我正在重载流提取操作符,以便它可以在我创建的Complex类中使用.当我使用cin从from(x,y)中的用户输入一个复数时,它工作正常.请注意,我忽略了这些字符“(,)”.因为我只想要数字.
但是当我尝试以相同的格式从用户输入两个数字时,无论输入什么值,程序都会返回(0,0)作为答案.看起来程序无法忽略这些字符,在这种情况下.我无法找到解决此问题的方法.这是文件.
请仔细查看main.cpp和输出.我输入了这样的价值,
(2,3)
(5,6)
如何编辑此代码,以便即使输入一个复数或输入更多数字它也能正常工作?
Complex.h
#pragma once
#include <iostream>
using namespace std;
#ifndef COMPLEX_H
#define COMPLEX_H
class Complex {
public:
// constructors
Complex(double, double);
Complex(double);
Complex();
friend ostream & operator<<(ostream &,Complex &);
friend istream & operator>>(istream &, Complex &);
private:
double r;
double i;
};
#endif
Complex.cpp
#include <iostream>
using namespace std;
#include "Complex.h"
Complex::Complex(double _r, double _i){
r=_r;
i=_i;
}
Complex::Complex(double _r){
r=_r;
i=0.0;
}
Complex::Complex(){
r=0.0;
i=0.0;
}
// Code for overloading stream insertion operator.
ostream& operator<<(ostream& os, Complex& value){
os << "(" << value.r <<", " << value.i << ")" ;
return os;
}
// Code for overloading stream extraction operator.
istream & operator>>(istream& is, Complex& val){
is.ignore();
is >>val.r;
is.ignore();
is >>val.i;
return is;
}
main.cpp中
#include <iostream>
#include "Complex.h"
using namespace std;
int main(){
Complex x,y;
cout<<"Enter complex number in the form(x,y): "<<endl;
cin>>x>>y;
cout<<"\nThe 1st complex number entered was "<<x<<endl;
cout<<"\nThe 2nd complex number entered was "<<y<<endl;
}
产量
The 1st complex number entered was (2,3)
The second complex number entered was (0,0)
解决方法: @Holt是对的,第二次调用运算符>>()中的第一个ignore()调用正在丢弃前一个输入中的剩余换行符.如果角色事先已被清除(可能通过在从函数返回之前清空空格或进入时),它就会起作用.
更直观的方法是编写自己的skip<>函数模板,首先清除空格,然后丢弃您提供的字符(如果存在).典型的实现如下所示:
template<char n>
std::istream& skip(std::istream& is)
{
if ((is >> std::ws).peek() != n)
is.setstate(std::ios_base::failbit);
else
return is.ignore();
return is;
}
您可以在提取器中使用它,如下所示:
std::istream& operator>>(std::istream& is, Complex& val) {
is >> skip<'('> >> val.r >> skip<','> >> val.i >> skip<')'>;
return is;
}
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