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22 <li><a class=active href="#">Scala</a>
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24 </div>
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25
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26 <article>
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27 <h2>Scala mode</h2>
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28 <form>
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29 <textarea id="code" name="code">
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30
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31 /* __ *\
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32 ** ________ ___ / / ___ Scala API **
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33 ** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL **
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34 ** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
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35 ** /____/\___/_/ |_/____/_/ | | **
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36 ** |/ **
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37 \* */
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38
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39 package scala.collection
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40
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41 import generic._
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42 import mutable.{ Builder, ListBuffer }
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43 import annotation.{tailrec, migration, bridge}
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44 import annotation.unchecked.{ uncheckedVariance => uV }
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45 import parallel.ParIterable
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46
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47 /** A template trait for traversable collections of type `Traversable[A]`.
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48 *
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49 * $traversableInfo
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50 * @define mutability
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51 * @define traversableInfo
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52 * This is a base trait of all kinds of $mutability Scala collections. It
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53 * implements the behavior common to all collections, in terms of a method
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54 * `foreach` with signature:
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55 * {{{
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56 * def foreach[U](f: Elem => U): Unit
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57 * }}}
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58 * Collection classes mixing in this trait provide a concrete
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59 * `foreach` method which traverses all the
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60 * elements contained in the collection, applying a given function to each.
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61 * They also need to provide a method `newBuilder`
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62 * which creates a builder for collections of the same kind.
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63 *
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64 * A traversable class might or might not have two properties: strictness
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65 * and orderedness. Neither is represented as a type.
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66 *
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67 * The instances of a strict collection class have all their elements
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68 * computed before they can be used as values. By contrast, instances of
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69 * a non-strict collection class may defer computation of some of their
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70 * elements until after the instance is available as a value.
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71 * A typical example of a non-strict collection class is a
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72 * <a href="../immutable/Stream.html" target="ContentFrame">
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73 * `scala.collection.immutable.Stream`</a>.
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74 * A more general class of examples are `TraversableViews`.
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75 *
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76 * If a collection is an instance of an ordered collection class, traversing
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77 * its elements with `foreach` will always visit elements in the
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78 * same order, even for different runs of the program. If the class is not
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79 * ordered, `foreach` can visit elements in different orders for
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80 * different runs (but it will keep the same order in the same run).'
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81 *
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82 * A typical example of a collection class which is not ordered is a
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83 * `HashMap` of objects. The traversal order for hash maps will
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84 * depend on the hash codes of its elements, and these hash codes might
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85 * differ from one run to the next. By contrast, a `LinkedHashMap`
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86 * is ordered because it's `foreach` method visits elements in the
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87 * order they were inserted into the `HashMap`.
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88 *
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89 * @author Martin Odersky
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90 * @version 2.8
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91 * @since 2.8
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92 * @tparam A the element type of the collection
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93 * @tparam Repr the type of the actual collection containing the elements.
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94 *
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95 * @define Coll Traversable
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96 * @define coll traversable collection
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97 */
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98 trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr]
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99 with FilterMonadic[A, Repr]
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100 with TraversableOnce[A]
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101 with GenTraversableLike[A, Repr]
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102 with Parallelizable[A, ParIterable[A]]
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103 {
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104 self =>
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105
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106 import Traversable.breaks._
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107
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108 /** The type implementing this traversable */
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109 protected type Self = Repr
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110
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111 /** The collection of type $coll underlying this `TraversableLike` object.
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112 * By default this is implemented as the `TraversableLike` object itself,
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113 * but this can be overridden.
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114 */
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115 def repr: Repr = this.asInstanceOf[Repr]
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116
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117 /** The underlying collection seen as an instance of `$Coll`.
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118 * By default this is implemented as the current collection object itself,
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119 * but this can be overridden.
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120 */
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121 protected[this] def thisCollection: Traversable[A] = this.asInstanceOf[Traversable[A]]
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122
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123 /** A conversion from collections of type `Repr` to `$Coll` objects.
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124 * By default this is implemented as just a cast, but this can be overridden.
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125 */
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126 protected[this] def toCollection(repr: Repr): Traversable[A] = repr.asInstanceOf[Traversable[A]]
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127
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128 /** Creates a new builder for this collection type.
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129 */
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130 protected[this] def newBuilder: Builder[A, Repr]
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131
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132 protected[this] def parCombiner = ParIterable.newCombiner[A]
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133
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134 /** Applies a function `f` to all elements of this $coll.
