Crate map_in_place

Reuse alloations when mapping the elements of a Vec, Box<[T]> or Box<T> if possible.

To map in place the types must have identical alignment and:

• for boxes and boxed slices the sizes must be equal,
• for vectors the size of in must be a multiple of the out type. so out cannot be bigger than in)

The ..._in_place() methods will panic if not possible, while the others will fall back to iterating and collecting.

I might add methods to the traits without a default impl or a major version bump; implement them for other types at your own risk.

Examples:

extern crate map_in_place;
use map_in_place::MapVecInPlace;
fn main() {
    let v = vec![8_u32,29,14,5];
    let v = v.filter_map(|n| if n < 10 {Some( (n as u8+b'0') as char)}
                             else      {None}
                        );// happens in place
    assert_eq!(&v, &['8','5']);
    let v = v.map(|c| c as u8);// falls back to iterators
    assert_eq!(&v[..], &b"85"[..]);
}

Traits

MapBoxInPlace
MapSliceInPlace
MapVecInPlace