How to multiply/divide one function to another ? How to use parameters? - c++

Question

How do I multiply a function to another function? and how do I properly use parameters?
I'm not exactly sure, I am really new to C++ with only about 14 weeks of class time.
Something I've tried would be creating a new function meant to multiply other functions and in the arguments I would put in the functions names.
For example:
float mealMath(numberOfAdults, mealChoosing){
//Rest of function
}
but I always get an error.Please explain how to fix this, this is a big obstacle in programming for me and I can't seem to grasp how to fix this or go about doing these things. Don't be to harsh on me for this.Thanks!
int numberOfAdults(){
int totalAdults;
cout << "Now how many adults will there be?: ";
cin >> totalAdults;
cout << "It seems there will be: " << totalAdults << " Adults." << endl;
while(totalAdults < 1){
cout << "Sorry there has to be a minimum of 1 adult!" << endl;
cout << "How many adults: ";
cin >> totalAdults;
}
return 0;
}
int numberOfKids(){
int totalKids;
cout << "Now how many Kids will there be?: ";
cin >> totalKids;
cout << "It seems there will be: " << totalKids << " kids." << endl;
while(totalKids < 0){
cout << "Sorry there has to be a minimum of 1 Kid!" << endl;
cout << "How many Kids: ";
cin >> totalKids;
}
return 0;
}
float mealChoosing(){
float cost;
string mealChoise;
cout << " " << endl;
cout << "Now, What meal will you be getting(D/S): ";
cin >> mealChoise;
if(mealChoise == "D"){
cout << "It seems you have selected the Deluxe Meal plan for everyone!" << endl;
cost = 25.95;
}
if(mealChoise == "S"){
cout << "It seems you have selected the Standard Meal plan for everyone!" << endl;
cost = 21.75;
}
cout << " " << endl;
return cost;
}
One expected result is I want to multiply the input that the user gives in function "numberOfAdults" to the input a user gives for "mealChoosing"
So I want numberOfAdults * mealChoosing but I want that done in a different function so
"float total(){
float totalBill;
totalBill = numberOfAdults * mealChoosing;
cout << totalBill;"
or something along those lines. I can't complete this project because I can't for some reason properly give the functions the proper information needed in parameters.

Answer 1

In this case(and most) you should not declare a function whose parameters are functions. Instead declare mealMath with an integer and a float input:
float mealMath(int a, float b){/*Your code here*/}
And then later call mealMath with the other two functions passed as arguments.
float x = mealMath(numberOfAdults(), mealChoosing());
Alternatively you can have no function parameters for mealMath() and instead call numberOfAdults() and mealChoosing() from inside of the function.
It's important to note that most of the time you'll be calling a function and using its output as an argument, and therefore you'll need to put the () after the function's identifier, instead of just typing the identifier alone.

Answer 2

Like mealChoosing() return totalAdults and totalKids (although its not needed here) from numberOfAdults(), numberOfKids() respectively.
int numberOfAdults() {
//...
return totalAdults;
}
int numberOfKids() {
//..
return totalKids;
}
float mealChoosing() {
//..
return cost;
}
Now on mealMath(numberOfAdults, mealChoosing)
float mealMathOutput = mealMath(numberOfAdults(), mealChoosing());