Feature #5899: chaining comparsions.

• Status: Rejected
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[neleai (Ondrej Bilka)]

Migration from python to ruby is problematic because ruby lacks certain features.
Most important python advantage is chained comparison
We must wrap every comparison like described below.

puts "yes" if 1<2<3<4

class Fixnum
  def <(a)
    ((self<=>a)==-1)&&a
  end
end
class FalseClass
  def <(a)
    false
  end
end

Ondrej Bilka wrote in post #1041080:

Issue #5899 has been reported by Ondrej Bilka.

---

Feature #5899: chaining comparsions.
https://bugs.ruby-lang.org/issues/5899

puts "yes" if 1<2<3<4

+1

--
Posted via http://www.ruby-forum.com/.

[kernigh (George Koehler)]

What is a good way to do chained comparison in Ruby?

My best attempt, so far, is

[1, 2, 3, 4].each_cons(2).all? {|a, b| a < b}

[naruse (Yui NARUSE)]

• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

[matz (Yukihiro Matsumoto)]

• Status changed from Assigned to Feedback

I don't think changing "1 < b < 4" to "1 < b && b < 4" is that hard task.
I am not sure it's worth allowing confusing "false < 4".

Matz.

[mame (Yusuke Endoh)]

• Target version set to 2.6

[sos4nt (Stefan Schüßler)]

Yukihiro Matsumoto wrote:

I don't think changing "1 < b < 4" to "1 < b && b < 4" is that hard task.

Writing 1 < b && b < 4 is not hard. But doesn't 1 < b < 4 look intriguing? It's so clean!

I would also expect a slight difference, namely that 1 < b < 4 evaluates b once and 1 < b && b < 4 evaluates b twice.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[matz (Yukihiro Matsumoto)]

• Description updated (diff)

I don't think it's worth adding extra complexity to Ruby.

Matz.

[matz (Yukihiro Matsumoto)]

• Status changed from Feedback to Rejected

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)