Error in a function call [closed] - c++

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Write a function NumberOfPennies() that returns the total number of pennies given a number of dollars and (optionally) a number of pennies. Ex: 5 dollars and 6 pennies returns 506.
For the above question, here is the code below.
Getting an error: error: no matching function for call to 'NumberOfPennies(int)'
#include <iostream>
using namespace std;
int NumberOfPennies(int one,int two)
{
return (one*100+two);
}
int main() {
cout << NumberOfPennies(5, 6) << endl; // Should print 506
cout << NumberOfPennies(4) << endl; // Should print 400
return 0;
}
However, when I put int two=0 in the function NumberOfPennies it is working. Why is this so? Can anyone please explain this.
#include <iostream>
using namespace std;
int NumberOfPennies(int one,int two=0)
{
return (one*100+two);
}
int main() {
cout << NumberOfPennies(5, 6) << endl; // Should print 506
cout << NumberOfPennies(4) << endl; // Should print 400
return 0;
}

Answer 1

The fact that you have written int two = 0 in the second snippet is your supporting a default value of that parameter two of 0.
This means that it can be omitted at the calling site with the default value assumed if it is, so
cout << NumberOfPennies(4) << endl;
and
cout << NumberOfPennies(4, 0) << endl;
are equivalent. If you don't code your function to support a default value then you need to use two arguments to call NumberOfPennies.
(In order to improve readability consider renaming your parameters one and two to dollars and cents respectively).

Answer 2

There is a concept called default parameter in C++. Look up this link https://www.programiz.com/cpp-programming/default-argument.
In the first case, it is not able to resolve the function call to any existing function call taking just one integer parameter and fails.
int NumberOfPennies(int one,int two).
In the second case, int NumberOfPennies(int one,int two=0) as we have mentioned that if the second integer is not passed assume a default value of 0.During the first run compiler is not able to find a function that takes just one integer parameter. Next, it looks for possible cases where you have a function with 2 integer inputs with one of them having a default value. Your function matches this case and hence compilation is successful.
(Additional info: Its good to write function names and arguments that are intutive. Suggest you to rename arguments as int NumberOfPennies(int dollars,int cents))

Answer 3

"I ran the code below but it is not working"
is not a useful description of your problem.
Why is this so? Can anyone please explain this.
Your problem is clearly described in the compiler error report, which you should include in your post.
error: no matching function for call to ‘NumberOfPennies(int)’
std::cout << NumberOfPennies(4) << std::endl;
^
note: candidate: int NumberOfPennies(int, int)
int NumberOfPennies(int one, int two)
^~~~~~~~~~~~~~~
note: candidate expects 2 arguments, 1 provided
Thus, you tried to invoke the function with 1 argument, when your declaration requires 2.
By adding the default value for the second parameter,
int NumberOfPennies(int one,int two=0) ...
You have provided a value for the second parameter when not provided.
Review default function parameter.