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/// Returns a subset of the collection based on the provided start and end indices.
///
/// This function extracts a subset from the given collection starting at the specified `start` index
/// and ending before the `end` index. If the `start` or `end` indices are negative, they are offset
/// from the end of the collection. The function ensures that the resulting subset does not exceed
/// the bounds of the original collection.
///
/// **Time Complexity:** O(n), where n is the number of elements in the subset.
///
/// # Arguments
///
/// * `collection` - A slice of items from which to extract the subset.
/// * `start` - The starting index for the subset. Can be negative to indicate an offset from the end.
/// * `end` - The ending index for the subset. Can be negative to indicate an offset from the end.
///
/// # Type Parameters
///
/// * `T` - The type of elements in the collection. Must implement `Clone`.
///
/// # Returns
///
/// * `Vec<T>` - A vector containing the subset of elements.
///
/// # Examples
///
/// ```rust
/// use lowdash::slice;
///
/// let numbers = vec![1, 2, 3, 4, 5];
/// let result = slice(&numbers, 1, 3);
/// assert_eq!(result, vec![2, 3]);
/// ```
///
/// ```rust
/// use lowdash::slice;
///
/// let numbers = vec![1, 2, 3, 4, 5];
/// let result = slice(&numbers, -3, -1);
/// assert_eq!(result, vec![3, 4]);
/// ```
///
/// ```rust
/// use lowdash::slice;
///
/// #[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: "Carol".to_string(), age: 35 },
/// Person { name: "Dave".to_string(), age: 40 },
/// ];
///
/// let result = slice(&people, 1, 3);
/// assert_eq!(
/// result,
/// vec![
/// Person { name: "Bob".to_string(), age: 30 },
/// Person { name: "Carol".to_string(), age: 35 },
/// ]
/// );
/// ```
pub fn slice<T>(collection: &[T], start: isize, end: isize) -> Vec<T>
where
T: Clone,
{
let size = collection.len() as isize;
// Adjust start index
let mut adjusted_start = if start < 0 { size + start } else { start };
if adjusted_start < 0 {
adjusted_start = 0;
}
if adjusted_start > size {
adjusted_start = size;
}
// Adjust end index
let mut adjusted_end = if end < 0 { size + end } else { end };
if adjusted_end < 0 {
adjusted_end = 0;
}
if adjusted_end > size {
adjusted_end = size;
}
// If start is greater than or equal to end, return empty vector
if adjusted_start >= adjusted_end {
return Vec::new();
}
// Convert to usize for slicing
let start_usize = adjusted_start as usize;
let end_usize = adjusted_end as usize;
collection[start_usize..end_usize].to_vec()
}
#[cfg(test)]
mod tests {
use super::*;
#[derive(Debug, PartialEq, Clone)]
struct Person {
name: String,
age: u32,
}
#[test]
fn test_slice_positive_indices_within_bounds() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, 1, 3);
assert_eq!(result, vec![2, 3]);
}
#[test]
fn test_slice_positive_indices_exceed_bounds() {
let numbers = vec![1, 2, 3];
let result = slice(&numbers, 1, 5);
assert_eq!(result, vec![2, 3]);
}
#[test]
fn test_slice_negative_start_within_bounds() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, -3, -1);
assert_eq!(result, vec![3, 4]);
}
#[test]
fn test_slice_negative_start_exceeds_bounds() {
let numbers = vec![1, 2, 3];
let result = slice(&numbers, -5, 2);
assert_eq!(result, vec![1, 2]);
}
#[test]
fn test_slice_negative_end_within_bounds() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, 1, -1);
assert_eq!(result, vec![2, 3, 4]);
}
#[test]
fn test_slice_negative_end_exceeds_bounds() {
let numbers = vec![1, 2, 3];
let result = slice(&numbers, 0, -5);
assert_eq!(result, Vec::<i32>::new());
}
#[test]
fn test_slice_start_greater_than_end() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, 4, 2);
assert_eq!(result, Vec::<i32>::new());
}
#[test]
fn test_slice_start_equals_end() {
let numbers = vec![1, 2, 3];
let result = slice(&numbers, 2, 2);
assert_eq!(result, Vec::<i32>::new());
}
#[test]
fn test_slice_full_range() {
let numbers = vec![1, 2, 3];
let result = slice(&numbers, 0, 3);
assert_eq!(result, vec![1, 2, 3]);
}
#[test]
fn test_slice_empty_collection() {
let empty: Vec<i32> = vec![];
let result = slice(&empty, 0, 3);
assert_eq!(result, Vec::<i32>::new());
}
#[test]
fn test_slice_with_structs() {
let people = vec![
Person {
name: "Alice".to_string(),
age: 25,
},
Person {
name: "Bob".to_string(),
age: 30,
},
Person {
name: "Carol".to_string(),
age: 35,
},
Person {
name: "Dave".to_string(),
age: 40,
},
];
let result = slice(&people, 1, 3);
assert_eq!(
result,
vec![
Person {
name: "Bob".to_string(),
age: 30
},
Person {
name: "Carol".to_string(),
age: 35
},
]
);
}
#[test]
fn test_slice_with_floats() {
let float_collection = vec![1.1, 2.2, 3.3, 4.4, 5.5];
let result = slice(&float_collection, -4, -1);
assert_eq!(result, vec![2.2, 3.3, 4.4]);
}
#[test]
fn test_slice_with_characters() {
let chars = vec!['a', 'b', 'c', 'd', 'e'];
let result = slice(&chars, 2, 4);
assert_eq!(result, vec!['c', 'd']);
}
#[test]
fn test_slice_with_overlapping_negative_indices() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, -4, -1);
assert_eq!(result, vec![2, 3, 4]);
}
#[test]
fn test_slice_full_negative_indices() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, -5, -1);
assert_eq!(result, vec![1, 2, 3, 4]);
}
#[test]
fn test_slice_partial_negative_indices() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, 1, -2);
assert_eq!(result, vec![2, 3]);
}
#[test]
fn test_slice_start_negative_end_positive() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, -3, 4);
assert_eq!(result, vec![3, 4]);
}
#[test]
fn test_slice_end_negative_start_positive() {
let numbers = vec![1, 2, 3, 4, 5];
let result = slice(&numbers, 1, -1);
assert_eq!(result, vec![2, 3, 4]);
}
}