pu$�le

[strtr]

== Quote from Jonathan M Davis (jmdavisprog at gmail.com)'s article
> On Saturday 17 July 2010 21:48:30 strtr wrote:
> > == 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)
> All I ever use is D2. I have no idea what D1 would be doing differently. In D2,
> writef(), the "f" is for format or formatted, and you have to have a "format"
> string like printf would in order for it to work. write() is the version which
> doesn't require a format string. I am using Linux if that changes anything, but
> as far as I can tell, you're using writef() incorrectly. In any case, I
> obviously don't quite get what you're trying to do since (at least in D2), I
> don't believe that you have any functions in that loop which will every throw an
> exception. If you were using File's writef() because you were writing to a file,
> then that would be different. But writef() by itself is to stdout and won't
> throw.
> Now, as you're using D1, that may change things. But you gave no indication that
> you were using D1. In future questions, you should probably be more specific
> about that, since I think that most people around here are using D2, and they
> will likely assume that you're using D2 unless you say otherwise. I certainly
> did.
> - Jonathan M Davis
I think I'll start subject tagging my posts: [D1/D2]
std.stdio in D1 doesn't mention a write function and feeding the writef function
an illegal UTF string will result in a UTF exception.
With this information, what do you think the output should be?