# Trait core::fmt::Binary

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

`b` formatting.

The `Binary` trait should format its output as a number in binary.

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

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

## §Examples

Basic usage with `i32`:

``````let x = 42; // 42 is '101010' in binary

assert_eq!(format!("{x:b}"), "101010");
assert_eq!(format!("{x:#b}"), "0b101010");

assert_eq!(format!("{:b}", -16), "11111111111111111111111111110000");``````
Run

Implementing `Binary` on a type:

``````use std::fmt;

struct Length(i32);

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

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

let l = Length(107);

assert_eq!(format!("l as binary is: {l:b}"), "l as binary is: 1101011");

assert_eq!(
// Note that the `0b` prefix added by `#` is included in the total width, so we
// need to add two to correctly display all 32 bits.
format!("l as binary is: {l:#034b}"),
"l as binary is: 0b00000000000000000000000001101011"
);``````
Run

## Required Methods§

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

Formats the value using the given formatter.

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