Tube: A subway route planner in Dyalog APL (2011) (dfns.dyalog.com)

The code itself is here: https://dfns.dyalog.com/tube_code.htm

I'm not an expert in APL-family languages, but they seem to be perfect for those who have developed an intense hatred of boilerplate and explicit loops.

Sometimes I think I understand computation, then I look at APL.