rspec/rspec-expectations — pull request #145 by zhangsu (2012-05-17 03:41:04+00:00)
Title: Fix confusing error message in `be_within`

This is a patch for [this issue](https://github.com/rspec/rspec-expectations/issues/92).

It is possible to have duck typing for numerical operations, but the minus
sign is often used for other operations as well such as the set
difference that Array#- performs. In that case, even if it does not fail
on the :- method, it will probably fail on the subsequent :abs and :<=
calls.