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135 *
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136 * Note: this method underlies the implementation of most other bulk operations.
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137 * It's important to implement this method in an efficient way.
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138 *
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139 *
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140 * @param f the function that is applied for its side-effect to every element.
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141 * The result of function `f` is discarded.
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142 *
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143 * @tparam U the type parameter describing the result of function `f`.
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144 * This result will always be ignored. Typically `U` is `Unit`,
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145 * but this is not necessary.
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146 *
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147 * @usecase def foreach(f: A => Unit): Unit
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148 */
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149 def foreach[U](f: A => U): Unit
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150
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151 /** Tests whether this $coll is empty.
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152 *
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153 * @return `true` if the $coll contain no elements, `false` otherwise.
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154 */
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155 def isEmpty: Boolean = {
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156 var result = true
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157 breakable {
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158 for (x <- this) {
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159 result = false
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160 break
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161 }
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162 }
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163 result
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164 }
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165
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166 /** Tests whether this $coll is known to have a finite size.
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167 * All strict collections are known to have finite size. For a non-strict collection
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168 * such as `Stream`, the predicate returns `true` if all elements have been computed.
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169 * It returns `false` if the stream is not yet evaluated to the end.
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170 *
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171 * Note: many collection methods will not work on collections of infinite sizes.
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172 *
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173 * @return `true` if this collection is known to have finite size, `false` otherwise.
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174 */
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175 def hasDefiniteSize = true
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176
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177 def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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178 val b = bf(repr)
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179 if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.seq.size)
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180 b ++= thisCollection
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181 b ++= that.seq
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182 b.result
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183 }
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184
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185 @bridge
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186 def ++[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
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187 ++(that: GenTraversableOnce[B])(bf)
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188
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189 /** Concatenates this $coll with the elements of a traversable collection.
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190 * It differs from ++ in that the right operand determines the type of the
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191 * resulting collection rather than the left one.
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192 *
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193 * @param that the traversable to append.
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194 * @tparam B the element type of the returned collection.
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195 * @tparam That $thatinfo
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196 * @param bf $bfinfo
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197 * @return a new collection of type `That` which contains all elements
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198 * of this $coll followed by all elements of `that`.
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199 *
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200 * @usecase def ++:[B](that: TraversableOnce[B]): $Coll[B]
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201 *
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202 * @return a new $coll which contains all elements of this $coll
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203 * followed by all elements of `that`.
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204 */
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205 def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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206 val b = bf(repr)
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207 if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.size)
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208 b ++= that
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209 b ++= thisCollection
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210 b.result
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211 }
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212
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213 /** This overload exists because: for the implementation of ++: we should reuse
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214 * that of ++ because many collections override it with more efficient versions.
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215 * Since TraversableOnce has no '++' method, we have to implement that directly,
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216 * but Traversable and down can use the overload.
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217 */
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218 def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
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219 (that ++ seq)(breakOut)
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220
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221 def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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222 val b = bf(repr)
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223 b.sizeHint(this)
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224 for (x <- this) b += f(x)
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225 b.result
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226 }
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227
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228 def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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229 val b = bf(repr)
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230 for (x <- this) b ++= f(x).seq
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231 b.result
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232 }
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233
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234 /** Selects all elements of this $coll which satisfy a predicate.
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235 *
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236 * @param p the predicate used to test elements.
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237 * @return a new $coll consisting of all elements of this $coll that satisfy the given
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238 * predicate `p`. The order of the elements is preserved.
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239 */
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240 def filter(p: A => Boolean): Repr = {
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241 val b = newBuilder
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242 for (x <- this)
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243 if (p(x)) b += x
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244 b.result
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245 }
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246
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247 /** Selects all elements of this $coll which do not satisfy a predicate.
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248 *
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249 * @param p the predicate used to test elements.
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250 * @return a new $coll consisting of all elements of this $coll that do not satisfy the given
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251 * predicate `p`. The order of the elements is preserved.
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252 */
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253 def filterNot(p: A => Boolean): Repr = filter(!p(_))
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254
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255 def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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256 val b = bf(repr)
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257 for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
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258 b.result
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259 }
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260
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261 /** Builds a new collection by applying an option-valued function to all
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262 * elements of this $coll on which the function is defined.
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263 *
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264 * @param f the option-valued function which filters and maps the $coll.
