Arithmetic-sign

Arithmetic Sign(≈+1|-1) to/from arithmetic types such as f64, i32 utility.

Feature

• From and TryFrom: An arithmetic type such as f64, i32 =(from/try_from)> Sign
  • From: For an integral such as i32.; It has no infinite pattern.
  • TryFrom: For an float such as f64.; It has +inf, -inf and NaN infinite patterns.
    • A finite, +inf, -inf are valid => Ok, nan is invalid => Err.
• as_T: Sign =(as_T)> an arithmetic type such as f64, i32
  • as_uT: Safety unsigned casting. eg. pos => Ok, neg => Err
• Display: Sign =(to_string)> "-" or "+"
  • Sign =(to_string_specified("S", "N"))> "S" or "N"
• Mul and Div: Sign * Sign or Sign / Sign -> Sign; eg. neg * neg => pos, pos / neg => neg
• Neg and Not: -Sign or !Sign -> Sign; eg. -neg => pos, !pos => neg
• Eq: Sign ==|!= Sign; eg. neg == neg => true, pos != neg => true
• Ord: Sign <|<=|>=|> Sign; eg. neg < pos => true, pos >= pos => true, neg > pos => false

Usage

• See also: tests/test.rs.

use arithmetic_sign::*;

let _sign = Sign::from( 123 ); // -> Sign::Positive
let _sign = Sign::from( 0 ); // -> Sign::Positive
let _sign = Sign::from( -0 ); // -> Sign::Positive
let _sign = Sign::from( -123 ); // -> Sign::Negative
let _sign_maybe = Sign::try_from( 1.23 ); // -> Ok( Sign::Positive )
let _sign_maybe = Sign::try_from( 0.0 ); // -> Ok( Sign::Positive )
let _sign_maybe = Sign::try_from( -0.0 ); // -> Ok( Sign::Positive )
let _sign_maybe = Sign::try_from( 1.23 ); // -> Ok( Sign::Negative )
let _sign_maybe = Sign::try_from( std::f64::inf() ); // -> Ok( Sign::Positive )
let _sign = Sign::from( -123 ) * Sign::from( 123 ); // -> Sign::Negative
let _sign = !Sign::from( -123 ); // -> Sign::Positive
let _f64 = Sign::Positive.as_f64(); // 1f64
let _i32 = Sign::Negative.as_i32(); // -1i32
let _u8 = Sign::Positive.as_u8().unwrap(); // 1u8
let _u8 = Sign::Negative.as_u8().is_err(); // true

Motivation

• The std sign features such as std::{f32|f64}::copysign or std::*::signums are regard to negative from -0.0.
  • But, I author wanted to regard to "not a negative" as "positive" from 0.0 and -0.0.
  • And, I author wanted to boolean-like type such as "positive" and "negative" that has only 2-variant.
  • And, Infinity is a valid signed value, NaN is not a valid value.

License

• MIT

Author

• USAGI.NETWORK / Usagi Ito