From: matthew@...
Date: 2018-05-01T22:03:05+00:00
Subject: [ruby-core:86808] [Ruby trunk Feature#14724] chains of inequalities

Issue #14724 has been updated by phluid61 (Matthew Kerwin).


shan (Shannon Skipper) wrote:
> I've often seen new Rubyists try this syntax intuitively. I think this is a really nice change. +1

-1

I've seen beginners write all sorts of things. This makes it harder for experienced programmers.

Ruby has many innovations, many of which are great, but its fundamental operator chaining has always been pretty much the same as most other programming languages. 

----------------------------------------
Feature #14724: chains of inequalities
https://bugs.ruby-lang.org/issues/14724#change-71771

* Author: gotoken (Kentaro Goto)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
----------------------------------------
In mathematics, chain of inequations is a shorthand notation for the conjunction of several inequations involving common expressions. 

For example, `a < b <= c` for `a < b && b <= c`

Chain notation makes code clearer, in particular, long common expression cases will be so. E.g., 

```
cur.to_i - 2 <= timeval.tv_sec <= cur.to_i
```

is easier to read than

```
cur.to_i - 2 <= timeval.tv_sec && timeval.tv_sec <= cur.to_i
```

because in the latter case we have to verify whether `timeval.tv_sec` is common or not by eyes.

Current syntax allows but redefining builtin methods are considered not practical. So here I request as a new syntax for the chains.


### Use cases (applicable conjunctions)

lib/matrix.rb:
```ruby
    unless 0 <= column && column < column_count
```

lib/time.rb documents:
```ruby
    # block.  For example:
    #
    #     Time.parse(...) {|y| 0 <= y && y < 100 ? (y >= 69 ? y + 1900 : y + 2000) : y}
```

spec/ruby/optional/capi/bignum_spec.rb:
```ruby
  raise "Bignum#coerce returned Fixnum" if fixnum_min <= n && n <= fixnum_max
```

test/fiddle/test_import.rb:
```ruby
        assert(cur.to_i - 2 <= timeval.tv_sec && timeval.tv_sec <= cur.to_i)
```

tool/jisx0208.rb:
```ruby
        unless 0x8140 <= sjis && sjis <= 0xFCFC
```




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