This code as written is not sound and should not type check
for non-final classes conforming to SequenceType (eg, NSArray).
Instead, capture the base of the call from the preprocess closure
passed in. The closure is @noescape, so it should be equivalent.
For lazy collections, `isEmpty` and `startIndex` may be O(N) operations.
The old implementation ended up being potentially O(2N) instead of O(1).
In particular, accessing `col.lazy.filter(pred).first` would evaluate
the predicate on elements twice, once to determine the result of
`isEmpty` and once to determine `startIndex`.
...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.
This commit simplifies map() of collections into a simple append-loop. The Swift
optimizer can do a better job optimizing code without unsafe constructs. This
change accelerates the MapReduce benchmark by 2x.
- 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
See doc comments on MutableSlice for more information about what it is.
MutableSlice was one of the reasons to clarify and tighten index
invalidation rules. After that change, existing MinimalCollection
test types were performing checks that are too strict according to the
model. Existing algorithms and collections could provide them, but not
MutableSlice. This commit updates MinimalCollection types to perform
index invalidation checks that correspond to new rules.
Part of rdar://20722366. This commit adds the type, but does not wire
it up completely yet.
Swift SVN r30839
The type checker hits a recursion when checking the conformance to
CollectionType in UnsafeMutableBufferPointer, which requires
_withUnsafeMutableBufferPointerIfSupported, which mentions
UnsafeMutableBufferPointer. The easiest fix for now is to break the
recursion in the library.
Reverting this change is tracked by: <rdar://problem/21933004> Restore
the signature of _withUnsafeMutableBufferPointerIfSupported() that
mentions UnsafeMutableBufferPointer
Swift SVN r30838
Replace the Lazy-based implementations with open-coded implementations based on the _UnsafePartiallyInitializedContiguousArrayBuffer builder from the previous commit, so that we have control over the early-exit flow when an error interrupts the operation.
Swift SVN r30794
Including:
- forEach
- split
- Optional flatMap
- minElement
- maxElement
- startsWith
- elementsEqual
- lexicographicalCompare
- contains
- reduce
Still not touching 'map', 'filter', 'flatMap', or 'sort', which need various levels of rearchitecting to fix.
Swift SVN r30792
This covers:
- Lifetime-extending wrappers, like withExtendedLifetime, withCString, and withUnsafe*Pointer
- 'map' and friends on Optional
- 'indexOf'
A few APIs I haven't gotten to yet in this first pass:
- Autoclosure APIs, like assert, &&, etc.
- the 'isOrderedBefore' predicate for sorting APIs. The sorting implementation does some microoptimizations with 'inout' closures that violate rethrows checking.
- Strict 'map', 'filter', and friends on CollectionType. These need some plumbing in Lazy to be able to thread a Result-forming transformation through.
This version of the patch updates some protocol customization implementations that I missed the first time around, and includes the tests I forgot to add in the previous iteration.
Swift SVN r30790
This covers:
- Lifetime-extending wrappers, like withExtendedLifetime, withCString, and withUnsafe*Pointer
- 'map' and friends on Optional
- 'indexOf'
A few APIs I haven't gotten to yet in this first pass:
- Autoclosure APIs, like assert, &&, etc.
- the 'isOrderedBefore' predicate for sorting APIs. The sorting implementation does some microoptimizations with 'inout' closures that violate rethrows checking.
- Strict 'map', 'filter', and friends on CollectionType. These need some plumbing in Lazy to be able to thread a Result-forming transformation through.
Swift SVN r30597
They pass various operations through to the base
collection (e.g. LazyMapCollection's .count) and thereby avoid taking
the potentially-slower path through the default implementation.
Swift SVN r30554
Add a default implementation for CollectionTypes where their SubSequence
== Self. That is, mainly, Slice and ArraySlice. This changes the slice's
view of, but not modifying or copying, the underlying collection.
rdar://problem/20302034
Swift SVN r30496
- De-underscore the API that takes an equatable separator, add doc
comment, and add a test for it.
- Add a test for the negative maxSplit case.
- Add lifetime tracker for isSeparator closure in the semantic test.
Swift SVN r30413
rdar://problem/21663830
Add the following new requirements to SequenceType with default implementations:
- dropFirst(n)
- dropLast(n)
- prefix(n)
- suffix(n)
- split(n)
In addition, provide specialized default implementations of these for CollectionTypes with forward, bidirectional, and random-access Index types where possible.
Add the following new requirements to CollectionType with default implementations:
- prefixThrough(n)
- prefixUpTo(n)
- suffixFrom(n)
- split() // isSeparator closure
Add the following convenience APIs:
- dropFirst() -> calls dropFirst(1)
- dropLast() -> calls dropLast(1)
Add a tentative underscored API:
- split() // takes Equatable separator.
Some APIs have undefined behavior when creating slices where the endpoints go beyond the bounds of the underlying collection. This will be fixed later by trapping creation of slices with invalid indices (rdar://problem/21822657).
Swift SVN r30371
