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// devela::num::sign
//
//! the sign of a number.
//
// TOC
// - definition
// - impl Into Sign
// - impl (Try)From Sign
use crate::{
ConstDefault,
NumError::{self, Invalid},
NumResult as Result,
};
/// Represents the sign of a number.
#[must_use]
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
pub enum Sign {
/// A negative sign (-).
Negative = -1,
/// An absence of sign, associated with Zero. (The default)
#[default]
None = 0,
/// A positive sign (+).
Positive = 1,
}
impl ConstDefault for Sign {
/// No sign.
const DEFAULT: Self = Sign::None;
}
/* Into Sign */
// helper macro to implement conversion from numbers to Sign
macro_rules! impl_into_sign {
// integer primitives
(int: $($int:ty),+) => { $( impl_into_sign![@int: $int]; )+ };
(@int: $int:ty) => {
impl From<$int> for Sign {
/// Returns `None` if 0, `Positive` if > 0 and `Negative` if < 0.
fn from(n: $int) -> Sign {
match n {
0 => Sign::None,
1.. => Sign::Positive,
#[allow(unreachable_patterns, reason = "for unsigned")]
_ => Sign::Negative,
}
}
}
};
// floating-point primitives
(float: $($float:ty),+) => { $( impl_into_sign![@float: $float]; )+ };
(@float: $float:ty) => {
impl From<$float> for Sign {
/// Returns `None` if 0.0, `Positive` if > 0 and `Negative` if < 0.
fn from(n: $float) -> Sign {
if n.is_sign_positive() {
Sign::Positive
} else {
Sign::Negative
}
}
}
};
// boolean primitive
(bool) => {
impl From<bool> for Sign {
/// Returns `Positive` if `true` and `Negative` if `false`.
fn from(n: bool) -> Sign {
match n {
true => Sign::Positive,
false => Sign::Negative,
}
}
}
};
}
impl_into_sign![int: u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize];
impl_into_sign![float: f32, f64];
impl_into_sign![bool];
/* (Try)From Sign */
// helper macro to implement conversion from Sign to numbers (1, 0, -1)
macro_rules! impl_from_sign {
// signed integer primitives
(sint: $($sint:ty),+) => { $( impl_from_sign![@sint: $sint]; )+ };
(@sint: $sint:ty) => {
impl From<Sign> for $sint {
/// Returns 0 if `None`, 1 if `Positive` and -1 if `Negative`.
fn from(s: Sign) -> $sint {
match s {
Sign::None => 0,
Sign::Positive => 1,
Sign::Negative => -1,
}
}
}
};
// unsigned integer primitives
(uint: $($uint:ty),+) => { $( impl_from_sign![@uint: $uint]; )+ };
(@uint: $uint:ty) => {
impl TryFrom<Sign> for $uint {
type Error = NumError;
/// Returns 0 if `None` and 1 if `Positive`.
///
/// # Errors
/// Returns [`Invalid`] if the sign is `Negative`.
fn try_from(s: Sign) -> Result<$uint> {
match s {
Sign::None => Ok(0),
Sign::Positive => Ok(1),
Sign::Negative => Err(Invalid),
}
}
}
};
// floating-point primitives
(float: $($float:ty),+) => { $( impl_from_sign![@float: $float]; )+ };
(@float: $float:ty) => {
impl From<Sign> for $float {
/// Returns 0.0 if `None`, 1.0 if `Positive` and -1.0 if `Negative`.
fn from(s: Sign) -> $float {
match s {
Sign::None => 0.0,
Sign::Positive => 1.0,
Sign::Negative => -1.0,
}
}
}
};
// boolean primitive
(bool) => {
impl TryFrom<Sign> for bool {
type Error = NumError;
/// Returns `true` if `None` and `false` if `Negative`.
///
/// # Errors
/// Returns [`Invalid`] if the sign is `None`.
fn try_from(s: Sign) -> Result<bool> {
match s {
Sign::Positive => Ok(true),
Sign::Negative => Ok(false),
Sign::None => Err(Invalid),
}
}
}
};
}
impl_from_sign![sint: i8, i16, i32, i64, i128, isize];
impl_from_sign![uint: u8, u16, u32, u64, u128, usize];
impl_from_sign![float: f32, f64];
impl_from_sign![bool];