LowerExp in core::fmt - Rust
Description: `e` formatting.

# Trait LowerExp

1.6.0 · Source

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

Expand description

`e` formatting.

The `LowerExp` trait should format its output in scientific notation with a lower-case `e`.

For more information on formatters, see the module-level documentation.

## §Examples

Basic usage with `f64`:

    let x = 42.0; // 42.0 is '4.2e1' in scientific notation

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

Implementing `LowerExp` on a type:

    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) // delegate to f64's implementation
        }
    }

    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"
    );

## Required Methods§

1.0.0 · Source

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

Formats the value using the given formatter.

##### §Errors

This function should return `Err` if, and only if, the provided `Formatter` returns `Err`. String formatting is considered an infallible operation; this function only returns a `Result` because writing to the underlying stream might fail and it must provide a way to propagate the fact that an error has occurred back up the stack.

## Implementors§

1.0.0 · Source§

### impl LowerExp for f32

1.0.0 · Source§

### impl LowerExp for f64

1.42.0 · Source§

### impl LowerExp for i8

1.42.0 · Source§

### impl LowerExp for i16

1.42.0 · Source§

### impl LowerExp for i32

1.42.0 · Source§

### impl LowerExp for i64

1.42.0 · Source§

### impl LowerExp for i128

1.42.0 · Source§

### impl LowerExp for isize

1.42.0 · Source§

### impl LowerExp for u8

1.42.0 · Source§

### impl LowerExp for u16

1.42.0 · Source§

### impl LowerExp for u32

1.42.0 · Source§

### impl LowerExp for u64

1.42.0 · Source§

### impl LowerExp for u128

1.42.0 · Source§

### impl LowerExp for usize

1.84.0 · Source§

### impl<T> LowerExp for NonZero<T>
where T: ZeroablePrimitive + LowerExp,

1.0.0 · Source§

### impl<T: ?Sized + LowerExp> LowerExp for &T

1.0.0 · Source§

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