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LazyCollection.swift.gyb
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LazyCollection.swift.gyb
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//===--- LazyCollection.swift ---------------------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
%for traversal in [ 'Forward', 'Bidirectional', 'RandomAccess' ]:
% whereClause = 'where S.Index : %sIndexType' % traversal
% Self = 'Lazy%sCollection' % traversal
/// A collection that forwards its implementation to an underlying
/// collection instance while exposing lazy computations as methods.
public struct ${Self}<S: CollectionType ${whereClause}> : CollectionType {
/// Construct an instance with `base` as its underlying collection
/// instance.
public init(_ base: S) {
self._base = base
}
/// Return a *generator* over the elements of this *sequence*.
///
/// Complexity: O(1)
public func generate() -> S.Generator {
return self._base.generate()
}
/// The position of the first element in a non-empty collection.
///
/// Identical to `endIndex` in an empty collection.
public var startIndex: S.Index {
return _base.startIndex
}
/// The collection's "past the end" position.
///
/// `endIndex` is not a valid argument to `subscript`, and is always
/// reachable from `startIndex` by zero or more applications of
/// `successor()`.
public var endIndex: S.Index {
return _base.endIndex
}
/// True if and only if the collection is empty
public
var isEmpty: Bool {
return startIndex == endIndex
}
/// The first element, or `nil` if `self` is empty
public var first: S.Generator.Element? {
return Swift.first(self)
}
% if traversal != 'Forward':
/// The last element, or `nil` if `self` is empty
public var last: S.Generator.Element? {
return Swift.last(self)
}
% end
/// Access the element at `position`.
///
/// Requires: `position` is a valid position in `self` and
/// `position != endIndex`.
public
subscript(position: S.Index) -> S.Generator.Element {
return _base[position]
}
/// an Array, created on-demand, containing the elements of this
/// lazy CollectionType.
public var array: [S.Generator.Element] {
return Array(_base)
}
var _base: S
}
public func ~> <S : CollectionType ${whereClause}> (
s: ${Self}<S>, _: (_UnderestimateCount, ())
) -> Int {
return underestimateCount(s._base)
}
/// Augment `s` with lazy methods such as `map`, `filter`, etc.
public
func lazy<S: CollectionType ${whereClause}>(s: S) -> ${Self}<S> {
return ${Self}(s)
}
%end
// ${'Local Variables'}:
// eval: (read-only-mode 1)
// End: