Count characters

Suppose you have a Rust str, and you want to count its characters like Microsoft Word. If we treat each space as a separate character, results are incorrect.

Method notes

In word processors, the logic counts sequential whitespace (like space chars) as single characters. This gives a more real-world estimate of character counts.

Example code

To begin, we introduce 2 Rust functions. The count_chars function is more interesting: it has logic to test for sequential whitespace.

fn count_chars(test: &str) -> i32 {
    let mut result = 0;
    let mut last_was_space = false;
    for c in test.chars() {
        // Only count whitespace chars that are not preceded by another whitespace.
        if c.is_whitespace() {
            if last_was_space == false {
                result += 1;
            }
            last_was_space = true;
        } else {
            result += 1;
            last_was_space = false;
        }
    }
    return result;
}

fn count_nonspace_chars(test: &str) -> i32 {
    let mut result = 0;
    for c in test.chars() {
        // Count all chars that are not whitespace.
        if !c.is_whitespace() {
            result += 1;
        }
    }
    return result;
}

fn main() {
    let test = "There is a cat, my friend.  How are you?";
    // Test the functions.
    let result1 = count_chars(test);
    let result2 = count_nonspace_chars(test);
    println!("RESULT1: {}", result1);
    println!("RESULT2: {}", result2);
}
RESULT1: 39
RESULT2: 31

Results note

In my previous research, I found that word processor signore sequential whitespace. And the Rust program results match results of existing methods.

A summary

It is possible to build functions in Rust that parallel existing software features. Having methods that can give results like this is useful.