From: sawadatsuyoshi@...
Date: 2017-01-03T15:10:30+00:00
Subject: [ruby-dev:49940] [Ruby trunk Feature#13067] TrueClass, FalseClass to provide `===` to match truthy/falsy values.

Issue #13067 has been updated by Tsuyoshi Sawada.


Marc-Andre Lafortune wrote:

> 2) There is no good replacement for the current uses of `when true` and `when false`. In particular, `when true` would basically require separate `if`.
> 
>       # From rails/actionpack/lib/action_dispatch/middleware/ssl.rb
>       # Current:
>       def normalize_hsts_options(options)
>         case options
>         when false
>           # ...
>         when nil, true
>           # ...
>         else
>           # ...
>         end
>       end
> 
>       # Ugly rewrite necessary:
>       def normalize_hsts_options(options)
>         if options == true
>           # ...
>         else
>           case options
>           when nil
>             # repeated code from `options == true` above...
>           when false  # `nil` case must be already taken care of
>             # ...
>           else
>             # ...
>           end
>       end

I think there is an alternative.

```
case options
when TrueClass
  ...
when NilClass, FalseClass
  ...
...
end
```

In fact, I had often felt there is redundancy between `when true` etc. and `when TrueClass` etc., and had to wonder which one to use. If they would mean different things, as would be the case if this proposal is implemented, then that would be a desired move, I think.


----------------------------------------
Feature #13067: TrueClass,FalseClass to provide `===` to match truthy/falsy values.
https://bugs.ruby-lang.org/issues/13067#change-62369

* Author: Yukihiro Matsumoto
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Target version: 
----------------------------------------
I propose to make `TrueClass`, `FalseClass` to provide `===` method to match truthy values (`TrueClass`), and falsy values (`FalseClass`), so that we can use true and false for case pattern matching.  And we can pick truthy values using `grep` e.g. `ary.grep(true)`.

Matz.



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