alloc::fmt

# Trait Octal

1.36.0 · Source

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

Expand description

`o` formatting.

The `Octal` trait should format its output as a number in base-8.

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

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

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

## §Examples

Basic usage with `i32`:

    let x = 42; // 42 is '52' in octal

    assert_eq!(format!("{x:o}"), "52");
    assert_eq!(format!("{x:#o}"), "0o52");

    assert_eq!(format!("{:o}", -16), "37777777760");

Implementing `Octal` on a type:

    use std::fmt;

    struct Length(i32);

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

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

    let l = Length(9);

    assert_eq!(format!("l as octal is: {l:o}"), "l as octal is: 11");

    assert_eq!(format!("l as octal is: {l:#06o}"), "l as octal is: 0o0011");

## 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.

## Implementors§

1.0.0 · Source§

### impl Octal for i8

1.0.0 · Source§

### impl Octal for i16

1.0.0 · Source§

### impl Octal for i32

1.0.0 · Source§

### impl Octal for i64

1.0.0 · Source§

### impl Octal for i128

1.0.0 · Source§

### impl Octal for isize

1.0.0 · Source§

### impl Octal for u8

1.0.0 · Source§

### impl Octal for u16

1.0.0 · Source§

### impl Octal for u32

1.0.0 · Source§

### impl Octal for u64

1.0.0 · Source§

### impl Octal for u128

1.0.0 · Source§

### impl Octal for usize

1.0.0 · Source§

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

1.0.0 · Source§

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

1.28.0 · Source§

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

1.74.0 · Source§

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

1.11.0 · Source§

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