可能重复：
版本要求中波浪号大于（~>）的含义？
我在gemspec:中经常看到这样的东西
s.add_dependency 'some_gem', '~> 1.5.0'
>>是什么意思？
来自gembundler
The specifier ~> has a special meaning, best shown by example.
~> 2.0.3 is identical to >= 2.0.3 and < 2.1.
~> 2.1 is identical to >= 2.1 and < 3.0.
~> 2.2.beta will match prerelease versions like 2.2.beta.12.