Trait alloc::fmt::UpperHex

1.0.0 · source · [−]

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

Expand description

X formatting.

The UpperHex trait should format its output as a number in hexadecimal, with A through F in upper 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 x = 42; // 42 is '2A' in hex

assert_eq!(format!("{x:X}"), "2A");
assert_eq!(format!("{x:#X}"), "0x2A");

assert_eq!(format!("{:X}", -16), "FFFFFFF0");

Run

Implementing UpperHex on a type:

use std::fmt;

struct Length(i32);

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

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

let l = Length(i32::MAX);

assert_eq!(format!("l as hex is: {l:X}"), "l as hex is: 7FFFFFFF");

assert_eq!(format!("l as hex is: {l:#010X}"), "l as hex is: 0x7FFFFFFF");