Count Vowels
This function should take a string as an input and return the count of vowels (a, e, i, o, u) in the string. The function should be case-insensitive.
Input: String (str).
Output: Integer (int).
Examples:
assert count_vowels("hello") == 2
assert count_vowels("openai") == 4
assert count_vowels("typescript") == 2
assert count_vowels("a") == 1
How it’s used:
- in natural language processing tasks, like text analysis and statistics;
- in text-based games or learning applications, for instance, to calculate the difficulty level of a word or phrase.
Preconditions:
- text ∈ string;
- length(text) >= 0.
