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/// Remove duplicate elements from a collection, preserving the order of their first occurrence.
///
/// This function takes a slice of items and returns a new `Vec<T>` containing only the unique elements,
/// preserving the order in which they first appear in the input collection.
///
/// **Note:** Unlike the previous implementation, this version does not require `T` to implement `Hash` and `Eq`.
/// This allows the function to work with types like floating-point numbers (`f32`, `f64`), which do not implement `Eq`
/// due to the presence of `NaN` (Not a Number) values.
///
/// However, this approach has a time complexity of O(n²) because it performs a linear search for each element to check for duplicates.
/// Use it with caution on large collections.
///
/// # Arguments
/// * `collection` - A slice of items from which to extract unique elements.
///
/// # Type Parameters
/// * `T` - The type of elements in the collection. Must implement `PartialEq` and `Clone`.
///
/// # Returns
/// * `Vec<T>` - A vector containing the unique elements from the input collection, in the order they first appear.
///
/// # Examples
/// ```rust
/// use lowdash::uniq;
/// let numbers = vec![1, 2, 2, 3, 4, 3, 5];
/// let unique_numbers = uniq(&numbers);
/// assert_eq!(unique_numbers, vec![1, 2, 3, 4, 5]);
/// ```
///
/// ```rust
/// use lowdash::uniq;
///
/// #[derive(Debug, PartialEq, Clone)]
/// 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: "Alice".to_string(), age: 25 },
/// Person { name: "Carol".to_string(), age: 35 },
/// ];
///
/// let unique_people = uniq(&people);
/// assert_eq!(unique_people, vec![
/// Person { name: "Alice".to_string(), age: 25 },
/// Person { name: "Bob".to_string(), age: 30 },
/// Person { name: "Carol".to_string(), age: 35 },
/// ]);
/// ```
pub fn uniq<T>(collection: &[T]) -> Vec<T>
where
T: PartialEq + Clone,
{
let mut seen = Vec::with_capacity(collection.len());
let mut result = Vec::with_capacity(collection.len());
for item in collection {
if !seen.contains(item) {
seen.push(item.clone());
result.push(item.clone());
}
}
result
}
#[cfg(test)]
mod tests {
use super::*;
#[derive(Debug, PartialEq, Clone)]
struct Person {
name: String,
age: u32,
}
#[test]
fn test_uniq_integers() {
let numbers = vec![1, 2, 2, 3, 4, 3, 5];
let unique_numbers = uniq(&numbers);
assert_eq!(unique_numbers, vec![1, 2, 3, 4, 5]);
}
#[test]
fn test_uniq_strings() {
let strings = vec!["apple", "banana", "apple", "cherry", "banana"];
let unique_strings = uniq(&strings);
assert_eq!(unique_strings, vec!["apple", "banana", "cherry"]);
}
#[test]
fn test_uniq_with_structs() {
let people = vec![
Person {
name: "Alice".to_string(),
age: 25,
},
Person {
name: "Bob".to_string(),
age: 30,
},
Person {
name: "Alice".to_string(),
age: 25,
},
Person {
name: "Carol".to_string(),
age: 35,
},
];
let unique_people = uniq(&people);
assert_eq!(
unique_people,
vec![
Person {
name: "Alice".to_string(),
age: 25
},
Person {
name: "Bob".to_string(),
age: 30
},
Person {
name: "Carol".to_string(),
age: 35
},
]
);
}
#[test]
fn test_uniq_with_empty_collection() {
let empty: Vec<i32> = vec![];
let unique = uniq(&empty);
assert_eq!(unique, Vec::<i32>::new());
}
#[test]
fn test_uniq_with_no_duplicates() {
let collection = vec![1, 2, 3, 4, 5];
let unique = uniq(&collection);
assert_eq!(unique, vec![1, 2, 3, 4, 5]);
}
#[test]
fn test_uniq_with_all_duplicates() {
let collection = vec![1, 1, 1, 1, 1];
let unique = uniq(&collection);
assert_eq!(unique, vec![1]);
}
#[test]
fn test_uniq_with_floats() {
let float_collection = vec![1.1, 2.2, 2.2, 3.3, 4.4, 3.3, 5.5];
let unique_floats = uniq(&float_collection);
assert_eq!(unique_floats, vec![1.1, 2.2, 3.3, 4.4, 5.5]);
}
#[test]
fn test_uniq_with_characters() {
let chars = vec!['a', 'b', 'a', 'c', 'b', 'd'];
let unique_chars = uniq(&chars);
assert_eq!(unique_chars, vec!['a', 'b', 'c', 'd']);
}
#[test]
fn test_uniq_preserves_order() {
let numbers = vec![3, 1, 2, 3, 2, 4, 1, 5];
let unique_numbers = uniq(&numbers);
assert_eq!(unique_numbers, vec![3, 1, 2, 4, 5]);
}
#[test]
fn test_uniq_with_mixed_types() {
#[derive(Debug, PartialEq, Clone)]
struct Item {
id: u32,
value: String,
}
let items = vec![
Item {
id: 1,
value: "one".to_string(),
},
Item {
id: 2,
value: "two".to_string(),
},
Item {
id: 1,
value: "one".to_string(),
},
Item {
id: 3,
value: "three".to_string(),
},
];
let unique_items = uniq(&items);
assert_eq!(
unique_items,
vec![
Item {
id: 1,
value: "one".to_string()
},
Item {
id: 2,
value: "two".to_string()
},
Item {
id: 3,
value: "three".to_string()
},
]
);
}
#[test]
fn test_uniq_with_optionals() {
let collection = vec![Some(1), None, Some(2), Some(1), None, Some(3), Some(2)];
let unique = uniq(&collection);
assert_eq!(unique, vec![Some(1), None, Some(2), Some(3),]);
}
#[test]
fn test_uniq_with_nan_floats() {
let float_collection = vec![std::f64::NAN, std::f64::INFINITY, std::f64::NAN, 1.0];
let unique_floats = uniq(&float_collection);
// Note: NaN != NaN, so each NaN is considered unique
assert_eq!(unique_floats.len(), 4);
assert!(unique_floats[0].is_nan());
assert!(unique_floats[1].is_infinite());
assert!(unique_floats[2].is_nan());
assert_eq!(unique_floats[3], 1.0);
}
}