^=Operator

Explanation

^= assigns the bitwise XOR of the left and right operands in place, overloadable via std::ops::BitXorAssign. A classic use is toggling bits: flags ^= mask flips exactly the bits set in mask.

Usage examples

Toggling bits in place

let mut flags = 0b1010u8;
flags ^= 0b0011; // <- toggles the bits set in the mask, in place

Restriction: the left-hand side must be a mutable binding (let mut) — ^= assigns in place.

Bit manipulation and flags

^= flips a specific bit without needing to know its current state first — XOR-ing a bit in twice restores the original value.

const FLAG_NOTIFY: u8 = 0b0001;
const FLAG_MUTED: u8  = 0b0010;

let mut settings: u8 = FLAG_NOTIFY;
settings ^= FLAG_MUTED; // <- toggles the MUTED bit on, leaving NOTIFY untouched
settings ^= FLAG_MUTED; // toggling the same bit again restores the original value
assert_eq!(settings, FLAG_NOTIFY);

Toggling with ^= is the documented idiom on BitXorAssign for flipping a bit regardless of its current value — see += for the general notes shared across the compound-assignment operator family.

Explanation

Embedded support: Full

^= is the standard way to flip a hardware output bit without needing to know its current state first: many microcontroller GPIO ports have no dedicated "toggle" register (only the plain output-data register), so firmware reads the port's current value, XORs in the pin's bit, and writes the result back. Because XOR-ing the same bit twice restores the original value, reg ^= mask is self-inverse — calling the same toggle function twice in a row leaves the pin exactly where it started, which is exactly the behavior wanted for something like blinking an LED once per timer tick.

Usage examples

Toggling an LED pin via a read-modify-write

const GPIOA_ODR: *mut u32 = 0x4001_080C as *mut u32; // GPIOA output data register
const LED_PIN: u32 = 1 << 5;

fn toggle_led() {
    unsafe {
        let mut odr = core::ptr::read_volatile(GPIOA_ODR);
        odr ^= LED_PIN; // <- flips only the LED bit, in place
        core::ptr::write_volatile(GPIOA_ODR, odr);
    }
}