pu$�le

[strtr]

== Quote from Jonathan M Davis (jmdavisprog at gmail.com)'s article
> On Saturday 17 July 2010 18:59:18 strtr wrote:
> > That is [dollar sign, euro sign]
> >
> > The reason I post it is because I expected the stash to be 3 lower.
> As to why it's not working right, change th foreach loop to this:
> foreach(dchar coin; coins)
> {
> ...
> }
> Otherwise, instead of looping over each code point, you're looping over each
> code unit. char[] and string are encoded in utf-8, so each char is a code unit,
> and 1 - 4 code units are put together to form a code point, which is what you'd
> normally think of as a character.
> The dollar sign takes one code unit in utf-8, but the euro sign takes 3. So,
> you're looping 4 times instead of 2. By specifying dchar, the compiler
> automatically processes the code units correctly to make it so that you loop
> over each code point (i.e. character) rather than each code unit (i.e. char).
> You should pretty much never deal with each individual char or wchar in a string
> or wstring. Do the conversion to dchar or dstring if you want to access
> individual characters. You can also use std.utf.stride() to iterate over to the
> next code unit which starts a code point, but you're still going to have to make
> sure that you convert it to a dchar to process it properly. Otherwise, only
> ASCII characters will work right (since they fit in a single code unit).
> Fortunately, foreach takes care of all this for is if we specify the element
> type as dchar.
> As for why it's 4 rather than 2 in the corrected version (or 8 instead of 4 in
> the incorrect version), that's because you have both scope(exit) and
> scop(success) there. Both will be run, so both will increment stash, and you get
> double the increments that you seem to be expecting.
> - Jonathan M Davis

Wasn't it obvious the puzzle was about exceptions, with half of the lines being
scope guards and all?
Part of the puzzle is the realization that chars aren't code points but code units.
The other part is understanding the order of scope guard execution.
I'm not sure whether the linux or the windows version of writef is the correct
one, but here I get a nice utf-exception. (Or did you maybe use D2? if not then we
have a discrepancy bug)