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## LowerHex

# Trait LowerHex

1.36.0 · Source

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

Expand description

`x` formatting.

The `LowerHex` trait should format its output as a number in hexadecimal, with `a` through `f` in lower case.

For primitive signed integers (`i8` to `i128`, and `isize`), negative values are formatted as the two’s complement representation.

The alternate flag, `#`, adds a `0x` in front of the output.

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

## §Examples

Basic usage with `i32`:

    let y = 42; // 42 is '2a' in hex

    assert_eq!(format!("{y:x}"), "2a");
    assert_eq!(format!("{y:#x}"), "0x2a");

    assert_eq!(format!("{:x}", -16), "fffffff0");

Implementing `LowerHex` on a type:

    use std::fmt;

    struct Length(i32);

    impl fmt::LowerHex for Length {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            let val = self.0;

            fmt::LowerHex::fmt(&val, f) // delegate to i32's implementation
        }
    }

    let l = Length(9);

    assert_eq!(format!("l as hex is: {l:x}"), "l as hex is: 9");

    assert_eq!(format!("l as hex is: {l:#010x}"), "l as hex is: 0x00000009");

## Required Methods§

1.0.0 · Source

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

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.

## Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

## Implementors§

1.0.0 · Source§

### impl LowerHex for i8

1.0.0 · Source§

### impl LowerHex for i16

1.0.0 · Source§

### impl LowerHex for i32

1.0.0 · Source§

### impl LowerHex for i64

1.0.0 · Source§

### impl LowerHex for i128

1.0.0 · Source§

### impl LowerHex for isize

1.0.0 · Source§

### impl LowerHex for u8

1.0.0 · Source§

### impl LowerHex for u16

1.0.0 · Source§

### impl LowerHex for u32

1.0.0 · Source§

### impl LowerHex for u64

1.0.0 · Source§

### impl LowerHex for u128

1.0.0 · Source§

### impl LowerHex for usize

1.0.0 · Source§

### impl<T> LowerHex for &T
where T: LowerHex + ?Sized,

1.0.0 · Source§

### impl<T> LowerHex for &mut T
where T: LowerHex + ?Sized,

1.28.0 · Source§

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

1.74.0 · Source§

### impl<T> LowerHex for Saturating<T>
where T: LowerHex,

1.11.0 · Source§

### impl<T> LowerHex for Wrapping<T>
where T: LowerHex,