Le 09/11/2012 07:53, Nick Sabalausky a écrit :
On Thu, 08 Nov 2012 21:24:49 -0800
Jonathan M Davis<jmdavisp...@gmx.com> wrote:
On Thursday, November 08, 2012 21:10:55 Walter Bright wrote:
Many algorithms (at least the ones in Phobos do) already do a check
to ensure the inputs are the correct kind of range. I don't think
you'll get very far trying to use a range that isn't a range.
Of course, you can always still have bugs in your range
implementation.
Given that a range requires a very specific set of functions, I find
it highly unlikely that anything which isn't a range will qualify as
one. It's far more likely that you screw up and a range isn't the
right kind of range because one of the functions wasn't quite right.
There is some danger in a type being incorrectly used with a function
when that function requires and tests for only one function, or maybe
when it requires two functions. But I would expect that as more is
required by a template constraint, it very quickly becomes the case
that there's no way that any type would ever pass it with similarly
named functions that didn't do the same thing as what they were
expected to do. It's just too unlikely that the exact same set of
function names would be used for different things, especially as that
list grows. And given that ranges are a core part of D's standard
library, I don't think that there's much excuse for having a type
that has the range functions but isn't supposed to be a range. So, I
really don't see this as a problem.
Looking at one set of interfaces in isolation, sure the chances might
be low. (Just like the chances of name collisions when hygeine is
lacking, and yet we thankfully have a real module system, instead of C's
clumsy "Well, it should usually work ok!" garbage.) But it's a terrible
precedent. Scale things up, use ducks as common practice, and all of a
sudden you're right back into the same old land of "no-hygeine". Bad,
sloppy, lazy precedent. AND the presumed benefit of the duckness is
minimal at best. Just not a good design, it makes all the wrong
tradeoffs.
UDA is a really good way to express that intent.
