The num_traits API, but in prefix notation

What is this?

If you're trying to do scientific computing in Rust, and you can't get used to mathematical functions like sin() or cos() being postfix methods, this crate may be for you!

It provides free function versions of the trait methods of the num traits, so that you can easily do things like sin(x) + 3*ln(y).

Each trait's methods are exposed as an module of free functions, named after a snake_case version of the trait's name, and it only takes a couple of use clauses to go from there to using the above syntax in your math expressions.

Only a one-line summary of each method's documentations is provided, please refer to the corresponding trait method's documentation in num_traits for the full details of each function's API contract.

Note that one advantage of the num_traits' trait-based approach over free functions is that trait methods gracefully handle namespace collisions. Whereas with this crate, you will be the one responsible for use-ing the right methods for a given task. For what it's worth, this is why programming languages with prefix numerical methods usually also support method overloading, which Rust could not support as it would break the kind of advanced type inference that all Rustaceans are used to enjoy.

API coverage

This crate generally opts for maximal coverage of the num traits, except in the following circumstances:

• The trait represents an operator whose standard notation is closer to a postfix method than to a prefix function, as is the case for most binary operators. For this reason, AsPrimitive, CheckedAdd, CheckedDiv, CheckedMul, CheckedRem, CheckedShl, CheckedShr, CheckedSub, MulAdd, MulAddAssign, Saturating, WrappingAdd, WrappingMul, WrappingShl, WrappingShr and WrappingSub are not covered.
• The num_trait crate already provides a set of free functions that cover 90% of a trait's functionality, and we re-export them. Thus, One, Signed and Zero are not covered.
• A specific trait or its methods would require very significant supporting infrastructure to be exposed as a free function by this crate, and the extent of its real-world usage does not seem to justify the effort. To be more specific...
  • FloatConst::TAU() would require adding Self trait bound support to the underlying macro infrastructure, while TAU is arguably a math expert joke that most normal persons would spell out as 2.0 * PI.
  • MulAdd and MulAddAssign would require adding generic trait support to the underlying macro infrastructure, while it is debatable whether a multiply-add should be considered a prefix or postfix operator.
  • NumCast would require adding generic trait method support, when it is dubious whether from::<T, _>(n) is actually a readability improvement over the T::from(n) that it replaces.
  • i128-based casts would require extending this crate's conditional compilation setup quite a bit through use of the autocfg crate, which seems to be a bit much considering how obscure that type is.

If you find a num trait functionality which is neither exposed by this crate nor covered by the above list, this is likely an oversight from my part, please ping me about it.

I am also willing to reconsider any point of the above policy if someone manages to make a good argument against it. Issues are welcome!

License

This crate is distributed under the terms of the MPLv2 license. See the LICENSE file for details.

More relaxed licensing (Apache, MIT, BSD...) may also be negociated, in exchange of a financial contribution. Contact me for details at knightsofni AT gmx DOTCOM.