On Thursday, 4 April 2013 at 21:25:18 UTC, Jonathan M Davis wrote:
On Thursday, April 04, 2013 14:13:55 Ali Çehreli wrote:
On 04/04/2013 12:16 PM, Ali Çehreli wrote:
> core.exception.RangeError@deneme(125887): Range violation
I have realized something: Maybe some of the confusion here is
due to
range violation being an Error.
I think that it should be an Exception. The rationale is, some
function
is told to provide the element at index 100 and there is no
such
element. The function cannot accomplish that task so it throws
an
Exception. (Same story for popFront() of an empty range.)
My earlier comments about invalid program state apply to Error
conditions. (Come to think of it, perhaps even more
specifically to
AssertError.)
Those are Errors for arrays. Sure, someone could choose to
write their
containers or ranges in a way that throws an exception when you
try and access
an element that isn't there, but that then incurs a performance
cost for the
program as a whole, which would be particularly bad if the
standard library
then made that decision. In most cases, you know whether the
element is there
or not, and if you don't it's easy to check, so from an
efficiency standpoint,
it makes far more sense to treat out of bounds errors (which is
what
RangeError really is) as Errors. Phobos definitely take the
approach that
accessing an element in a range that isn't there is an Error
(be it by calling
popFront on an empty range or using opIndex to an element which
isn't there or
whatever), and in general, I think that that's very much the
correct approach.
There are obviously exceptions to that (e.g. the in operator),
but as far as
indexing, slicing, and popFront go, it should be considered a
programming bug
if they're used on elements that aren't there.
- Jonathan M Davis
It is where the current design choice make no sense.
If they are error, the recovery code isn't executed. Such
operation don't put the program in an invalid state (in fact, it
prevent the program to go in invalid state). In such situation,
not running that recovery code is likely to transform a small
error into a huge mess.
The case is very different from Ali's example before, where the
wrong file can be deleted.
