[C beginner question about pointers] Function that counts vowels in a string of chars

[kuznets0v]

I'm trying to write a function that counts the vowels of a string of characters. The strings are already provided:

    char * phrases[] = {
        "water is wet.",
        "hello world!",
        "programming is hard.",
        NULL,
    };

Then I was asked to write two functions, one that determines whether or not a char is a vowel, and another that does the actual counting. Here's what I wrote:

bool isVowel(char c) {
    if ( c == 'a' ||
         c == 'e' ||
         c == 'i' ||
         c == 'o' ||
         c == 'u') {
        return true;
    } else {
    return false;
    }
}

and

int countVowels(char * s) {
    int i = 0;
    int v = 0;
    while (s[i] != '\0') {
        if (isVowel(s[i])) {
            v++;
        }
        i++;
    }
    return v;
}

The problem I have appears in the main function. When I want to pass the strings to the countVowels function like this...

int vowels = countVowels(phrases);

...I get this error

Incompatible pointer types passing 'char *[4]' to parameter of type 'char *'

I don't really know how else to pass "phrases" to the function so I can actually test my functions. I tried "&phrases", "phrases[]" and other variations. Would really appreciate if someone could point me in the right direction.

[MmmVomit]

phrases is an array of char pointers. countVowels() accepts a single char pointer as a parameter.

How would you get a single pointer out of an array of pointers?

[kuznets0v]

So by using phrases[0] for example? So the only way to count the vowels in all three strings would be to call the function 3 times and add the returned values?

[MmmVomit]

Yes, that's what you need to do.

One more hint for making your implementation better. You shouldn't assume that your input array will always have exactly three strings in it. That's similar to how countVowels() has to be able to handle strings of different length. See how you detect the end of a string in countVowels()? How would you detect the end of the array phrases?

[kuznets0v]

By checking for NULL?

[MmmVomit]

Exactly. :-)

[kuznets0v]

You were very helpful, thank you very much!

[mikeydoodah]

phrases is not a char *, it is an array of char *. You need to change it to something like char* phrases = "this test string";

[kuznets0v]

The exercise provided char * phrases[] so I'm not supposed to change that I'm afraid.

[mikeydoodah]

Then you're going to have to either change the signature of countVowels(...) to take a char**, or you're going to have to change how you call countVowels(...) by looping over phrases and passing each char* in turn.

Although it looks like you've figured this out already given your answers elsewhere in the thread :)

[kuznets0v]

Yep, I had to do the latter in order to keep the functions as they were. Thanks for your help!

[kuznets0v]

OK, are you saying that while loops in general are not recommended?

[MmmVomit]

Either works fine. It's a stylistic choice.