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265 * @tparam B the element type of the returned collection.
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266 * @tparam That $thatinfo
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267 * @param bf $bfinfo
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268 * @return a new collection of type `That` resulting from applying the option-valued function
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269 * `f` to each element and collecting all defined results.
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270 * The order of the elements is preserved.
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271 *
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272 * @usecase def filterMap[B](f: A => Option[B]): $Coll[B]
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273 *
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274 * @param pf the partial function which filters and maps the $coll.
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275 * @return a new $coll resulting from applying the given option-valued function
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276 * `f` to each element and collecting all defined results.
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277 * The order of the elements is preserved.
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278 def filterMap[B, That](f: A => Option[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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279 val b = bf(repr)
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280 for (x <- this)
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281 f(x) match {
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282 case Some(y) => b += y
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283 case _ =>
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284 }
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285 b.result
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286 }
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287 */
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288
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289 /** Partitions this $coll in two ${coll}s according to a predicate.
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290 *
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291 * @param p the predicate on which to partition.
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292 * @return a pair of ${coll}s: the first $coll consists of all elements that
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293 * satisfy the predicate `p` and the second $coll consists of all elements
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294 * that don't. The relative order of the elements in the resulting ${coll}s
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295 * is the same as in the original $coll.
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296 */
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297 def partition(p: A => Boolean): (Repr, Repr) = {
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298 val l, r = newBuilder
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299 for (x <- this) (if (p(x)) l else r) += x
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300 (l.result, r.result)
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301 }
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302
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303 def groupBy[K](f: A => K): immutable.Map[K, Repr] = {
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304 val m = mutable.Map.empty[K, Builder[A, Repr]]
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305 for (elem <- this) {
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306 val key = f(elem)
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307 val bldr = m.getOrElseUpdate(key, newBuilder)
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308 bldr += elem
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309 }
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310 val b = immutable.Map.newBuilder[K, Repr]
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311 for ((k, v) <- m)
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312 b += ((k, v.result))
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313
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314 b.result
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315 }
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316
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317 /** Tests whether a predicate holds for all elements of this $coll.
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318 *
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319 * $mayNotTerminateInf
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320 *
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321 * @param p the predicate used to test elements.
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322 * @return `true` if the given predicate `p` holds for all elements
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323 * of this $coll, otherwise `false`.
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324 */
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325 def forall(p: A => Boolean): Boolean = {
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326 var result = true
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327 breakable {
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328 for (x <- this)
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329 if (!p(x)) { result = false; break }
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330 }
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331 result
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332 }
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333
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334 /** Tests whether a predicate holds for some of the elements of this $coll.
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335 *
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336 * $mayNotTerminateInf
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337 *
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338 * @param p the predicate used to test elements.
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339 * @return `true` if the given predicate `p` holds for some of the
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340 * elements of this $coll, otherwise `false`.
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341 */
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342 def exists(p: A => Boolean): Boolean = {
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343 var result = false
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344 breakable {
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345 for (x <- this)
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346 if (p(x)) { result = true; break }
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347 }
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348 result
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349 }
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350
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351 /** Finds the first element of the $coll satisfying a predicate, if any.
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352 *
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353 * $mayNotTerminateInf
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354 * $orderDependent
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355 *
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356 * @param p the predicate used to test elements.
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357 * @return an option value containing the first element in the $coll
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358 * that satisfies `p`, or `None` if none exists.
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359 */
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360 def find(p: A => Boolean): Option[A] = {
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361 var result: Option[A] = None
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362 breakable {
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363 for (x <- this)
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364 if (p(x)) { result = Some(x); break }
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365 }
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366 result
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367 }
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368
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369 def scan[B >: A, That](z: B)(op: (B, B) => B)(implicit cbf: CanBuildFrom[Repr, B, That]): That = scanLeft(z)(op)
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370
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371 def scanLeft[B, That](z: B)(op: (B, A) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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372 val b = bf(repr)
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373 b.sizeHint(this, 1)
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374 var acc = z
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375 b += acc
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376 for (x <- this) { acc = op(acc, x); b += acc }
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377 b.result
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378 }
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379
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380 @migration(2, 9,
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381 "This scanRight definition has changed in 2.9.\n" +
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382 "The previous behavior can be reproduced with scanRight.reverse."
