On Mon, 06 Oct 2014 15:48:31 +0100, Jacob Carlborg <d...@me.com> wrote:
On 06/10/14 15:45, Andrei Alexandrescu wrote:
Knowledge doesn't have to be by type; just place data inside the
exception. About the only place where multiple "catch" statements are
used to make fine distinctions between exception types is in sample code
showing how to use multiple "catch" statements :o). This whole notion
that different exceptions need different types is as far as I can tell a
red herring.
What do you suggest, error codes? I consider that an ugly hack.
Why?
It gives us the benefits of error code return values:
- ability to easily/cheaply check for/compare them using "switch" on code
value (vs comparing/casting types)
- ability to pass through OS level codes directly
Without any of the penalties:
- checking for them after every call.
- losing the return value "slot" or having to engineer multiple return
values in the language.
- having to mix error codes in with valid return values (for int()
functions).
We also get:
- no type proliferation.
- no arguments about what exception types are needed, or the hierarchy to
put them in.
Seems like a win to me.
Of course.. it would be nicer still if there was a list of OS/platform
agnostic error codes which were used throughout phobos and could be
re-used by client code. And.. (for example) it would be nice if there was
a FileNotFound(string path) function which returned an Exception using the
correct code allowing:
throw FileNotFound(path);
and so on.
I do not know a lot about how exceptions are thrown and caught at the
compiler/compiled code level, but perhaps there is even a performance
benefit to be had if you know that only 2 possible types (Exception and
Error) can/will be thrown..
R
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