Function compact 

pub fn compact<T: IsEmpty>(values: &mut Vec<T>)

🚮 Compacts a mutable vector by removing all elements that are considered “empty”.

This function iterates through the vector and retains only those elements for which the is_empty() method returns false.

Type Parameters

• T: The type of elements in the vector. Must implement the IsEmpty trait.

Arguments

• values: A mutable reference to the Vec<T> to be compacted.

Behavior

• Modifies the input vector in-place, removing elements for which is_empty() is true.
• If the vector is initially empty, it remains empty.
• If all elements are empty, the result is an empty vector.
• If no elements are empty, the vector remains unchanged.

Performance

• Runs in O(n) time, where n is the number of elements.
• Uses Vec::retain() under the hood — efficient, no reallocations.
• Each element is checked once. For types where is_empty() is O(1), overall cost is linear and very fast.

Supported Types

This function works with any type that implements the IsEmpty trait, such as:

• String, &str
• All integers and floats (0, 0.0 are “empty”)
• bool (false is “empty”)
• Vec<T> where T: IsEmpty
• Option<T> where T: IsEmpty

Examples

📜 Remove empty strings

use pencil_box::array::compact::compact;
use pencil_box::traits::IsEmpty;

let mut items = vec!["hello".to_string(), "".to_string(), "world".to_string()];
compact(&mut items);
assert_eq!(items, vec!["hello", "world"]);

📦 Remove empty vectors

let mut data = vec![vec![1], vec![], vec![2, 3]];
compact(&mut data);
assert_eq!(data, vec![vec![1], vec![2, 3]]);

🧹 Remove zero values

let mut nums = vec![0, 1, 0, 2, 3];
compact(&mut nums);
assert_eq!(nums, vec![1, 2, 3]);

❓ Remove None and empty Somes

let mut opts = vec![Some("hi"), None, Some("")];
compact(&mut opts);
assert_eq!(opts, vec![Some("hi")]);

🔍 Leave non-empty values untouched

let mut flags = vec![true, true, true];
compact(&mut flags);
assert_eq!(flags, vec![true, true, true]);

📭 No-op on empty input

let mut empty: Vec<String> = vec![];
compact(&mut empty);
assert!(empty.is_empty());