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/// Find the first item in a collection that satisfies a predicate.
/// If no item satisfies the predicate, return the fallback value.
///
/// # Arguments
/// * `collection` - A collection of items.
/// * `fallback` - Value to return if no item satisfies the predicate.
/// * `predicate` - A function that takes an item from the collection and returns a boolean.
///
/// # Returns
/// * `&T` - Either the first item that satisfies the predicate or the fallback value.
///
/// # Examples
/// ```rust
/// use lowdash::find_or_else;
/// let numbers = vec![1, 2, 3, 4, 5];
/// let predicate = |x: &i32| *x == 3;
/// let result = find_or_else(&numbers, &0, predicate);
/// assert_eq!(result, &3);
/// ```
///
/// ```rust
/// use lowdash::find_or_else;
/// let numbers = vec![10, 20, 30, 40];
/// let result = find_or_else(&numbers, &0, |x| *x > 50);
/// assert_eq!(result, &0);
/// ```
///
/// ```rust
/// use lowdash::find_or_else;
///
/// #[derive(Debug, PartialEq)]
/// struct Person {
/// name: String,
/// age: u32,
/// }
///
/// let people = vec![
/// Person { name: "Alice".to_string(), age: 25 },
/// Person { name: "Bob".to_string(), age: 30 },
/// Person { name: "Carol".to_string(), age: 35 },
/// ];
///
/// let fallback = Person { name: "Unknown".to_string(), age: 0 };
/// let result = find_or_else(&people, &fallback, |p| p.age > 30);
/// assert_eq!(result, &Person { name: "Carol".to_string(), age: 35 });
/// ```
pub fn find_or_else<'a, T, F>(collection: &'a [T], fallback: &'a T, predicate: F) -> &'a T
where
F: Fn(&T) -> bool,
{
for item in collection {
if predicate(item) {
return item;
}
}
fallback
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_find_or_else() {
let collection = vec![1, 2, 3, 4, 5];
let predicate = |x: &i32| *x == 3;
let result = find_or_else(&collection, &0, predicate);
assert_eq!(result, &3);
}
#[test]
fn test_find_or_else_with_inline_predicate() {
let numbers = vec![10, 20, 30, 40];
let result = find_or_else(&numbers, &0, |x| *x > 25);
assert_eq!(result, &30);
}
#[test]
fn test_find_or_else_not_found() {
let collection = vec![1, 2, 3, 4, 5];
let predicate = |x: &i32| *x == 6;
let result = find_or_else(&collection, &0, predicate);
assert_eq!(result, &0);
}
#[test]
fn test_find_or_else_empty_collection() {
let collection: Vec<i32> = vec![];
let predicate = |x: &i32| *x == 3;
let result = find_or_else(&collection, &0, predicate);
assert_eq!(result, &0);
}
#[test]
fn test_find_or_else_with_struct() {
#[derive(Debug, PartialEq)]
struct Person {
name: String,
age: u32,
}
let people = vec![
Person {
name: "Alice".to_string(),
age: 25,
},
Person {
name: "Bob".to_string(),
age: 30,
},
Person {
name: "Carol".to_string(),
age: 35,
},
];
let fallback = Person {
name: "Unknown".to_string(),
age: 0,
};
let result = find_or_else(&people, &fallback, |p| p.age > 30);
assert_eq!(
result,
&Person {
name: "Carol".to_string(),
age: 35
}
);
let name_result = find_or_else(&people, &fallback, |p| p.name.starts_with("B"));
assert_eq!(
name_result,
&Person {
name: "Bob".to_string(),
age: 30
}
);
let not_found = find_or_else(&people, &fallback, |p| p.age > 40);
assert_eq!(
not_found,
&Person {
name: "Unknown".to_string(),
age: 0
}
);
}
#[test]
fn test_find_or_else_with_floats() {
let floats = vec![1.1, 2.2, 3.3, 4.4, 5.5];
let fallback = 0.0;
let result = find_or_else(&floats, &fallback, |x| *x > 3.0);
assert_eq!(result, &3.3);
let not_found = find_or_else(&floats, &fallback, |x| *x > 6.0);
assert_eq!(not_found, &0.0);
}
}