313: Scalar operations across all integer types r=cuviper
With my apologies for opening a new PR, and also for the 8 month delay, this continues the work started in #237 - the discussion there outlines the goals I was aiming for. I suppose this supersedes that PR and the other one can now be closed.
This PR adds support for Add, Sub, Mul, Div and Rem operations involving one BigInt/BigUint and one primitive integer, with operands in either order, and any combination of owned/borrowed arguments.
A BigUint can be divided by a BigDigit - this is one of several
operations being implemented to allow scalar operations on BigInt and
BigUint across the board.
A BigDigit can be subtracted from a BigUint - this is one of several
operations being implemented to allow scalar operations on BigInt and
BigUint across the board.
A BigDigit can be added to a BigUint - this is one of several
operations being implemented to allow scalar operations on BigInt and
BigUint across the board.
- rename `_twos_complement_` methods to just `_signed_`
- make `from_` variants take &[u8]
- refactor helper functions twos_complement (they take byte slice but use a generic function underneath)
- fix issues in `to_signed_` functions (only two's complement negative numbers; perform byte extension where needed)
- add tests to `to_signed_` methods
- The CI script now tests them all with --no-default-features.
- bigint: testing needs rand even when the main feature is disabled.
- rational: gate `FromPrimitive for Ratio<BigInt>` on having bigint.
`DefaultHasher` wasn't stable until 1.13, at which point all the other
hashers were deprecated, so it's not easy for us to name a hasher type
to use for testing. However, `RandomState` has been stable since 1.7,
and it implements `BuildHasher` that has a `Hasher` associated type.
If a `+` is encountered in the middle of parsing a BigUint, this should
generate an `ParseIntError::InvalidDigit`. Since we can't create that
directly, we get it by trying to parse a `u64` from this point, but of
course `+` is a perfectly valid prefix to a `u64`.
Now we include the previous character in the string passed to `u64`, so
it has proper parsing context to understand what's in error.
Fixes#268.
Nicolas Kirchner
Josh Stone
bors[bot]
Keith Wansbrough
Sam Cappleman-Lynes
Eduardo Pinho
Phaiax
Patrick Jackson
bluss