Issue #16670 has been updated by shevegen (Robert A. Heiler).


I do not think reddit discussions are that useful, largely because it is difficult to find
what is really going on (content-to-noise ratio), and the article title was actually
"2.7's pattern matching official docs (recently merged)". zverok is active here on the
bugtracker, though, so I suppose he can comment on this issue if he has time and is
motivated. :)

If I understood your comment, then you refer mostly to the " in " part, and not regular
pattern-matching via case/in, yes?

If this is the case, and if I do not remember incorrectly, then I think the one-line
" in " was suggested by mame, not by the original author who suggested pattern matching.
(I mention this just so there is no confusion, because we should be clear with this -
ruby users may be confused about which syntax is valid, and which one is not, even
more so when it would suddenly change.)

Personally I have no specific opinion either way, largely because I am sticking to 
what is very simple for me to understand; and pattern matching, while interesting, 
is way over my head. :D But specifically, it may be best if mame and zverok could
comment on the proposal, if possible, to compare trade-offs, in particular upon
this:

    expression in {pattern: something}

versus

    {pattern: something} in expression.


----------------------------------------
Feature #16670: Reverse order of `expression` in `pattern` for 1-line pattern matching while it's still experimental
https://bugs.ruby-lang.org/issues/16670#change-84465

* Author: ttilberg (Tim Tilberg)
* Status: Open
* Priority: Normal
----------------------------------------
Currently the 1-line syntax for pattern matching is:

```
# Usage: <expression> in <pattern>

expression = {
  pattern: "Example"
}

expression in {pattern: something}
# something => "Example"
```

Is it technically possible, and desirable to switch the order of this syntax to:

```
# Usage: <pattern> in <expression>

expression = {
  pattern: "Example"
}

{pattern: something} in expression
# something => "Example"

```
?

Here are my reasons:

- It is more intuitive in English -- we are "finding a pattern in something". Finding "something in a pattern" doesn't seem to make sense.
- Assignment is happening, and this keeps assignment on the left side of the operator which feels more natural.
- It matches existing behavior with the workings of the case statement:

Understanding that a `case` block evaluates each `when` expression using `when_expression === case_expression` makes more consistency with `when_pattern in case_pattern` using the new operator.

```
case something
when /pattern/
end

# is equivalent to

/pattern/ === something

# This creates more parity with

case something
in {pattern: x}

# would be equivalent to

{pattern: x} in something
```


Please see the following discussion on Reddit: https://www.reddit.com/r/ruby/comments/favshb/27s_pattern_matching_official_docs_recently_merged/fj2c7ng/



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