$ whois crystal

Crystal

first released in 2014 · by Ary Borenszweig, Juan Wajnerman, Brian Cardiff

$ guessprog --inspect crystal

year: 2014
paradigm: object oriented
family: other
memory: automatic gc
binding: static
safety: strong

CRYSTAL(7)

AUTHORS: Ary Borenszweig, Juan Wajnerman, Brian Cardiff
HISTORY: Ary Borenszweig, Juan Wajnerman and Brian Cardiff started Crystal in 2011 at Manas Technology Solutions in Buenos Aires, aiming to combine Ruby's elegant syntax with the speed and type safety of a compiled language. It was briefly called Joy before being renamed. The first compiler was written in Ruby, but by 2013 Crystal could compile itself. A global type inference algorithm means types are checked at compile time while rarely being written down, and version 1.0 arrived in 2021.
USAGE: A niche language with a small but active community, used mainly for web services, command-line tools and by Ruby developers who want native performance.
SEE ALSO: Crystal on Wikipedia ↗

$ cat describe.cr

def describe(value : Int32 | String)
  case value
  when Int32  then "a number, doubled: #{value * 2}"
  when String then "a string, upcased: #{value.upcase}"
  end
end

puts describe(21)
puts describe("crystal")

name = ENV["USER"]?   # type is String | Nil
puts name.try(&.capitalize) || "anonymous"