From: paradox.ver5@...
Date: 2020-06-13T00:30:33+00:00
Subject: [ruby-core:98775] [Ruby master Feature#16960] Feedback regarding `=>` in ‘As’ Pattern Matching

Issue #16960 has been reported by ParadoxV5 (���������������������������������� ���).

----------------------------------------
Feature #16960: Feedback regarding `=>` in ���As��� Pattern Matching
https://bugs.ruby-lang.org/issues/16960

* Author: ParadoxV5 (���������������������������������� ���)
* Status: Open
* Priority: Normal
----------------------------------------
The only obstacle preventing the use of non-symbol keys in hash patterns is simply the fact that `=>` is used for both `Hash`es and ���as��� patterns.
```ruby
case x
  in Integer => a, Float => b # Ambiguous
  in key: Symbol => value, **rest # Poor readability
  in Symbol => key => Symbol => value, **rest # ???
end
```
I recommend changing to something else. We can introduce the and operator `&`:
```ruby
case array in Float & 5 & five
  five.eql? 5.0 #=> true
end
```
And/Or, implement another operator explicitly for ���as��� patterns, say `:` (otherwise only used for *the* ternary operation) ���
```ruby
case x
  in Integer : a, Float : b
  in key: Symbol : value, **rest
  in Symbol : key => Symbol : value, **rest
end
```
��� which renders the pin operator `^` (and for those who *oppose*, their *unpin* operator(s)) unnecessary: expressions before it are always pinned values, and expressions after it are always `case`-`in` variable declarations.
```ruby
good = 8..10
okay = 5..7
skip = 0
case x
  in skip : # Syntax sugar for skip : _
    # skip
  in good : good_value
    puts good_value
  in okay : okay_value
	warn okay_value
  else : bad_value # Syntax sugar for BasicObject : bad_value
	raise bad_value.to_s
end
```
The second option still looks like an **un**pin operator for sugary code, however, if pinning values ���
```ruby
case array
  in :, : *all_but_first # Syntax sugar for BasicObject : _, BasicObject : *all_but_first
    p all_but_first
end
```
��� are somehow preferred over declaring variables:
```ruby
case array
  in _, *all_but_first # Current implementation
    p all_but_first
end
```
# Regarding `rescue`
We can���t change the `=>` part in `rescue`, of course; but we don���t need to. `Hash`es are not `Exception`s anyway.



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

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