Program Description Based Programming

I introduce Program Description Based Programming (PDBP).
Notice that the pipe on the picture is a description of a pipe.

This is the first meetup of series of meetups.
I am planning to write a book about this.
The book is similar to (but also different from) the "Functional Programming in Scala" book of Runar. I'll try to keep the meetups as simple as possible in order not to loose too many attendees :-)

Transport:

• train
  10 min walk from Station Gent Dampoort

• car
  parking on public road

What to bring:

Nothing.

Remark:

The code that I show is written in Dotty.
The difference with Scala is minimal (after all Dotty will be the next Scala).