crystal 1.6.0+dfsg-2 (amd64 binary) in ubuntu lunar

 The Crystal's language syntax is inspired by Ruby, the language is statically
 type-checked but does not require that the type of variables or method
 arguments be specified.
 .
 The language has the following goals: (1) have the same syntax as Ruby, or at
 least as similar as possible; (2) statically type-checked but without having
 to specify the type of variables or method arguments; (3) be able to call C
 code by writing bindings to it in Crystal; (4) have compile-time evaluation
 and generation of code, to avoid boilerplate code; (5) compile to efficient
 native code.