Find vowels in string not working

Question

My program checks if an input string contains vowels. In case no vowels were found, it prints "not found".

string stringInput;
cout << "Enter a sentence: ";
cin >> stringInput;
if ((stringInput.find('a')) || (stringInput.find('e')) || (stringInput.find('i')) || 
    (stringInput.find('o')) || (stringInput.find('u')) != string::npos)
{
    cout << "not found";
}
else
{
    cout << "found";
}

Regardless of the input, everytime I run the program, it prints "not found".

Hint: Look at the return value of `std::string::find`. I suggest you to look into `std::string::find_first_of`. — Algirdas Preidžius, Feb 17 '17 at 21:26
`find` returns the position of the character, not `true` or `false`. It returns `npos` if the value is not found. — François Andrieux, Feb 17 '17 at 21:26
In addition to what Algirdas suggested, also checkout `string::npos`. Also see [What does string::npos mean](http://stackoverflow.com/q/3827926/608639). — jww, Feb 17 '17 at 21:41

Fureeish · Answer 1 · 2017-02-17T21:45:43.163

1

That's because string::find does not return bool. It returns an iterator the the found element. If the element was not found, it returns string::npos. The appropriate way of doing this is checking whether the function returned something else than string::npos.

Take a look at this example:

std::string Name = "something";
if(Name.find('g') != std::string::npos) std::cout << "Found the letter 'g'!";
else std::cout << "There is no letter 'g' in the string Name.";

If you understand the example above, I'm sure you will be able to edit your code and get the expected result.

EDIT: as Tobi303 mentioned, the problem lies with only one instance of != string::npos. Creating logical statements are something || something || something you expect something to be a bool. In this case, you should compare EACH instance of string::find with string::npos. That would look like this:

if((stringInput.find('a')) != std::string::npos || (stringInput.find('e')) != std::string::npos || (stringInput.find('i')) != std::string::npos || (stringInput.find('o')) != std::string::npos || (stringInput.find('u')) != string::npos){//code}

edited Feb 17 '17 at 21:45

answered Feb 17 '17 at 21:29

Fureeish

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he has the `!= sting::npos`, but only once. – 463035818_is_not_an_ai Feb 17 '17 at 21:40
1

seems like OP knowns about what `find` returns, but not how to or several conditions – 463035818_is_not_an_ai Feb 17 '17 at 21:41
@tobi303, I edited the answer mentioning your input. I originally thought that OP was expecting `bool` return value from `string::find`. Good catch – Fureeish Feb 17 '17 at 21:47
you could add that the iterator returned by find is converted to bool and only the first condition was ever evaluated in his code – 463035818_is_not_an_ai Feb 17 '17 at 21:48
.. and please add some formatting. The ugly long line caused already enough confusion in OPs code ;) – 463035818_is_not_an_ai Feb 17 '17 at 21:49

Find vowels in string not working

1 Answers1