C++ 前缀计算器在编译时遇到问题

我在一个程序中遇到了一些问题，该程序应该采用命令行表达式并将其解释为正常的数学表达式。这就是我得到的错误：

driver.cpp:在函数“int mainit，char**”中： driver.cpp:17:57:错误：调用'PrefixCalculator:：evalstd:：istringstream'没有匹配的函数

司机：cpp:17:57：注：候选人为： PrefixCalculator.h:33:3:note:T PrefixCalculator:：evalstd:：istringstream&[with T=int，std:：istringstream=std:：basic_istringstream]

PrefixCalculator.h:33:3:注意：参数1从'std:：istringstream{aka std:：basic_istringstream}'到'std:：istringstream&{aka std:：basic_istringstream&}'没有已知的转换

我不明白这个错误试图向我暗示什么。 有没有解决这个问题的建议？稍后我将添加异常，因此它们现在将被注释掉

代码如下：

PrefixCalculator.cpp

#pragma once
#include <sstream>

using namespace std;

template<class T>
class PrefixCalculator {
public:
PrefixCalculator(void){
    numOperator = 0;
    numOperand = 0;
};
~PrefixCalculator(void){};

T eval(istringstream&);

int getNumOperator() {
    return numOperator;
};

int getNumOperand() {
    return numOperand;
};

private:
//if you feel you need private helper functions and/or helper data
int numOperator;
int numOperand;
};

template<class T>
T PrefixCalculator<T>::eval(istringstream& input) { 
 //this function needs to throw an exception if there's a problem with the expression or operators
char nextChar = input.peek();

//this while loop skips over the spaces in the expression, if there are any
while(nextChar == ' ') {
    input.get();    //move past this space
    nextChar = input.peek(); //check the next character
}

if(nextChar == '+') {
    input.get();    //moves past the +
    numOperator++;
    return eval(input) + eval(input);   //recursively calculates the first expression, and adds it to the second expression, returning the result
}

/***** more operators here ******/
if(nextChar == '-') {
    input.get();
    numOperator++;
    return eval(input) - eval(input);
}

if(nextChar == '*') {
    input.get();
    numOperator++;
    return eval(input) * eval(input);
}

if(nextChar == '/') {
    input.get();
    numOperator++;
    return eval(input) / eval(input);
} 

/******  BASE CASE HERE *******/
//it's not an operator, and it's not a space, so you must be reading an actual value (like '3' in "+ 3 6".  Use the >> operator of istringstream to pull in a T value!
input>>nextChar;
T digit = nextChar - '0';
numOperand++;
return digit;
//OR...there's bad input, in which case the reading would fail and you should throw an exception

}

driver.cpp

#include <sstream>
#include <string>
#include <iostream>
#include "PrefixCalculator.h"

using namespace std;

int main(int argc, char** argv) {
PrefixCalculator<int> calc;

string expression;
cout << "Give a prefix expression to evaluate, or q to quit." << endl;
getline(cin,expression);

while(expression[0] != 'q') {
    //try {
        int result = calc.eval(istringstream(expression));
        cout << result << endl;
    //}
    //catch { //will not compile, you have to finish this!
    //  
    //}

    cout << "Give a prefix expression to evaluate or q to quit." << endl;
    getline(cin,expression);
}

return 0;
 }

计算evalistringstreamexpression；将一个临时实例传递给eval，则需要一个左值。 为流提供一个额外的变量

 istringstream iss(expression); 

把那个递给我

 int result = calc.eval(iss);