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383 )
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384 def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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385 var scanned = List(z)
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386 var acc = z
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387 for (x <- reversed) {
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388 acc = op(x, acc)
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389 scanned ::= acc
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390 }
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391 val b = bf(repr)
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392 for (elem <- scanned) b += elem
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393 b.result
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394 }
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395
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396 /** Selects the first element of this $coll.
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397 * $orderDependent
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398 * @return the first element of this $coll.
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399 * @throws `NoSuchElementException` if the $coll is empty.
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400 */
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401 def head: A = {
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402 var result: () => A = () => throw new NoSuchElementException
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403 breakable {
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404 for (x <- this) {
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405 result = () => x
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406 break
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407 }
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408 }
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409 result()
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410 }
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411
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412 /** Optionally selects the first element.
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413 * $orderDependent
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414 * @return the first element of this $coll if it is nonempty, `None` if it is empty.
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415 */
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416 def headOption: Option[A] = if (isEmpty) None else Some(head)
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417
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418 /** Selects all elements except the first.
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419 * $orderDependent
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420 * @return a $coll consisting of all elements of this $coll
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421 * except the first one.
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422 * @throws `UnsupportedOperationException` if the $coll is empty.
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423 */
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424 override def tail: Repr = {
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425 if (isEmpty) throw new UnsupportedOperationException("empty.tail")
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426 drop(1)
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427 }
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428
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429 /** Selects the last element.
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430 * $orderDependent
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431 * @return The last element of this $coll.
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432 * @throws NoSuchElementException If the $coll is empty.
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433 */
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434 def last: A = {
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435 var lst = head
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436 for (x <- this)
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437 lst = x
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438 lst
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439 }
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440
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441 /** Optionally selects the last element.
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442 * $orderDependent
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443 * @return the last element of this $coll$ if it is nonempty, `None` if it is empty.
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444 */
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445 def lastOption: Option[A] = if (isEmpty) None else Some(last)
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446
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447 /** Selects all elements except the last.
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448 * $orderDependent
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449 * @return a $coll consisting of all elements of this $coll
|
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450 * except the last one.
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451 * @throws `UnsupportedOperationException` if the $coll is empty.
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452 */
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453 def init: Repr = {
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454 if (isEmpty) throw new UnsupportedOperationException("empty.init")
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455 var lst = head
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456 var follow = false
|
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457 val b = newBuilder
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458 b.sizeHint(this, -1)
|
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459 for (x <- this.seq) {
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460 if (follow) b += lst
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461 else follow = true
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462 lst = x
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463 }
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464 b.result
|
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465 }
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466
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467 def take(n: Int): Repr = slice(0, n)
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468
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469 def drop(n: Int): Repr =
|
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470 if (n <= 0) {
|
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471 val b = newBuilder
|
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472 b.sizeHint(this)
|
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|
473 b ++= thisCollection result
|
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|
474 }
|
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|
475 else sliceWithKnownDelta(n, Int.MaxValue, -n)
|
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|
476
|
|
|
477 def slice(from: Int, until: Int): Repr = sliceWithKnownBound(math.max(from, 0), until)
|
|
|
478
|
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|
479 // Precondition: from >= 0, until > 0, builder already configured for building.
