For the few weeks so far, I have been practicing ruby on multiple platforms (Atcoder and BOJ, solved about ~150 in total?). Now I feel that I am fluent enough with the language, so I will be using Ruby, along with Python 3 and C++, on todays Round (the Div.3). After that, I would like to share my honest thoughts about using Ruby in CP with others as well. I am eager to see how well Ruby can perform on Codeforces today!

P.S. Yes, I am writing this blog also for the ignorant people who might argue about this saying that I am cheating again, why can't they understand that one person can understand more than 2~3 languages? (Yes, I could've used Ruby, Java, C++, Python, and JS all in the same contest. I simply don't because there's no merit for that.)

UPD: The round has concluded. I solved 4 tasks in total, 3 with Ruby and 1 with Python, and then tried 2 more tasks with C++. (Could not come up with the idea on E, could not come up with the edge cases on G. This is not to argue with the contest's difficulty; the tasks were good, I was just not good enough.)

My impression about this? It's quite amazing. I could do almost everything I can do with Python on Ruby, and the code was shorter most of the time. This gives me a great advantage — I can type less and think more. That's a great advantage. Task A and Ruby made a very funny result, coming up with the following solution.

gets.to_i.times do
    puts eval gets
end

Ruby and Python do share many characteristics — short code, arbitrary precision integers, etc. However, Ruby supports more out-of-the-box, like fractions and complex numbers without any "imports". (arbitrary precision decimal types are supported, but they are in a separate module in the standard library.) And Ruby supports even more with standard libraries, exceeding what you may have imagined a language would have as a built-in feature. Who would have imagined a language would have Tarjan's SCC algorithm built-in? Or multidimensional Newton's method? The language has been performing much better than I have initially imagined, and is constantly getting beyond my imagination. If someone would like to learn a new language for CP (anything other than C++), I would greatly recommend them to learn Ruby.

Ruby does have its flaws, though. Ruby has a very small call-stack size limit by default, for which I am asking for an improvement to Codeforces. The language is also slow, probably on par with Python. But even considering these flaws, Ruby seems to be very performant in the CP scene. (At least, it is better than Python IMO)

TL;DR: It's a great language for CP, and I am very surprised.