Why does the Gemfile semantic versioning operator (~>) produce inconsistent results with one number?

Question

The gemspec semantic versioning operator ~> (aka twiddle-wakka, aka pessimistic operator) allows a gem version to be constrained yet allow some upgrades.

I have oft

Answer 1

By peeking into rubygems sources (esp. requirement.rb, version.rb) the pessimistic operator needs at least two versioning segments.

It also does make a sense. As ~> v.r is just a syntactic sugar for inequality

v.r <= current_version.current_release < (v+1).0

what would be the upper bound if there is only one version number ? Yep, ∞ (infinity), so there is no point why it should work. You can simply write it as >= v .