|
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|
480 private[this] def sliceInternal(from: Int, until: Int, b: Builder[A, Repr]): Repr = {
|
|
|
481 var i = 0
|
|
|
482 breakable {
|
|
|
483 for (x <- this.seq) {
|
|
|
484 if (i >= from) b += x
|
|
|
485 i += 1
|
|
|
486 if (i >= until) break
|
|
|
487 }
|
|
|
488 }
|
|
|
489 b.result
|
|
|
490 }
|
|
|
491 // Precondition: from >= 0
|
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|
492 private[scala] def sliceWithKnownDelta(from: Int, until: Int, delta: Int): Repr = {
|
|
|
493 val b = newBuilder
|
|
|
494 if (until <= from) b.result
|
|
|
495 else {
|
|
|
496 b.sizeHint(this, delta)
|
|
|
497 sliceInternal(from, until, b)
|
|
|
498 }
|
|
|
499 }
|
|
|
500 // Precondition: from >= 0
|
|
|
501 private[scala] def sliceWithKnownBound(from: Int, until: Int): Repr = {
|
|
|
502 val b = newBuilder
|
|
|
503 if (until <= from) b.result
|
|
|
504 else {
|
|
|
505 b.sizeHintBounded(until - from, this)
|
|
|
506 sliceInternal(from, until, b)
|
|
|
507 }
|
|
|
508 }
|
|
|
509
|
|
|
510 def takeWhile(p: A => Boolean): Repr = {
|
|
|
511 val b = newBuilder
|
|
|
512 breakable {
|
|
|
513 for (x <- this) {
|
|
|
514 if (!p(x)) break
|
|
|
515 b += x
|
|
|
516 }
|
|
|
517 }
|
|
|
518 b.result
|
|
|
519 }
|
|
|
520
|
|
|
521 def dropWhile(p: A => Boolean): Repr = {
|
|
|
522 val b = newBuilder
|
|
|
523 var go = false
|
|
|
524 for (x <- this) {
|
|
|
525 if (!p(x)) go = true
|
|
|
526 if (go) b += x
|
|
|
527 }
|
|
|
528 b.result
|
|
|
529 }
|
|
|
530
|
|
|
531 def span(p: A => Boolean): (Repr, Repr) = {
|
|
|
532 val l, r = newBuilder
|
|
|
533 var toLeft = true
|
|
|
534 for (x <- this) {
|
|
|
535 toLeft = toLeft && p(x)
|
|
|
536 (if (toLeft) l else r) += x
|
|
|
537 }
|
|
|
538 (l.result, r.result)
|
|
|
539 }
|
|
|
540
|
|
|
541 def splitAt(n: Int): (Repr, Repr) = {
|
|
|
542 val l, r = newBuilder
|
|
|
543 l.sizeHintBounded(n, this)
|
|
|
544 if (n >= 0) r.sizeHint(this, -n)
|
|
|
545 var i = 0
|
|
|
546 for (x <- this) {
|
|
|
547 (if (i < n) l else r) += x
|
|
|
548 i += 1
|
|
|
549 }
|
|
|
550 (l.result, r.result)
|
|
|
551 }
|
|
|
552
|
|
|
553 /** Iterates over the tails of this $coll. The first value will be this
|
|
|
554 * $coll and the final one will be an empty $coll, with the intervening
|
|
|
555 * values the results of successive applications of `tail`.
|
|
|
556 *
|
|
|
557 * @return an iterator over all the tails of this $coll
|
|
|
558 * @example `List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)`
|
|
|
559 */
|
|
|
560 def tails: Iterator[Repr] = iterateUntilEmpty(_.tail)
|
|
|
561
|
|
|
562 /** Iterates over the inits of this $coll. The first value will be this
|
|
|
563 * $coll and the final one will be an empty $coll, with the intervening
|
|
|
564 * values the results of successive applications of `init`.
|
|
|
565 *
|
|
|
566 * @return an iterator over all the inits of this $coll
|
|
|
567 * @example `List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)`
|
|
|
568 */
|
|
|
569 def inits: Iterator[Repr] = iterateUntilEmpty(_.init)
|
|
|
570
|
|
|
571 /** Copies elements of this $coll to an array.
|
|
|
572 * Fills the given array `xs` with at most `len` elements of
|
|
|
573 * this $coll, starting at position `start`.
|
|
|
574 * Copying will stop once either the end of the current $coll is reached,
|
|
|
575 * or the end of the array is reached, or `len` elements have been copied.
|
|
|
576 *
|
|
|
577 * $willNotTerminateInf
|
|
|
578 *
|
|
|
579 * @param xs the array to fill.
|
|
|
580 * @param start the starting index.
|
|
|
581 * @param len the maximal number of elements to copy.
|
|
|
582 * @tparam B the type of the elements of the array.
|
|
|
583 *
|
|
|
584 *
|
|
|
585 * @usecase def copyToArray(xs: Array[A], start: Int, len: Int): Unit
|
|
|
586 */
|
|
|
587 def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
|
|
|
588 var i = start
|
|
|
589 val end = (start + len) min xs.length
|
|
|
590 breakable {
|
|
|
591 for (x <- this) {
|
|
|
592 if (i >= end) break
|
|
|
593 xs(i) = x
|
|
|
594 i += 1
|
|
|
595 }
|
|
|
596 }
|
|
|
597 }
|
|
|
598
|
|
|
599 def toTraversable: Traversable[A] = thisCollection
|
|
|
600 def toIterator: Iterator[A] = toStream.iterator
|
|
|
601 def toStream: Stream[A] = toBuffer.toStream
|
|
|
602
|
|
|
603 /** Converts this $coll to a string.
