Convert Ruby ranges to regular expressions

Andrei Kaleshka

23 Mar 2015

Recently I noticed that there is no a Rubyß library that allows to convert Ruby ranges to regular expressions. That’s why I decided to write it by myself and this post is just a sharing the gem’s link and a few examples how to use the gem.

Problem

Assume you have a Ruby range and have to transform it to a regular expression. Say, you have -9..9 and have to get /-[1-9]|\d/. For the first glance the solution looks rather easy but to get an optimized solution it requires a lot of time if you don’t know an algorithm to do this.

Recently I had to solve an issue like this and, honestly, I couldn’t solve the task in 2 hours. Then I started to search a ready solution in Google and finally I found its implementation in Python. Thankfully my curiosity I’ve already learned Python and could manage to translate the algorithm into Ruby within 1 hour. And finally I released a gem with the algorithm.

So if you have the issue the gem may be helpful for you.

Solution

The gem is called range_regexp and located here.

These are few examples of its usage:

require 'range_regexp'
converter = RangeRegexp::Converter.new(-9..9)
converter.convert # => /-[1-9]|\d/
converter = RangeRegexp::Converter.new(12..3456)
converter.convert # =>/1[2-9]|[2-9]\d|[1-9]\d{2}|[1-2]\d{3}|3[0-3]\d{2}|34[0-4]\d|345[0-6]/

Conclusion

Now we can convert ranges to regular expressions easily using Ruby. You don’t have to reinvent a wheel, just get the gem and use it. If you have any suggestions or questions, feel free to contact me.