Trait polkadot_service::runtime_traits::EnsureSub

pub trait EnsureSub: EnsureSubAssign {
    // Provided method
    fn ensure_sub(self, v: Self) -> Result<Self, ArithmeticError> { ... }
}

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

Provided Methods

fn ensure_sub(self, v: Self) -> Result<Self, ArithmeticError>

Subtracts two numbers, checking for overflow.

If it fails, ArithmeticError is returned.

Similar to CheckedSub::checked_sub() but returning an ArithmeticError error.

Examples

use sp_arithmetic::traits::EnsureSub;

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

assert_eq!(a.ensure_sub(b), Ok(-10));

use sp_arithmetic::{traits::EnsureSub, ArithmeticError};

fn underflow() -> Result<(), ArithmeticError> {
    0u32.ensure_sub(1)?;
    Ok(())
}

fn overflow() -> Result<(), ArithmeticError> {
    i32::MAX.ensure_sub(-1)?;
    Ok(())
}

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

Object Safety

This trait is not object safe.

Implementors

impl<T> EnsureSub for T

where T: EnsureSubAssign,