Trait sp_runtime::traits::EnsureSubAssign

source · 
pub trait EnsureSubAssign: CheckedSub + PartialOrd<Self> + Zero {
    fn ensure_sub_assign(&mut self, v: Self) -> Result<(), ArithmeticError> { ... }
}
Expand description

Performs self subtraction that returns ArithmeticError instead of wrapping around on underflow.

Provided Methods§

Subtracts two numbers overwriting the left hand one, checking for overflow.

If it fails, ArithmeticError is returned.

Examples
use sp_arithmetic::traits::EnsureSubAssign;

let mut a: i32 = 10;
let b: i32 = 20;

a.ensure_sub_assign(b).unwrap();
assert_eq!(a, -10);
use sp_arithmetic::{traits::EnsureSubAssign, ArithmeticError};

fn underflow() -> Result<(), ArithmeticError> {
    let mut zero: u32 = 0;
    zero.ensure_sub_assign(1)?;
    Ok(())
}

fn overflow() -> Result<(), ArithmeticError> {
    let mut zero = i32::MAX;
    zero.ensure_sub_assign(-1)?;
    Ok(())
}

assert_eq!(underflow(), Err(ArithmeticError::Underflow));
assert_eq!(overflow(), Err(ArithmeticError::Overflow));

Implementors§