如何在不重复的情况下以相同的方式为多种类型实现特征？

Question

鉴于一个特征,我们可能希望为许多类型实现它.

pub trait RTypeUnit {
    fn zero() -> Self;
    fn one() -> Self;
}

impl RTypeUnit for usize { fn zero() -> usize { 0 } fn one() -> usize { 1 } }
impl RTypeUnit for isize { fn zero() -> isize { 0 } fn one() -> isize { 1 } }
impl RTypeUnit for u64 { fn zero() -> u64 { 0 } fn one() -> u64 { 1 } }
impl RTypeUnit for i64 { fn zero() -> i64 { 0 } fn one() -> i64 { 1 } }
impl RTypeUnit for u32 { fn zero() -> u32 { 0 } fn one() -> u32 { 1 } }
impl RTypeUnit for i32 { fn zero() -> i32 { 0 } fn one() -> i32 { 1 } }
impl RTypeUnit for u16 { fn zero() -> u16 { 0 } fn one() -> u16 { 1 } }
impl RTypeUnit for i16 { fn zero() -> i16 { 0 } fn one() -> i16 { 1 } }
impl RTypeUnit for u8 { fn zero() -> u8 { 0 } fn one() -> u8 { 1 } }
impl RTypeUnit for i8 { fn zero() -> i8 { 0 } fn one() -> i8 { 1 } }

避免为每种类型写出函数的惯用方法是什么？我应该使用默认实现,还是宏？

我知道num这些特定方法的箱子,但我很想知道如何在一般情况下这样做.

Answer 1

根据Rust参考:

实现是实现特定类型的特征的项.

看看的实现Zero,并One在文档(因为锈1.11过时了,我删除了简洁的废弃属性):

pub trait Zero: Sized {
    fn zero() -> Self;
}

pub trait One: Sized {
    fn one() -> Self;
}

macro_rules! zero_one_impl {
    ($($t:ty)*) => ($(
        impl Zero for $t {
            #[inline]
            fn zero() -> Self { 0 }
        }
        impl One for $t {
            #[inline]
            fn one() -> Self { 1 }
        }
    )*)
}
zero_one_impl! { u8 u16 u32 u64 usize i8 i16 i32 i64 isize }

如果标准文档用宏做了,我怀疑是否存在更好的方法.