lo_ 0.3.1

A modern Rust utility library delivering modularity, performance & extras ported from JavaScript Lodash
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74

/// Converts the first character of string to lower case.
///
/// # Example
/// ```rust
/// use lo_::lower_first;
/// assert_eq!(lower_first("Fred"), "fred");
/// assert_eq!(lower_first("FRED"), "fRED");
///
/// ```
///
pub fn lower_first(string: &str) -> String {
    let mut result = String::with_capacity(string.len());
    let mut is_first_char = true;

    for c in string.chars() {
        if is_first_char && c.is_alphanumeric() {
            result.push(c.to_ascii_lowercase());
            is_first_char = false;
        } else {
            result.push(c);
        }
    }

    result
}

#[cfg(test)]
mod tests {
    use super::lower_first;

    #[test]
    fn test_lower_first_empty_string() {
        let input = "";
        let result = lower_first(input);
        assert_eq!(result, "");
    }

    #[test]
    fn test_lower_first_single_char() {
        let input = "A";
        let result = lower_first(input);
        assert_eq!(result, "a");
    }

    #[test]
    fn test_lower_first_all_lowercase() {
        let input = "rust";
        let result = lower_first(input);
        assert_eq!(result, "rust");
    }

    #[test]
    fn test_lower_first_all_uppercase() {
        let input = "RUST";
        let result = lower_first(input);
        assert_eq!(result, "rUST");
    }

    #[test]
    fn test_lower_first_mixed_case() {
        let input = "RusT";
        let result = lower_first(input);
        assert_eq!(result, "rusT");
    }

    #[test]
    fn test_lower_first_with_space() {
        // Test with a string containing spaces
        assert_eq!(
            lower_first("  This is a test"),
            "  this is a test".to_string()
        );
    }
}