rust泛型初始化成0
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2020-09-04 00:02:25
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std::num::Int被deprecated了。所以只能用别人的crate或者自己实现Zero了。
github上有一个不错的：
https://github.com/rust-num/num-traits
有关Zero的部分：
pub trait Zero {
fn zero() -> Self;
fn is_zero(&self) -> bool;
}
macro_rules! zero_impl {
($t:ty, $v:expr) => {
impl Zero for $t {
#[inline]
fn zero() -> $t {
$v
}
#[inline]
fn is_zero(&self) -> bool {
*self == $v
}
}
};
}
zero_impl!(usize, 0);
zero_impl!(u8, 0);
zero_impl!(u16, 0);
zero_impl!(u32, 0);
zero_impl!(u64, 0);
#[cfg(has_i128)]
zero_impl!(u128, 0);
zero_impl!(isize, 0);
zero_impl!(i8, 0);
zero_impl!(i16, 0);
zero_impl!(i32, 0);
zero_impl!(i64, 0);
#[cfg(has_i128)]
zero_impl!(i128, 0);
zero_impl!(f32, 0.0);
zero_impl!(f64, 0.0);
|
把这段复制一下就可以用
Zero trait了。
示例：
pub trait Zero {
fn zero() -> Self;
fn is_zero(&self) -> bool;
}
macro_rules! zero_impl {
($t:ty, $v:expr) => {
impl Zero for $t {
#[inline]
fn zero() -> $t {
$v
}
#[inline]
fn is_zero(&self) -> bool {
*self == $v
}
}
};
}
zero_impl!(usize, 0);
zero_impl!(u8, 0);
zero_impl!(u16, 0);
zero_impl!(u32, 0);
zero_impl!(u64, 0);
#[cfg(has_i128)]
zero_impl!(u128, 0);
zero_impl!(isize, 0);
zero_impl!(i8, 0);
zero_impl!(i16, 0);
zero_impl!(i32, 0);
zero_impl!(i64, 0);
#[cfg(has_i128)]
zero_impl!(i128, 0);
zero_impl!(f32, 0.0);
zero_impl!(f64, 0.0);
fn print<T: Zero + std::fmt::Display + std::clone::Clone>(x: T) {
println!("{}", x);
let test = vec![T::zero(); 10];
for x in test.iter() {
println!("{}", x);
}
}
fn main() {
print(233);
print(233.0);
}
|
输出：
233
0
0
0
0
0
0
0
0
0
0
233
0
0
0
0
0
0
0
0
0
0
|