index_vec
Note: API still unstable during 0.0.x
A more type-safe version of using Vec
, for when usize
s are getting you down.
This crate lets you define "newtype"-style wrappers around usize
(or other
integers), and Vec<T>
so that some additional type safety can be gained at
zero runtime cost.
Example / Overview
use ;
define_index_type!
// Create a vector which can be accessed using `StrIdx`s.
let mut strs: = index_vec!;
// l is a `StrIdx`
let l = strs.last_idx;
assert_eq!;
let new_i = strs.push;
assert_eq!;
// Indices are mostly interoperable with `usize`, and support
// a lot of what you might want to do to an index. (Note that
// it does *not* support these with other index wrappers --
// that seems too likely to lead to bugs).
// Comparison
assert_eq!;
// Addition
assert_eq!;
// Subtraction (Note that by default, the index will panic on overflow,
// but that can be configured in the macro)
assert_eq!;
// Wrapping
assert_eq!;
// ...
Background
The goal is to replace the pattern of using a type FooIdx = usize
to access a
Vec<Foo>
with something that can statically prevent using a FooIdx
in a
Vec<Bar>
. It's most useful if you have a bunch of indices referring to
different sorts of vectors.
Much of the code for this is taken from rustc
's IndexVec
code, however it's
diverged a decent amount at this point. The largest differences are:
- No usage of unstable features.
- Different syntax for defining index types.
- Allows use of index types beyond
u32
(usize
,u32
,u16
, andu8
are all supported). - More flexible behavior around how strictly some checks are performed.
Other crates
The indexed_vec
crate predates this,
and is a much closer copy of the code from rustc
. Unfortunately, this means it
does not compile on stable.
If you're looking for something further from a vec and closer to a map, you might find handy
, slotmap
, or slab
to be closer what you want.
License
This is based on code from rustc
's source, and retains it's status as
dual-licensed under MIT (LICENSE-MIT) / Apache 2.0 (LICENSE-APACHE).