Trait std::fmt::LowerExp

1.0.0 · source ·
pub trait LowerExp {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}
Expand description

e 格式。

LowerExp trait 应该使用小写的 e 以科学计数法格式化其输出。

有关格式化程序的更多信息,请参见 模块级文档

Examples

f64 的基本用法:

let x = 42.0; // 42.0 是 '4.2e1' 的科学计数形式

assert_eq!(format!("{x:e}"), "4.2e1");
Run

在类型上实现 LowerExp

use std::fmt;

struct Length(i32);

impl fmt::LowerExp for Length {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let val = f64::from(self.0);
        fmt::LowerExp::fmt(&val, f) // 委托 f64 的实现
    }
}

let l = Length(100);

assert_eq!(
    format!("l in scientific notation is: {l:e}"),
    "l in scientific notation is: 1e2"
);

assert_eq!(
    format!("l in scientific notation is: {l:05e}"),
    "l in scientific notation is: 001e2"
);
Run

Required Methods§

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

使用给定的格式化程序格式化该值。

Implementors§

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impl LowerExp for f32

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impl LowerExp for f64

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impl LowerExp for i8

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impl LowerExp for i16

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impl LowerExp for i32

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impl LowerExp for i64

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impl LowerExp for i128

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impl LowerExp for isize

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impl LowerExp for u8

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impl LowerExp for u16

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impl LowerExp for u32

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impl LowerExp for u64

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impl LowerExp for u128

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impl LowerExp for usize

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impl<T> LowerExp for &Twhere T: LowerExp + ?Sized,

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impl<T> LowerExp for &mut Twhere T: LowerExp + ?Sized,