this problem by spacing between
I think that this problem is tiny, but it is incompatible change.
Why is postfix
!? only? I want to use
This is the religious problem. If you are Python user, you believe Zen of Python:
There should be one-- and preferably only one --obvious way to do it.
Or if you are Perl user, you believe TMTOWTDI:
There’s more than one way to do it.
I am not Perl nor Python user. But, this issue's purpose is naming identifier more clearly, so I adopted only
Updated by matz (Yukihiro Matsumoto) over 5 years ago
- Status changed from Open to Feedback
First of all, this is a proposal for incompatible change, so we have to be very careful.
Besides that, I am afraid you have two misunderstandings. (a) in Ruby, "!" is not for methods with side effect, unlike Scheme. (b) predicates (methods with "?") should not have side effect, this is a rule of thumbs.
In summary, we have to reject the proposal, unless you have unseen use-cases.