another-option 0.1.1

Another option data type; useful when allocations are expensive.
Documentation
  • Coverage
  • 28.57%
    6 out of 21 items documented1 out of 21 items with examples
  • Size
  • Source code size: 12.72 kB This is the summed size of all the files inside the crates.io package for this release.
  • Documentation size: 1.74 MB This is the summed size of all files generated by rustdoc for all configured targets
  • Links
  • xpe/another-option
    0 0 1
  • crates.io
  • Dependencies
    • —
  • Versions
  • Owners
  • xpe

another-option

This package provides Opt<T> as an alternative to Option<T>. Why would you want another option? Opt provides advantages when:

  1. the generic type, T, is expensive to allocate, and
  2. mutation between None and Some(...) is frequent.

Examples

Since Rust's built-in Option<T> is an enum, it will drop its Some(...) value when None is assigned.

let mut option: Option<String> = Some(String::with_capacity(1024));
option = None; // drops the string
option = Some(String::with_capacity(1024)); // allocation

Since Opt<T> always owns the value, even when empty, the value can be reused without drops or allocations:

use crate::another_option::Opt;
let mut opt: Opt<String> = Opt::some(String::with_capacity(1024));
opt.map_in_place(|v| v.push_str("value"));
opt.set_none(); // does *not* drop the string
opt.set_some();
assert_eq!(opt.unwrap(), String::from("value"));