And in a real functional language like F#... let authorsOfLongBooks = books |> Seq.filter (fun book -> book.pageCount > 1000) |> Seq.map (fun bo

And in a real functional language like F#... let authorsOfLongBooks = books |> Seq.filter (fun book -> book.pageCount > 1000) |> Seq.map (fun book -> book.author) |> Seq.distinct ...you can set breakpoints anywhere in the pipeline!