...because it is apparently more efficient in some cases. Technically
we don't do this in ALL places, because it would be unfortunate if
the implementation of _successorInPlace() were self recursive :-)
At DaveA's suggestion, I took a mostly mechanical approach to this:
pointers and numeric types start using += 1, and indexes use
i = i.successor(). The index model is likely to be revised in
Swift 3 anyway, so micro-optimizing this code syntactically isn't
super important.
There is some performance concern of this patch, since some
in-place succesor operations are more efficient than
i = i.successor(). The one that seems particularly at issue is the
instance in the implementation of partition(), which I changed to
use i._successorInPlace(). If other instances lead to a perf issue,
they can be changed to use that as well.
- Add Strict/Defaulted Index types to StdlibUnittest
- Test whether a random access index calls its more efficient
customization by tracking successor calls.
- Fix the RandomAccessIndex.advancedBy(n, limit:) API by de-underscoring
the limit parameter
- Inline some internal transparent default implementations to their only
call site
- Attach _RandomAccessAmbiguity type to RandomAccessIndex
rdar://problem/22085119
Swift SVN r30979
- Remove free Swift functions for advance and distance and replace
them with protocol extension methods:
- advancedBy(n)
- advancedBy(n, limit:)
- distanceTo(end)
- Modernize the Index tests
- Use StdlibUnittest
- Test for custom implementation dispatch
Perf impact: No significant changes reported in the
Swift Performance Measurement Tool.
rdar://problem/22085119
Swift SVN r30958
The rule changes are as follows:
* All functions (introduced with the 'func' keyword) have argument
labels for arguments beyond the first, by default. Methods are no
longer special in this regard.
* The presence of a default argument no longer implies an argument
label.
The actual changes to the parser and printer are fairly simple; the
rest of the noise is updating the standard library, overlays, tests,
etc.
With the standard library, this change is intended to be API neutral:
I've added/removed #'s and _'s as appropriate to keep the user
interface the same. If we want to separately consider using argument
labels for more free functions now that the defaults in the language
have shifted, we can tackle that separately.
Fixes rdar://problem/17218256.
Swift SVN r27704
The performance regression that occurred when ++ and -- were added as
requirements to the Index protocols was due to the fact that it caused a
dubious hack of mine to be bypassed: when treated as indices, integer
types are incremented and decremented without overflow checking. While
technically justifiable (see the r20576 commit message), this makes the
standard library extremely fragile and makes successor() and
predecessor() mathematically unsafe. We really should see what the
optimizer team can do to make that hack unnecessary.
In the meantime, instead of dispatching through ++ and --, use a
special, defaulted _[successor|predecessor]InPlace() method to give
indices their own, customizable in-place inc/dec-rement path.
Swift SVN r26926
The standard library has grown significantly, and we need a new
directory structure that clearly reflects the role of the APIs, and
allows future growth.
See stdlib/{public,internal,private}/README.txt for more information.
Swift SVN r25876
