【scala初学】 Seq sequence IndexedSeq and LinearSeq

在sequences上操作，如下表，分为几种：

Indexing and length 

方法：<code>apply</code>, <code>isDefinedAt</code>, <code>length</code>, <code>indices</code>, and<code>lengthCompare</code>

   apply方法用于建立索引，因此类型Seq[T]的一个序列是一个partial函数，他获取一个int参数，并且产生了一个类型T的序列。综上，Seq[T]扩展了 <code>PartialFunction[Int, T]。</code>

<code>   <code>lengthCompare</code> </code>允许比较两个sequences序列的长度，甚至有一个可以是无限大

Index search operations

方法：<code>indexOf</code>, <code>lastIndexOf</code>, <code>indexOfSlice</code>, <code>lastIndexOfSlice</code>,<code>indexWhere</code>, <code>lastIndexWhere</code>, 

<code>segmentLength</code>, <code>prefixLength</code>返回索引或者匹配一些断言

Addition operations

方法：<code>+:</code>, <code>:+</code>, <code>padTo</code>

返回一些新的序列，通过头尾增加元素

Update operations

方法：<code>updated</code>, <code>patch</code>

返回一个新的序列，通过更新

Sorting operations

方法：<code>sorted</code>, <code>sortWith</code>, <code>sortBy</code>,

排序，根据多个标准

reversal operations

方法：<code>reverse</code>, <code>reverseIterator</code>, <code>reverseMap</code>

倒序产生或者处理一个序列

Comparisons

方法：<code>startsWith</code>, <code>endsWith</code>, <code>contains</code>, <code>containsSlice</code>, <code>corresponds</code>

比较连个元素或者在一个序列中查找一个元素

Multiset

方法：<code>intersect</code>, <code>diff</code>, <code>union</code>, <code>distinct</code>

在两个序列的元素上做类set的操作，或者移除重复值（这个估计是指单序列中）

  如果一个序列是可变的（mutable）,会提供一个额外的方法，update(书生：区别updated)，它能让序列的元素更新。正如在Scala中，语法如seq(idx)=elem 仅仅是seq.update(idx,elem)的一个简写，可以说update给予了一些语法上的便利。

updates: 返回一个被修改后的新的序列代替原序列,对所有序列有效。

update: 修改序列中的元素， 只对可变mutable序列有效

Class Seq 函数

序列

WHAT IT IS

WHAT IT DOES

Indexing and Length:

<code>xs(i)</code>

(or, written out, <code>xs apply i</code>). The element of <code>xs</code> at index <code>i</code>.

<code>xs isDefinedAt i</code>

Tests whether <code>i</code> is contained in <code>xs.indices</code>.

<code>xs.length</code>

The length of the sequence (same as <code>size</code>).

<code>xs.lengthCompare ys</code>

Returns <code>-1</code> if <code>xs</code> is shorter than <code>ys</code>, <code>+1</code> if it is longer, and <code>0</code> is they have the same length. Works even if one if the sequences is infinite.

<code>xs.indices</code>

The index range of <code>xs</code>, extending from <code>0</code> to <code>xs.length - 1</code>.

Index Search:

<code>xs indexOf x</code>

The index of the first element in <code>xs</code> equal to <code>x</code> (several variants exist).

<code>xs lastIndexOf x</code>

The index of the last element in <code>xs</code> equal to <code>x</code> (several variants exist).

<code>xs indexOfSlice ys</code>

The first index of <code>xs</code> such that successive elements starting from that index form the sequence <code>ys</code>.

<code>xs lastIndexOfSlice ys</code>

The last index of <code>xs</code> such that successive elements starting from that index form the sequence <code>ys</code>.

<code>xs indexWhere p</code>

The index of the first element in xs that satisfies <code>p</code> (several variants exist).

<code>xs segmentLength (p, i)</code>

The length of the longest uninterrupted segment of elements in <code>xs</code>, starting with <code>xs(i)</code>, that all satisfy the predicate <code>p</code>.

<code>xs prefixLength p</code>

The length of the longest prefix of elements in <code>xs</code> that all satisfy the predicate <code>p</code>.

Additions:

<code>x +: xs</code>

A new sequence that consists of <code>x</code> prepended to <code>xs</code>.

<code>xs :+ x</code>

A new sequence that consists of <code>x</code> appended to <code>xs</code>.

<code>xs padTo (len, x)</code>

The sequence resulting from appending the value <code>x</code> to <code>xs</code> until length <code>len</code> is reached.

Updates:

<code>xs patch (i, ys, r)</code>

The sequence resulting from replacing <code>r</code> elements of <code>xs</code> starting with <code>i</code> by the patch <code>ys</code>.

<code>xs updated (i, x)</code>

A copy of <code>xs</code> with the element at index <code>i</code> replaced by <code>x</code>.

<code>xs(i) = x</code>

(or, written out, <code>xs.update(i, x)</code>, only available for <code>mutable.Seq</code>s). Changes the element of <code>xs</code> at index <code>i</code> to <code>x</code>.

Sorting:

<code>xs.sorted</code>

A new sequence obtained by sorting the elements of <code>xs</code> using the standard ordering of the element type of <code>xs</code>.

<code>xs sortWith lt</code>

A new sequence obtained by sorting the elements of <code>xs</code> using <code>lt</code> as comparison operation.

<code>xs sortBy f</code>

A new sequence obtained by sorting the elements of <code>xs</code>. Comparison between two elements proceeds by mapping the function <code>f</code> over both and comparing the results.

Reversals:

<code>xs.reverse</code>

A sequence with the elements of <code>xs</code> in reverse order.

<code>xs.reverseIterator</code>

An iterator yielding all the elements of <code>xs</code> in reverse order.

<code>xs reverseMap f</code>

A sequence obtained by mapping <code>f</code> over the elements of <code>xs</code> in reverse order.

Comparisons:

<code>xs startsWith ys</code>

Tests whether <code>xs</code> starts with sequence <code>ys</code> (several variants exist).

<code>xs endsWith ys</code>

Tests whether <code>xs</code> ends with sequence <code>ys</code> (several variants exist).

<code>xs contains x</code>

Tests whether <code>xs</code> has an element equal to <code>x</code>.

<code>xs containsSlice ys</code>

Tests whether <code>xs</code> has a contiguous subsequence equal to <code>ys</code>.

<code>(xs corresponds ys)(p)</code>

Tests whether corresponding elements of <code>xs</code> and <code>ys</code> satisfy the binary predicate <code>p</code>.

Multiset Operations:

<code>xs intersect ys</code>

The multi-set intersection of sequences <code>xs</code> and <code>ys</code> that preserves the order of elements in <code>xs</code>.

<code>xs diff ys</code>

The multi-set difference of sequences <code>xs</code> and <code>ys</code> that preserves the order of elements in <code>xs</code>.

<code>xs union ys</code>

Multiset union; same as <code>xs ++ ys</code>.

<code>xs.distinct</code>

A subsequence of <code>xs</code> that contains no duplicated element.

Vector提供了一个令人感兴趣的折中，在indexed和linear,他能有效的确保稳定的index和linear访问的时间总开销 。 因此，他是一个非常好的混合访问模式。

本文转自 wws5201985 51CTO博客，原文链接：http://blog.51cto.com/yjplxq/1432054，如需转载请自行联系原作者