On Saturday, 18 February 2012 at 23:26:14 UTC, Andrei
Alexandrescu wrote:
(b) all real code does one thing.
Andrei
No. It's conceivable that *most* cases simply log the exception
(e.g. by printing it) then either move back or move on (!). But
it's most definitely not *all* and it's when you have a
meaningful fall-back or recovery mechanism that exceptions shine
and it's what they're designed for (because you are basically
arguing against exceptions here, not their proper use, which
should be obvious from how they function).
The more complex your program becomes, the farther away from
uncontrollable factors like user input and otherwise unexpected
environments you get, and this is when interesting catch blocks
are born. Even so, exceptions are still useful in shallow parts
of your program too - you could catch a GetOptException (more
specific exception types than this with attached data would be
even better, as noted by everyone before me) and re-query the
user for new input (not very Unix-y, but that's irrelevant). You
can't do that with just an Exception - what if the exception came
from one of the callbacks you passed to getopt, or from a bug in
std.getopt?
All that said, I don't think std.getopt is a good example because
it's comparatively trivial code. std.file would be a much better
area to examine for examples of interesting catch blocks.
