C++ 无法在初始化中将浮点转换为浮点

我希望你们做得很好！我在这里寻求帮助，关于一个我不能很好地理解C++的错误。我是C++初学者，总体上是一个新的编码。这项作业将于晚上11:59完成，因此如果您能给出答案并加以解释，我们将不胜感激。谢谢大家

错误：

#include <iostream>
#include <cmath> 
#include <iomanip>
using namespace std;

//Prototypes:
//Gives user instructions 
void instructions(); 
//Asks user for number of books being bought and downloaded
int prompt();
//Calculation for Sub total without discount 
float calcSubTotal(float);
//Calculation for Discount 
float calcDiscount(int);
//Calculation for Total Cost
float total_cost(int);
//Outputs results for user 
void label(); 


        
int main()
{
instructions();
int nb = prompt(); //save value of prompt as pR
float subT = calcSubTotal(nb); //save value of calcSubTotal as subT
float Disc = calcDiscount(subT); //save value of calcDiscount as Disc
float totalC = total_cost(Disc); //save value of total_cost as totalc
label(); 
return 0;
}

//Instructions  Function 
void instructions(){
cout << "***************************************************************************" << endl; 
cout << " Hello and welcome to BandN Book Store!" << endl; 
cout << " Each eBook costs $8.99." << endl; 
cout << " Today, we are having a special where you can get 15% off your total order. " << endl;
cout << "***************************************************************************" << endl; 
}

//Number of books Function 
int prompt(){
    float books;
    cout << "How many ebooks do you wish to download?" << endl; 
    cin >> books;
return books; 
}

//calcSubTotal Function 
float calcSubTotal(float books){
    float Price_per_book = 8.99; 
    float subTotal = books * Price_per_book;    
return subTotal; 
}

//Discount Function 
float calcDiscount(int Price_Totaldisc){
    float subTotal = Price_Totaldisc;
    float disc = 0.15;  
    float discount = subTotal * disc; 
    float discount_value = subTotal - discount;
return discount_value; 
}

//Total Cost Fucntion
float total_cost(int dis_val){ 
float sub = calcSubTotal; //ERROR
float dis_value = dis_val; 
float totalcost = sub - dis_value; 

    return totalcost; 
}

//Prints Out results 
void label (int nb, float, float subT, float disc, float totalC){ 
    
cout << "***************************************" << endl; 
    cout << "The number of ebooks downloaded: " << nb << endl; 
    cout << setprecision(4); 
    cout << "Sub-total: " << "$" << subT << endl; 
    cout << setprecision(4); 
    cout << "Discount: " << "$" << disc << endl; 
    cout << setprecision(4);
    cout << "Total cost: " << '$' <<  totalC << endl; 
    cout << "***************************************" << endl; 
} 

在函数“int main（）”中： 28:7:警告：未使用的变量“totalC”[-Wunused变量]

在函数“浮动总成本（int）”中： 66:13:错误：无法在初始化中将“float（*）（float）”转换为“float”

代码：

#include <iostream>
#include <cmath> 
#include <iomanip>
using namespace std;

//Prototypes:
//Gives user instructions 
void instructions(); 
//Asks user for number of books being bought and downloaded
int prompt();
//Calculation for Sub total without discount 
float calcSubTotal(float);
//Calculation for Discount 
float calcDiscount(int);
//Calculation for Total Cost
float total_cost(int);
//Outputs results for user 
void label(); 


        
int main()
{
instructions();
int nb = prompt(); //save value of prompt as pR
float subT = calcSubTotal(nb); //save value of calcSubTotal as subT
float Disc = calcDiscount(subT); //save value of calcDiscount as Disc
float totalC = total_cost(Disc); //save value of total_cost as totalc
label(); 
return 0;
}

//Instructions  Function 
void instructions(){
cout << "***************************************************************************" << endl; 
cout << " Hello and welcome to BandN Book Store!" << endl; 
cout << " Each eBook costs $8.99." << endl; 
cout << " Today, we are having a special where you can get 15% off your total order. " << endl;
cout << "***************************************************************************" << endl; 
}

//Number of books Function 
int prompt(){
    float books;
    cout << "How many ebooks do you wish to download?" << endl; 
    cin >> books;
return books; 
}

//calcSubTotal Function 
float calcSubTotal(float books){
    float Price_per_book = 8.99; 
    float subTotal = books * Price_per_book;    
return subTotal; 
}

//Discount Function 
float calcDiscount(int Price_Totaldisc){
    float subTotal = Price_Totaldisc;
    float disc = 0.15;  
    float discount = subTotal * disc; 
    float discount_value = subTotal - discount;
return discount_value; 
}

//Total Cost Fucntion
float total_cost(int dis_val){ 
float sub = calcSubTotal; //ERROR
float dis_value = dis_val; 
float totalcost = sub - dis_value; 

    return totalcost; 
}

//Prints Out results 
void label (int nb, float, float subT, float disc, float totalC){ 
    
cout << "***************************************" << endl; 
    cout << "The number of ebooks downloaded: " << nb << endl; 
    cout << setprecision(4); 
    cout << "Sub-total: " << "$" << subT << endl; 
    cout << setprecision(4); 
    cout << "Discount: " << "$" << disc << endl; 
    cout << setprecision(4);
    cout << "Total cost: " << '$' <<  totalC << endl; 
    cout << "***************************************" << endl; 
} 

#包括
#包括
#包括
使用名称空间std；
//原型：
//提供用户说明
无效指令（）；
//询问用户购买和下载的图书数量
int提示符（）；
//无折扣小计的计算
浮标calcSubTotal（浮标）；
//折扣计算
浮点数（整数）；
//总成本的计算
浮动总成本（整数）；
//为用户输出结果
无效标签（）；
int main（）
{
指令（）；
int nb=prompt（）；//将提示的值另存为pR
float subT=calcSubTotal（nb）；//将calcSubTotal的值另存为subT
float Disc=calcDiscount（subT）；//将calcDiscount的值另存为Disc
float totalC=总成本（Disc）；//将总成本值另存为totalC
标签（）；
返回0；
}
//指令功能
无效指令（）{
cout您在
calcSubTotal
调用中缺少参数。您需要编写
float sub=calcSubTotal（在书中）
据我所知，当calcSubTotal是函数名时，您编写它就像一个变量。您需要说

float sub = calcSubTotal(books);

您需要调用prompt（），然后调用calcSubTotal（books），然后调用total_cost（dis_val）
我会在total_cost（）中定义一个浮动变量和小计

修复后，您需要修复主函数内部的label（）调用。我会让您这样做，但如果您需要任何帮助，我会：）
calcSubTotal
是一个函数。也许您想调用它？
calcSubTotal（somevar）
如果没有规范，就没有bug。也许他真的想分配这个函数，所以下面的行应该被修复？@MateuszDrost
float calcSubTotal（float）；
是一个规范。@MateuszDrost从上下文来看，OP似乎不太可能存储函数指针。指定的类型是
float
，稍后代码会尝试从中减去一个值。非常感谢！我感谢Zac的帮助！我会让你知道标签的。是的……我需要标签方面的帮助！哈哈。很抱歉。请告诉我您对标签Zac的代码知识！@Jonathan您的label（）函数需要参数才能工作。请确保您为它提供了所需的所有输入。