|
|
|
604 *
|
|
|
605 * @return a string representation of this collection. By default this
|
|
|
606 * string consists of the `stringPrefix` of this $coll,
|
|
|
607 * followed by all elements separated by commas and enclosed in parentheses.
|
|
|
608 */
|
|
|
609 override def toString = mkString(stringPrefix + "(", ", ", ")")
|
|
|
610
|
|
|
611 /** Defines the prefix of this object's `toString` representation.
|
|
|
612 *
|
|
|
613 * @return a string representation which starts the result of `toString`
|
|
|
614 * applied to this $coll. By default the string prefix is the
|
|
|
615 * simple name of the collection class $coll.
|
|
|
616 */
|
|
|
617 def stringPrefix : String = {
|
|
|
618 var string = repr.asInstanceOf[AnyRef].getClass.getName
|
|
|
619 val idx1 = string.lastIndexOf('.' : Int)
|
|
|
620 if (idx1 != -1) string = string.substring(idx1 + 1)
|
|
|
621 val idx2 = string.indexOf('$')
|
|
|
622 if (idx2 != -1) string = string.substring(0, idx2)
|
|
|
623 string
|
|
|
624 }
|
|
|
625
|
|
|
626 /** Creates a non-strict view of this $coll.
|
|
|
627 *
|
|
|
628 * @return a non-strict view of this $coll.
|
|
|
629 */
|
|
|
630 def view = new TraversableView[A, Repr] {
|
|
|
631 protected lazy val underlying = self.repr
|
|
|
632 override def foreach[U](f: A => U) = self foreach f
|
|
|
633 }
|
|
|
634
|
|
|
635 /** Creates a non-strict view of a slice of this $coll.
|
|
|
636 *
|
|
|
637 * Note: the difference between `view` and `slice` is that `view` produces
|
|
|
638 * a view of the current $coll, whereas `slice` produces a new $coll.
|
|
|
639 *
|
|
|
640 * Note: `view(from, to)` is equivalent to `view.slice(from, to)`
|
|
|
641 * $orderDependent
|
|
|
642 *
|
|
|
643 * @param from the index of the first element of the view
|
|
|
644 * @param until the index of the element following the view
|
|
|
645 * @return a non-strict view of a slice of this $coll, starting at index `from`
|
|
|
646 * and extending up to (but not including) index `until`.
|
|
|
647 */
|
|
|
648 def view(from: Int, until: Int): TraversableView[A, Repr] = view.slice(from, until)
|
|
|
649
|
|
|
650 /** Creates a non-strict filter of this $coll.
|
|
|
651 *
|
|
|
652 * Note: the difference between `c filter p` and `c withFilter p` is that
|
|
|
653 * the former creates a new collection, whereas the latter only
|
|
|
654 * restricts the domain of subsequent `map`, `flatMap`, `foreach`,
|
|
|
655 * and `withFilter` operations.
|
|
|
656 * $orderDependent
|
|
|
657 *
|
|
|
658 * @param p the predicate used to test elements.
|
|
|
659 * @return an object of class `WithFilter`, which supports
|
|
|
660 * `map`, `flatMap`, `foreach`, and `withFilter` operations.
|
|
|
661 * All these operations apply to those elements of this $coll which
|
|
|
662 * satisfy the predicate `p`.
|
|
|
663 */
|
|
|
664 def withFilter(p: A => Boolean): FilterMonadic[A, Repr] = new WithFilter(p)
|
|
|
665
|
|
|
666 /** A class supporting filtered operations. Instances of this class are
|
|
|
667 * returned by method `withFilter`.
|
|
|
668 */
|
|
|
669 class WithFilter(p: A => Boolean) extends FilterMonadic[A, Repr] {
|
|
|
670
|
|
|
671 /** Builds a new collection by applying a function to all elements of the
|
|
|
672 * outer $coll containing this `WithFilter` instance that satisfy predicate `p`.
|
|
|
673 *
|
|
|
674 * @param f the function to apply to each element.
|
|
|
675 * @tparam B the element type of the returned collection.
|
|
|
676 * @tparam That $thatinfo
|
|
|
677 * @param bf $bfinfo
|
|
|
678 * @return a new collection of type `That` resulting from applying
|
|
|
679 * the given function `f` to each element of the outer $coll
|
|
|
680 * that satisfies predicate `p` and collecting the results.
