In this commit I added a useful utility type, named Void, that encapsulates the
doable but annoying job of creating an uninhabited type. As well, a function on
that type, named absurd, was created which is useful for ignoring the result of
matching on that type. No unit tests were created because it is not possible to
create an instance of this type to test the usage of.
This type is useful because it is like NonCopyable in that it can be used to
create a type with special characteristics without special bloat. For instance,
instead of typing pub struct PhantomType { priv contents : () } for each void
type one may want to use one can simply type pub struct PhantomType (Void);.
This type make such special cases much easier to write.
At the moment this only includes type checking and there is no code generation support yet. I wanted to get the design reviewed first.
From discussion with @graydon at #5841, re-implemented as `#[simd]` attribute on structs.
Progressing towards #3499.
This is part of the redesign of the numeric traits tracked in issue #4819.
Renamed:
- `Exponential::expm1` -> `Float::exp_m1` - for consistency with underscore usage elsewhere
- `Exponential::log` -> `Exponential::ln` - a less ambiguous name for the natural logarithm
- `{float, f64, f32}::logarithm` -> `Exponential::log` - for arbitrary base logarithms
- `Real::log_2` -> `Real::ln_2` - for consistency with `ln`
- `Real::log_10` -> `Real::ln_10` - for consistency with `ln`
Added:
- `Signed::abs_sub` - wraps libm's `fdim` function
- `Float::is_normal` - returns `true` if the number is neither zero, infinite, subnormal or NaN
- `Float::classify` - returns the floating point category of the number
- `Float::ln_1p` - returns the natural logarithm of the number plus one
@brson: r? [please ignore the other one that was accidentally based off master due to back-button-bugs in github.com]
My goal is to resolve the question of whether we want to encourage (by example) consistent use of pub to make identifiers publicly-accessible, even in syntax extensions. (If people don't want that, then we can just let this pull request die.)
This is part one of two. Part two, whose contents should be clear from the FIXME's in this commit, would land after this gets incorporated into a snapshot.
(The eventual goal is to address issue #6009 , which was implied by my choice of branch name, but not mentioned in the pull request, so github did not notice it.)
Both expm1 and ln1p have been renamed to exp_m1 and ln_1p in order to be consistent with the underscore usage elsewhere.
The exp_m1 method is used for increased accuracy when doing floating point calculations, so this has been moved from the more general 'Exponential' trait into 'Float'.
