Example within documentations of D seriously need some improvement.

[Andrej Mitrovic]

> If you have a 100 line example

There's a few (I think?) of those in the docs. There was one such
example for associative arrays which I've refactored a bit. And it
does use writeln, as it should.

The nice thing about that example is that it's at the end of the page,
showcasing how hashes can be used, so it's kind of a wrap-up of
everything learnt by the user who reads that page. Maybe we should
have more of these types of examples for each topic. In those cases
writeln makes a lot of sense.

Hopefully actual examples will be autotested one day. Otherwise they
can go out-of-date in-between releases.

Btw, TDPL introduces assert as soon as page 10. And the book is quite
assert-heavy overall, although writeln is used as well.