Very simple function I can't execute - c++

Question

I am a student and I'm trying to write a function that returns "true" if I enter a vowel, and "false" if I enter a consonant.
This is what I wrote:
#include <iostream>
using namespace std;
int main()
{
bool isVowel(char x);
}
bool isVowel(char x)
{
cout << "Enter a letter" << endl;
cin >> x;
if (x == 'a', 'e', 'i', 'o', 'u')
return true;
else
return false;
}
I compiled with g++ isvowel.cpp -o isvowel, and apparently there were no errors, but then I tried to execute using ./isvowel and nothin happened.
What's wrong?

Answer 1

Your if equality comparison does not work. As Sam stated in the comments, you need to exlicitely compare x with each value.
bool isVowel(char x)
{
// The if is not really needed here since you can
// just return the result of the comparison
if (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u') {
return true;
}
else {
return false;
}
}
To call this method:
std::cout << "Input character" << std::endl;
char x;
std::cin >> x;
bool vowel = isVowel(x);
std::cout << "Is vowel: " << vowel << std::endl;

Answer 2

The comma doesn't work that way you think (it's been explained above), but the reason that nothing happens is because you don't really call the isVowel function. The code
bool isVowel(char x);
defines a new function that hides the one you meant to call. To make this work, you need to call the function correctly, i.e.
isVowel('x'); // or, better, isVowel(), as I'll explain below
and move the isVowel function definition above main, because otherwise it wouldn't be visible inside main. The third thing is, the "char x" parameter you pass to the function doesn't really do anything, since you overwrite it with cin >> x; You probably want to use a method that takes no parameters. And finally, if you want to see the result, you need to print it to the screen. So, to put this together, your code should look like:
#include <iostream>
using namespace std;
bool isVowel()
{
cout << "Enter a letter" << endl;
char x;
cin >> x;
if (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u')
return true;
else
return false;
}
int main()
{
bool b = isVowel();
cout << b << endl;
}
or, if you prefer,
#include <iostream>
using namespace std;
bool isVowel(char x)
{
if (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u')
return true;
else
return false;
}
int main()
{
cout << "Enter a letter" << endl;
char x;
cin >> x;
bool b = isVowel(x);
cout << b << endl;
}