Question

我的Char Source Scala计划遇到了麻烦。要开发的包实现了文档源的概念。文档源类似于迭代器但是以字符或单词形式生成其内容，以最方便的为基础应用。与迭代器一样，单词和字符“在运行中”生成并且不存储。正确文档源的实现应该能够

Trait CharSource：这个特性代表了我可以修改变换器混合的基本类型。它的来源人物是抽象的。从它衍生的单词和单词，字符。处理大型文档而不完全加载它们在记忆中。文档源提供两种方法： •chars：生成文档的内容作为字符的迭代器; •words：生成文档内容作为单词的迭代器。

这是我在迭代器上使用monaid运算符时遇到问题的地方。我尝试了foreach和map。

Class IteratorDocumentSource：

此类为我们提供了RichDocumentSource类型的默认实现。它可以用来混合在各种组合的特征和观察结果。请注意，此类实现完整（“丰富”）文档源接口，包括monadic运算符。

package document

class IteratorDocumentSource(iterator: Iterator[Char]) extends CharSource 
with RichDocumentSource {

protected def source: Iterator[Char] = iterator

def foreach[A](f: (Char) => A): Unit = {
 val it = iterator
 for( x <- it ) yield f(x)
 }

def map(f: (Char) => Char): IteratorDocumentSource = {
 val it = iterator
 val n  = for( x <- it ) yield f(x)
 }

new IteratorDocumentSource(n)

def flatMap(f: (Char) => TraversableOnce[Char]): IteratorDocumentSource = 
???

def withFilter(f: (Char) => Boolean): IteratorDocumentSource = ???
}




// $Id: RichDocumentSource.scala 93 2017-03-26 18:46:10Z abcdef $

package document

/** A rich document source.
* It extends a regular document source with the so-called "monadic" 
functions:
* `foreach`, `withFilter`, `map` and `flatMap`.  Those operate at the 
''character'' level, not on
 * words.
 *
 * @see Iterator

 trait RichDocumentSource extends DocumentSource {

 /** Applies the given function to all the characters in the document. */
 def foreach[A](f: (Char) => A): Unit

  /** A new document obtained by applying the given transformation to all 
  the 
 characters of this
 * document.
 */
 def map(f: (Char) => Char): RichDocumentSource

 /** A new document obtained by applying the given transformation to all the 
 characters of this
 * document.
 */
 def flatMap(f: (Char) => TraversableOnce[Char]): RichDocumentSource

 /** A new document obtained by applying the given filter to all the 
 characters of this document.
 */
 def withFilter(f: (Char) => Boolean): RichDocumentSource
  }

Scala Monad对迭代器的操作

0 个答案: