@KennyLau Sure, that sounds good. I'd prefer to be sure of optimality, rather than posting a test case saying "the best I have is this but I don't know if we can do better"
llama@llama:...misc/oldstuffs/ruby$ ruby special\ numbers.rb
um hello
hi?
0, and that's all
what
llama@llama:...misc/oldstuffs/ruby$ wait what happened
llama@llama:...misc/oldstuffs/ruby$ ruby pi3.rb
Enter a number: no
Prime!
what???
Enter a number: you can't tell me what to do
Prime!
Enter a number: THAT WASN'T EVEN A NUMBER
Prime!
Enter a number: liar
Prime!
Enter a number: 10
Divisible by 2 (5)
Enter a number: 9
Prime!
Enter a number: rofl
So... uh... this is a bit embarrassing. But we don't have a plain "Hello, World!" challenge yet (despite having 35 variants tagged with hello-world, and counting). While this is not the most interesting code golf in the common languages, finding the shortest solution in certain esolangs can be a ...
Jelly, 26 bytes
ṙ1,-S+zµ⁺_|=3
ÇÐḶLỊẋ@ÇÐĿL’
Try it online! or verify all test cases.
Larger test cases (from @Katenkyo's answer): 15×15 stable | 15×14 glider
@KennyLau I think that's reduplication, but I'm not sure how we structured it in this case. It has been more than a month now since we thought it up, and none of us bothered to write it down till now :P
Your task is to convert a given positive integer from Arabic numeral to Roman numeral.
Things get difficult when you count to 4000.
The romans did this by adding a line above a symbol to multiply that symbol by 1 000. However, overlines aren't exactly displayable in ASCII. Also, there are doubl...