下面是关于ios 类的叙述,正确的是( )。 A. 它是istream 类和ostream 类的虚基类 B. 它只是istream 类的虚基类 C. 它只是ostream 类的虚基类 D. 它是iostrearm 类的虚基类
时间: 2024-04-02 21:32:05 浏览: 18
D. 它是iostream 类的虚基类。
ios 类是iostream 库中定义的一个基类,它是istream 类和ostream 类的基类。在C++中,iostream 库提供了一组用于进行输入和输出的标准工具,其中包括istream 类和ostream 类,它们分别用于从流中读取数据和向流中写入数据。由于这些类有很多共同的特性,如打开和关闭流、处理缓冲区等,因此将它们的共同特征抽象出来,定义了一个名为ios 的基类,并将其作为它们的虚基类。因此,选项A是错误的;选项B和C也是错误的,因为ios 类是istream 类和ostream 类的基类,而不是它们中的一个的基类。
相关问题
C++中ostream类的直接基类是ios。
解该问题,代码如下:
```
f = [100 150 200 250 300 200 150];
A = [-0.1 -0.2 -0.3 -0.4 -0.5 0 0; 0 0这是正确的。在C++中,ostream类是输出流的基类,它的直接基类是ios类。 0 0 0 0.1 0.2; 0 0 0 0 0.3 0ios类是输入输出流的基类,它定义了一些公共的功能和数据,例如流状态、流缓冲区等,同时它也是istream类的直接基类。因此,可以说ostream类是在ios类的基础.2 0.1];
b = [-1; 0; 0];
lb = zeros(7, 1);
ub =上扩展而来的。
write an overloaded friend ostream insertion operator function that allows a Fraction object to be output and appear in the form num/denom, using a cout statement. b. Write an overloaded friend istream extraction operator function that allows fractions in the form a/b to be input and assigned to a Fraction object.
Sure, I can help you with that!
Here is the implementation of the overloaded friend ostream insertion operator function for the Fraction class:
```c++
#include <iostream>
class Fraction {
private:
int numerator;
int denominator;
public:
Fraction(int num, int denom) : numerator(num), denominator(denom) { }
friend std::ostream& operator<<(std::ostream& os, const Fraction& frac);
};
std::ostream& operator<<(std::ostream& os, const Fraction& frac) {
os << frac.numerator << "/" << frac.denominator;
return os;
}
```
And here is the implementation of the overloaded friend istream extraction operator function for the Fraction class:
```c++
#include <iostream>
#include <sstream>
class Fraction {
private:
int numerator;
int denominator;
public:
Fraction(int num, int denom) : numerator(num), denominator(denom) { }
friend std::istream& operator>>(std::istream& is, Fraction& frac);
};
std::istream& operator>>(std::istream& is, Fraction& frac) {
std::string input;
is >> input;
std::stringstream ss(input);
int num, denom;
char slash;
ss >> num >> slash >> denom;
frac.numerator = num;
frac.denominator = denom;
return is;
}
```
You can use these overloaded operators to output and input Fraction objects as follows:
```c++
int main() {
Fraction f1(3, 4);
std::cout << f1 << std::endl; // outputs "3/4"
Fraction f2(0, 1);
std::cin >> f2; // inputs a Fraction from standard input in the form "num/denom"
std::cout << f2 << std::endl; // outputs the input Fraction
return 0;
}
```
I hope this helps! Let me know if you have any other questions.