Currently the types in the block module have longer names than
necessary, "header" and "version" identifiers contain the word "block",
this is unnecessary because we can write `block::Header` instead of
`BlockHeader` when context is required. This allows us to use the naked
type `Header` inside the `block` module with no loss of clarity.
We are stuck with `BlockHash` because the type is defined along with all
the other hash types in `hash_types`, leave it as is for now but
re-export it from the `block` module to assist in putting types that are
used together in scope in the same place, making import statements more
ergonomic.
A zero default value for `Target` and `Work` has no significance and/or
usecase, remove the derived `Default` implementation.
Includes making `Target::ZERO` public.
Currently we use the `Uint256` type to represent two proof of work
integers, namely target and difficulty (work).
It would be nice to not have a public integer type that is not fully
implemented (i.e., does not implement arithmetic etc as do integer types
in stdlib). Instead of implementing all the stdlib functions we can
instead add two new wrapper types, since these are not general purpose
integers they do not need to implement anything we do not need to use.
- Add a `pow` module.
- Put a modified version of `Uint256` to `pow`.
- Add two new wrapper types `Target` and `Difficulty`.
- Only implement methods that we use on each type.
Note this patch does not remove the original `Uint256`, that will be
done as a separate patch.
Tobin C. Harding