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/// Converts the first character of string to lower case.
///
/// # Arguments
///
/// * `s` - The string to convert.
///
/// # Returns
///
/// Returns the converted string.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use rufl::string;
///
/// assert_eq!("fOO", string::lower_first("FOO"));
///
/// assert_eq!("_fOO", string::lower_first("_fOO"));
///
/// assert_eq!("foo_Bar", string::lower_first("Foo_Bar"));
///
/// assert_eq!("foo Bar", string::lower_first("Foo Bar"));
///
/// ```
pub fn lower_first(s: impl AsRef<str>) -> String {
match s.as_ref().len() {
0 => s.as_ref().to_string(),
_ => s
.as_ref()
.chars()
.enumerate()
.map(|(i, item)| match i {
0 => item.to_lowercase().to_string(),
_ => item.to_string(),
})
.collect::<Vec<String>>()
.join(""),
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::collections::HashMap;
#[test]
fn test_lower_first() {
let case_list: Vec<(String, String)> = vec![
("foo".to_string(), "foo".to_string()),
("FOo".to_string(), "fOo".to_string()),
("foo_".to_string(), "foo_".to_string()),
("Foo Bar".to_string(), "foo Bar".to_string()),
("_foo".to_string(), "_foo".to_string()),
("Foo_Bar".to_string(), "foo_Bar".to_string()),
("Foo-bar".to_string(), "foo-bar".to_string()),
];
let case_map: HashMap<String, String> = case_list.into_iter().collect();
for (key, value) in case_map {
assert_eq!(value, lower_first(key));
}
}
}