Trait CollectVector

pub trait CollectVector: Iterator {
    // Provided methods
    fn collect_vec_with<F>(self, capacity: F) -> Vec<Self::Item>
       where F: FnOnce(usize) -> usize,
             Self: Sized { ... }
    fn collect_vec_with_exact<F>(self, capacity: F) -> Vec<Self::Item>
       where F: FnOnce(usize) -> usize,
             Self: Sized { ... }
}

Available on crate feature collect_vec only.

Trait providing enhanced vector collection strategies for iterators.

Essentially, it calls the CollectWith trait, simplifying .collect_with::<Vec<_>>() to .collect_vec_with().

Extends iterators with methods for collecting items into a Vec with customizable capacity pre-allocation strategies.

Provided Methods

fn collect_vec_with<F>(self, capacity: F) -> Vec<Self::Item>

where F: FnOnce(usize) -> usize, Self: Sized,

Collect iterator elements into a Vec with capacity calculation.

• capacity:
  • Closure that calculates capacity based on iterator size hints.
• |size_bound|: max(lower_bound, upper_bound) from the iterator’s size_hint()

About the Final Capacity Size

For example, (0..10).collect_vec_with(|_size_bound| 2):

1. (0..10).size_hint() returns (10, Some(10)).
2. _size_bound is 10.
3. The closure returns 2, the final capacity is max(10, 2) = 10.
4. The vector is created with Vec::with_capacity(10).

If you need an exact capacity size, please use .collect_vec_with_exact()

Example

use collect_with::CollectVector;

let nums = (0..10).collect_vec_with(|size_bound| size_bound + 2);
assert_eq!(nums.capacity(), 12);

Suitable when the exact element count is unknown but better-than-default pre-allocation is desired.

fn collect_vec_with_exact<F>(self, capacity: F) -> Vec<Self::Item>

where F: FnOnce(usize) -> usize, Self: Sized,

Collect iterator elements into a Vec with exact capacity calculation.

Example

use collect_with::CollectVector;

let _nums = (0..10)
  .collect_vec_with_exact(|size_bound| match size_bound {
    0 => 32,
    u => u,
});

Preferred when iterator provides exact size information via size_hint() and precise allocation is critical.

Implementors

impl<I: Iterator> CollectVector for I

Blanket implementation for iterators to add vector collection capabilities.

Provides collect_vec_with() and collect_vec_with_exact() methods