Concept ForwardIterator

Concept ForwardIterator 前向迭代器概念

ForwardIterator 前向迭代器

Description 說明

A forward iterator is an iterator that can read through a sequence of values. It is multi-pass (old values of the iterator can be re-used), and can be either mutable (data pointed to by it can be changed) or not mutable.
前向迭代器是一種可以讀入一組值的序列的迭代器。它是多遍的(迭代器的舊值可以重用)，可以是可寫的(所指數據可以改變)或不可寫的。

An iterator represents a position in a sequence. Therefore, the iterator can point into the sequence (returning a value when dereferenced and being incrementable), or be off-the-end (and not dereferenceable or incrementable).
迭代器表示了在一個序列中的某個位置。因此，迭代器可以指向序列內部(在提領時返回一個值且可以遞增)，或者指向序列末端之後(不可提領且不可遞增)

Refinement of 精化自

Associated types 關聯類型

value_type
```
std::iterator_traits<Iter>::value_type
```
The value type of the iterator
迭代器的值類型
category
```
std::iterator_traits<Iter>::iterator_category
```
The category of the iterator
迭代器的類別

Notation 符號

Iter: A type playing the role of iterator-type in the ForwardIterator concept.cc 雙
i, j: Objects of type Iter; 類型 Iter 的對象
x: Object of type value_type; 類型 value_type 的對象

Type expressions 類型表達式

Category tag 類別標記: category must be derived from std::forward_iterator_tag.; category 必須派生自 std::forward_iterator_tag。

Valid expressions 有效表達式

Name 名字	Expression 表達式	Type 類型	Precondition 前置條件	Semantics 語義	Postcondition 後置條件
Dereference 提領	*i	const-if-not-mutable value_type &	`i` is incrementable (not off-the-end) `i` 是可遞增的(不是 off-the-end)
Member access 成員訪問	i->{member-name} (return type is pointer-to-object type)(返回類型為對像指針類型)	const-if-not-mutable value_type *	`i` is incrementable (not off-the-end) `i` 是可遞增的(不是 off-the-end)
Preincrement 前綴遞增	++i	Iter &	`i` is incrementable (not off-the-end) `i` 是可遞增的(不是 off-the-end)
Postincrement 後綴遞增	i++	Iter	`i` is incrementable (not off-the-end) `i` 是可遞增的(不是 off-the-end)	Equivalent to `{Iter j = i; ++i; return j;}` 等價於 `{Iter j = i; ++i; return j;}`	`i` is dereferenceable or off-the-end `i` 為可提領的或 off-the-end

Complexity 複雜度

All iterator operations must take amortized constant time.
迭代器的所有操作必須為分期常量時間複雜度。

Invariants 不變式

Predecrement must return object 前綴遞增必須返回對像: &i = &(++i)
Unique path through sequence 以唯一路徑遍歷序列: i == j implies ++i == ++j

Models 模型

T *
std::hash_set<T>::iterator