聲明為pair類型的變量可以有三種賦值方法：
1. 通過初始化賦值 直接聲明的時候 后面加括號并且數(shù)據(jù)，如下a
2. 通過.first .second 來賦值 如下b
3. 通過 = make_pair() 來賦值， 如下c
a. pair <string,double> product1 ("tomatoes",3.25);
pair <string,double> product2;
pair <string,double> product3;
b. product2.first = "lightbulbs"; // type of first is string
product2.second = 0.99; // type of second is double
c. product3 = make_pair ("shoes",20.0);
template <class T1, class T2> struct pair;
Pair of values
This class couples together a pair of values, which may be of different types (T1 and T2). The individual values can be accessed through the public members first and second.
The class is defined as:
1
2
3
4
5
6
7
8
9
10
11
12
|
template <class T1, class T2> struct pair
{
typedef T1 first_type;
typedef T2 second_type;
T1 first;
T2 second;
pair() : first(T1()), second(T2()) {}
pair(const T1& x, const T2& y) : first(x), second(y) {}
template <class U, class V>
pair (const pair<U,V> &p) : first(p.first), second(p.second) { }
}
|
Members
- first_type, second_type
- Alises of template parameters T1 and T2 respectively.
- first, second
- Data members containing the first and second values stored in the pair.
- pair()
- Constructs a pair object with each of its members first and second constructed with their respective default constructors.
- pair(const T1& x, const T2& y)
- Constructs a pair object with its members first and second initialized to x and y, respectively.
- template <class U, class V> pair (const pair<U,V> &p)
- Constructs a pair object with its members first and second initialized to the corresponding elements in p, which must be of any couple of implicitly-convertible types (including the same types).
-
Example
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
#include <iostream>
#include <utility>
#include <string>
using namespace std;
int main () {
pair <string,double> product1 ("tomatoes",3.25);
pair <string,double> product2;
pair <string,double> product3;
product2.first = "lightbulbs"; // type of first is string
product2.second = 0.99; // type of second is double
product3 = make_pair ("shoes",20.0);
cout << "The price of " << product1.first << " is $" << product1.second << "\n";
cout << "The price of " << product2.first << " is $" << product2.second << "\n";
cout << "The price of " << product3.first << " is $" << product3.second << "\n";
return 0;
}
|
Output:
The price of tomatoes is $3.25
The price of lightbulbs is $0.99
The price of shoes is $20 |
