Type Parameters

bitvec uses type parameters to permit precise user control of its behavior and in-memory representation. The Rust generic system permits bitvec to have a more powerful and capable behavior than any other bitstream library yet implemented in any language.

All bitvec types take two type parameters:

1. T: the storage type. The slice types (BitSlice, BitVec, BitBox) select an unsigned integer, since as slices they store the length in their runtime state. BitArray uses either a bare integer or an integer array as its storage parameter, since it has no runtime state of its own and stores all of its information in the type system.
2. O: the ordering of bits within a single T element. We provide two orderings, Msb0 and Lsb0.

The combination of these two type parameters governs how bitvec translates its abstract storage (usize -> bool) into real memory; if you do not care about real-memory representation, then the default type parameters <usize, Lsb0> will give you the best performance. If you do care about this, then the memory representation chapter goes into detail about all the combinations and can help you select which one best fits your needs.

The BitOrder trait is open for third-party implementation. It describes its requirements in great detail in its API documentation, so if you have a memory representation that is neither Lsb0 nor Msb0, you can implement the ordering yourself and bitvec will use it without complaint.

Rust syntax requires explicitly choosing type parameters when using generic expressions, such as BitVec::<Store, Order>::new(), and will not substitute in the default parameters when attempting to elide the parameters with BitVec::new(). However, Rust will use the default type parameters in patterns: let bv: BitVec = BitVec::new(); will use the default type parameters in the : BitVec type annotation, which then completes the type of the expression on the right side of the assignment =.