|
|
|
681 *
|
|
|
682 * @usecase def map[B](f: A => B): $Coll[B]
|
|
|
683 *
|
|
|
684 * @return a new $coll resulting from applying the given function
|
|
|
685 * `f` to each element of the outer $coll that satisfies
|
|
|
686 * predicate `p` and collecting the results.
|
|
|
687 */
|
|
|
688 def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
|
|
|
689 val b = bf(repr)
|
|
|
690 for (x <- self)
|
|
|
691 if (p(x)) b += f(x)
|
|
|
692 b.result
|
|
|
693 }
|
|
|
694
|
|
|
695 /** Builds a new collection by applying a function to all elements of the
|
|
|
696 * outer $coll containing this `WithFilter` instance that satisfy
|
|
|
697 * predicate `p` and concatenating the results.
|
|
|
698 *
|
|
|
699 * @param f the function to apply to each element.
|
|
|
700 * @tparam B the element type of the returned collection.
|
|
|
701 * @tparam That $thatinfo
|
|
|
702 * @param bf $bfinfo
|
|
|
703 * @return a new collection of type `That` resulting from applying
|
|
|
704 * the given collection-valued function `f` to each element
|
|
|
705 * of the outer $coll that satisfies predicate `p` and
|
|
|
706 * concatenating the results.
|
|
|
707 *
|
|
|
708 * @usecase def flatMap[B](f: A => TraversableOnce[B]): $Coll[B]
|
|
|
709 *
|
|
|
710 * @return a new $coll resulting from applying the given collection-valued function
|
|
|
711 * `f` to each element of the outer $coll that satisfies predicate `p` and concatenating the results.
|
|
|
712 */
|
|
|
713 def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
|
|
|
714 val b = bf(repr)
|
|
|
715 for (x <- self)
|
|
|
716 if (p(x)) b ++= f(x).seq
|
|
|
717 b.result
|
|
|
718 }
|
|
|
719
|
|
|
720 /** Applies a function `f` to all elements of the outer $coll containing
|
|
|
721 * this `WithFilter` instance that satisfy predicate `p`.
|
|
|
722 *
|
|
|
723 * @param f the function that is applied for its side-effect to every element.
|
|
|
724 * The result of function `f` is discarded.
|
|
|
725 *
|
|
|
726 * @tparam U the type parameter describing the result of function `f`.
|
|
|
727 * This result will always be ignored. Typically `U` is `Unit`,
|
|
|
728 * but this is not necessary.
|
|
|
729 *
|
|
|
730 * @usecase def foreach(f: A => Unit): Unit
|
|
|
731 */
|
|
|
732 def foreach[U](f: A => U): Unit =
|
|
|
733 for (x <- self)
|
|
|
734 if (p(x)) f(x)
|
|
|
735
|
|
|
736 /** Further refines the filter for this $coll.
|
|
|
737 *
|
|
|
738 * @param q the predicate used to test elements.
|
|
|
739 * @return an object of class `WithFilter`, which supports
|
|
|
740 * `map`, `flatMap`, `foreach`, and `withFilter` operations.
|
|
|
741 * All these operations apply to those elements of this $coll which
|
|
|
742 * satisfy the predicate `q` in addition to the predicate `p`.
|
|
|
743 */
|
|
|
744 def withFilter(q: A => Boolean): WithFilter =
|
|
|
745 new WithFilter(x => p(x) && q(x))
|
|
|
746 }
|
|
|
747
|
|
|
748 // A helper for tails and inits.
|
|
|
749 private def iterateUntilEmpty(f: Traversable[A @uV] => Traversable[A @uV]): Iterator[Repr] = {
|
|
|
750 val it = Iterator.iterate(thisCollection)(f) takeWhile (x => !x.isEmpty)
|
|
|
751 it ++ Iterator(Nil) map (newBuilder ++= _ result)
|
|
|
752 }
|
|
|
753 }
|
|
|
754
|
|
|
755
|
|
|
756 </textarea>
|
|
|
757 </form>
|
|
|
758
|
|
|
759 <script>
|
|
|
760 var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
|
|
|
761 lineNumbers: true,
|
|
|
762 matchBrackets: true,
|
|
|
763 theme: "ambiance",
|
|
|
764 mode: "text/x-scala"
|
|
|
765 });
|
|
|
766 </script>
|
|
|
767 </article>
|
