1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection
import generic._
import mutable.{Builder, AddingBuilder}
import PartialFunction._
/** A template trait for sets of type `Set[A]`.
*
* This trait provides most of the operations of a `Set` independently of its representation.
* It is typically inherited by concrete implementations of sets.
*
* $setnote
*
* @tparam A the type of the elements of the set
* @tparam This the type of the set itself.
*
* @author Martin Odersky
* @version 2.8
* @define setnote
* To implement a concrete set, you need to provide implementations of the
* following methods:
* {{{
* def contains(key: A): Boolean
* def iterator: Iterator[A]
* def +(elem: A): This
* def -(elem: A): This
* }}}
* If you wish that methods like `take`, `drop`,
* `filter` return the same kind of set, you should also override:
* {{{
* def empty: This
* }}}
* It is also good idea to override methods `foreach` and
* `size` for efficiency.
* @define coll set
* @define Coll Set
* @define willNotTerminateInf
* @define mayNotTerminateInf
*/
trait SetLike[A, +This <: SetLike[A, This] with Set[A]]
extends IterableLike[A, This]
with Addable[A, This]
with Subtractable[A, This] {
self =>
/* The empty set of the same type as this set
* @return an empty set of type `This`.
*/
def empty: This
/** A common implementation of `newBuilder` for all sets in terms
* of `empty`. Overridden for mutable sets in
* <a href="mutable/SetLike.html" target="ContentFrame">
* `mutable.SetLike`</a>.
*/
override protected[this] def newBuilder: Builder[A, This] = new AddingBuilder[A, This](empty)
/** Tests if some element is contained in this set.
*
* @param elem the element to test for membership.
* @return `true` if `elem` is contained in this set, `false` otherwise.
*/
def contains(elem: A): Boolean
/** Creates a new set with an additional element, unless the element is
* already present.
*
* @param elem the element to be added
* @return a new set that contains all elements of this set and that also
* contains `elem`.
*/
def + (elem: A): This
/** Creates a new set with a given element removed from this set.
*
* @param elem the element to be removed
* @return a new set that contains all elements of this set but that does not
* contain `elem`.
*/
def - (elem: A): This
/** Tests if this set is empty.
*
* @return `true` if there is no element in the set, `false` otherwise.
*/
override def isEmpty: Boolean = size == 0
/** Tests if some element is contained in this set.
*
* This method is equivalent to `contains`. It allows sets to be interpreted as predicates.
* @param elem the element to test for membership.
* @return `true` if `elem` is contained in this set, `false` otherwise.
*/
def apply(elem: A): Boolean = contains(elem)
/** Computes the intersection between this set and another set.
*
* @param that the set to intersect with.
* @return a new set consisting of all elements that are both in this
* set and in the given set `that`.
*/
def intersect(that: Set[A]): This = filter(that.contains)
/** Computes the intersection between this set and another set.
*
* @param that the set to intersect with.
* @return a new set consisting of all elements that are both in this
* set and in the given set `that`.
* @note Same as `intersect`.
*/
def &(that: Set[A]): This = intersect(that)
/** This method is an alias for `intersect`.
* It computes an intersection with set `that`.
* It removes all the elements that are not present in `that`.
*
* @param that the set to intersect with
*/
@deprecated("use & instead") def ** (that: Set[A]): This = intersect(that)
/** Computes the union between of set and another set.
*
* @param that the set to form the union with.
* @return a new set consisting of all elements that are in this
* set or in the given set `that`.
*/
def union(that: Set[A]): This = this.++(that)
/** Computes the union between this set and another set.
*
* @param that the set to form the union with.
* @return a new set consisting of all elements that are in this
* set or in the given set `that`.
* @note Same as `union`.
*/
def | (that: Set[A]): This = union(that)
/** Computes the difference of this set and another set.
*
* @param that the set of elements to exclude.
* @return a set containing those elements of this
* set that are not also contained in the given set `that`.
*/
def diff(that: Set[A]): This = --(that)
/** The difference of this set and another set.
*
* @param that the set of elements to exclude.
* @return a set containing those elements of this
* set that are not also contained in the given set `that`.
* @note Same as `diff`.
*/
def &~(that: Set[A]): This = diff(that)
/** Tests whether this set is a subset of another set.
*
* @param that the set to test.
* @return `true` if this set is a subset of `that`, i.e. if
* every element of this set is also an element of `that`.
*/
def subsetOf(that: Set[A]): Boolean = forall(that.contains)
/** Defines the prefix of this object's `toString` representation.
* @return a string representation which starts the result of `toString` applied to this set.
* Unless overridden this is simply `"Set"`.
*/
override def stringPrefix: String = "Set"
override def toString = super[IterableLike].toString
override def hashCode() = this map (_.hashCode) sum
/** Compares this set with another object for equality.
*
* @param that the other object
* @return `true` if `that` is a set which contains the same elements
* as this set.
* @note This operation contains an unchecked cast: if `that`
* is a set, it will assume with an unchecked cast
* that it has the same element type as this set.
* Any subsequuent ClassCastException is treated as a `false` result.
*/
override def equals(that: Any): Boolean = that match {
case that: Set[_] =>
(this eq that) ||
(that canEqual this) &&
(this.size == that.size) &&
(try this subsetOf that.asInstanceOf[Set[A]]
catch { case ex: ClassCastException => false })
case _ =>
false
}
}
|