This crate provides a
Vec<N, A> type, which wraps the standard
and tracks its size
N at the type level.
Because the size is embedded in the type, we can do things like verifying at compile time that index lookups are within bounds.
let vec = svec![1, 2, 3]; // This index lookup won't compile, because index `U8` is outside // the vector's length of `U3`: assert_eq!(5, vec[U8::new()]);
let vec = svec![1, 2, 3]; // On the other hand, this lookup can be verified to be correct // by the type system: assert_eq!(3, vec[U2::new()]);
If this looks too good to be true, it's because it comes with a number of
limitations: you won't be able to perform operations on the vector which
could leave it with a length that can't be known at compile time. This
Extend::extend() and filtering operations like
FromIterator::from_iter is, notably, also not available, but you can use
Vec::try_from as a replacement. Note that
try_from needs to be able to
infer the size of the resulting vector at compile time; there's no way to
construct a vector of arbitrary length.
let vec = svec![1, 2, 3, 4, 5]; let new_vec = Vec::try_from(vec.into_iter().map(|i| i + 10)); assert_eq!(Some(svec![11, 12, 13, 14, 15]), new_vec);
A type level range.
A vector of length