对函数的未定义引用 (C++）

检查你的start函数，如M.M.所述，你应该得到这样的东西：

float start() {
    // ...
    float balance;
    cin >> balance;
    return balance;
}

int main() {
    float n;
    n = start();
    // ...
    return 0;
}

并逐步检查所有函数，因为您在下一个函数中遇到问题process：in if 语句必须是比较运算符if (type == "C" || type == "c")而不是赋值type = "C"||"c"。

你声明一个函数void start(); .你用start();来称呼它.

但是，您从未提供此功能的正文。 定义为void start(float balance)的函数是不同的函数。在C++中，可能有几个名称相同但参数列表不同的函数;这些是不同的功能。

您在process()等方面也有类似的问题。

您的函数应该传递和返回它们使用的变量，但您实际上并没有编写函数来执行此操作。 void start(float balance) 中的balance与 main() 内部的float balance不同;您在此功能中所做的更改不会影响float balance; main 。

要修复此特定功能，它应该是：

float start();

在原型和函数定义中;你应该在函数内部有float balance;，然后以return balance;结尾。然后你像这样打电话给main：balance = start();

您的课程材料应涵盖将值传递给函数和从函数返回值，您需要查阅它们以修复其他函数。

请使用此代码。这将对您有所帮助。

#include <iostream>
#include <iomanip>
using namespace std;
void start(float balance);
void process(float balance, float amount, char type, bool endcheck);
void check(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal);
void deposit(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal);
const float dserv = 0.10;
const float cserv = 0.15;
const float fiveserv = 5.0;
const float oserv = 10.0;
int main()
{
float balance;
float amount;
bool fivehun;
bool endcheck;
float servcharge;
float servchargetotal;
char type;
start(balance);
while(endcheck != true)
{process(balance, amount, fivehun, servcharge, servchargetotal);}
cout<<"Current balance: $"<<balance<<endl;
cout<<"Total service charges: $"<<servchargetotal<<endl;
cout<<"Final balance: $"<<
system("pause");
return 0;
}
void start(float balance)
{
balance = 0;
cout<<fixed<<showpoint<<setprecision(2);
cout<<"Transactions will take the form of a letter followed by a dollar ";
cout<<"amount. Valid letters are “C” for a check, “D” for a deposit, and";
cout<<"“E” for the ending transaction (use zero on this transaction).";
cout<<"Press <Enter> after each line of input";
cout<<"Enter the beginning balance:"<<endl;
cin>>balance;
}
void process(float balance, float amount, char type, bool endcheck)
{
cout<<"Enter a transaction:"<<endl;
cin>>type>>amount;
if (type = "C"||"c")
{check(balance, amount, ...);
endcheck = false;}
else if(type = "D"||"d")
{deposit(balance, amount, ...);
endcheck = false;}
else if(type= "E"||"e")
{endcheck = true;}
}
void check(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal)
{
balance = balance - amount;
servcharge = cserv;
if (balance<500.00)
{fivehun = true;}
else
{fivehun = false;}
cout<<"Transaction: Check in amount of $"<<amount<<endl;
cout<<"Current balance: $"<<balance<<endl;
cout<<"Service charge: Check - $"<<cserv<<endl;
if (fivehun == true)
{cout<<"Service charge: Below $500 - $"<<fiveserv<<endl;
 servcharge = (fiveserv+servcharge);}
cout<<"Total service charges: $"<<servcharge<<endl;
servchargetotal = servchargetotal + servcharge;
}
void deposit(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal)
{
balance = balance + amount;
servcharge = dserv;
if (balance<500.00)
{fivehun = true;}
else
{fivehun = false;}
cout<<"Transaction: Deposit in amount of $"<<amount<<endl;
cout<<"Current balance: $"<<balance<<endl;
cout<<"Service charge: Check - $"<<cserv<<endl;
if (fivehun == true)
{cout<<"Service charge: Below $500 - $"<<fiveserv<<endl;
 servcharge = (fiveserv+cserv);}
cout<<"Total service charges: $"<<servcharge<<endl;
servchargetotal = servchargetotal + servcharge;
}

定义以下函数：

void start();
void process();
void check();
void deposit();

您实现：

void start(float balance)
void process(float balance, float amount, char type, bool endcheck)
void check(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal)
void deposit(float balance, float amount, bool fivehun, float servcharge, float& servchargetotal)

定义必须与实现匹配。

或者，如果您将实现放在文件中首次使用(main(之前，则可以删除定义。

调用与定义匹配，但是当编译器(实际上是链接器(寻找看起来像void start()的函数实现时，它找到了void start(float balance)并得出结论，这些不是足够接近的匹配。