[tel]

If you like this then you should check out the source, Richard Bird's book [0] for it and many other similar examples.

[0] http://www.amazon.com/Pearls-Functional-Algorithm-Design-Ric...

[jacksontale]

Yeah, I formally introduced the book when I presented the pearl 1: http://typeocaml.com/2015/02/02/functional-pearl-no-1-the-mi...