A C++ program to convert a sentence to Pig Latin

iglatinpay.cpp

#include <algorithm>
#include <iostream>
#include <string>

using namespace std;

// is_vowel returns true if the given
// character is a vowel; false otherwise.
bool is_vowel(char c)
{
    c = tolower(c);
    return c == 'a'
        or c == 'e'
        or c == 'i'
        or c == 'o'
        or c == 'u'
        or c == 'y'
        ;
}

// to_piglatin translates a string to piglatin.
//
// For words that begin with consonant sounds,
// the initial consonant or consonant cluster
// is moved to the end of the word, and "ay"
// is added.
// For words that begin with vowel sounds or
// silent letter, you just add "way".
string to_piglatin(string& s)
{
    auto it = find_if(begin(s), end(s), is_vowel);
    if (it == begin(s)) {
        s += "way";
    }
    else if (it != end(s)) {
        rotate(begin(s), it, end(s));
        s += "ay";
    }
    return s;
}

int main(int argc, char* argv[])
{
    string s;
    for (int i = 1; i < argc; i++) {
        s = argv[i];
        cout << to_piglatin(s) << " ";
    }
    cout << endl;
    return 0;
}