C++ - Counting the number of vowels from a file - c++

Question

I'm having trouble implementing a feature that counts and displays the number of vowels from a file.
Here is the code I have so far.
#include <iostream>
#include <fstream>
#include <string>
#include <cassert>
#include <cstdio>
using namespace std;
int main(void)
{int i;
string inputFileName;
string s;
ifstream fileIn;
char ch;
cout<<"Enter name of file of characters :";
cin>>inputFileName;
fileIn.open(inputFileName.data());
assert(fileIn.is_open() );
i=0;
while (!(fileIn.eof()))
{
????????????
}
cout<<s;
cout<<"The number of vowels in the string is "<<s.?()<<endl;
return 0;
}
Note the question marks in the code.
Questions: How should I go about counting the vowels? Do I have to convert the text to lowercase and invoke system controls (if possible)?
Also, as for printing the number of vowels in the end, which string variable should I use, (see s.?)?
Thanks

Answer 1

auto isvowel = [](char c){ return c == 'A' || c == 'a' ||
c == 'E' || c == 'e' ||
c == 'I' || c == 'i' ||
c == 'O' || c == 'o' ||
c == 'U' || c == 'u'; };
std::ifstream f("file.txt");
auto numVowels = std::count_if(std::istreambuf_iterator<char>(f),
std::istreambuf_iterator<char>(),
isvowel);

Answer 2

You can using <algorithm>'s std::count_if to achieve this :
std::string vowels = "AEIOUaeiou";
size_t count = std::count_if
(
std::istreambuf_iterator<char>(in),
std::istreambuf_iterator<char>(),
[=]( char x)
{
return vowels.find(x) != std::string::npos ;
}
);
Or
size_t count = 0;
std::string vowels = "AEIOUaeiou";
char x ;
while ( in >> x )
{
count += vowels.find(x) != std::string::npos ;
}
Also read Why is iostream::eof inside a loop condition considered wrong?