Trait Truncate

Source

pub trait Truncate: Integer {
    // Required methods
    fn truncate<T>(self) -> T
       where Self: TruncateTarget<T>;
    fn saturating_truncate<T>(self) -> T
       where Self: TruncateTarget<T>;
    fn checked_truncate<T>(self) -> Option<T>
       where Self: TruncateTarget<T>;
}

Expand description

Truncate to an integer of the same size or smaller.

Preserve the least significant bits with .truncate():

assert_eq!(u16::MAX.truncate::<u8>(), u8::MAX);
assert_eq!(u32::MAX.truncate::<u16>(), u16::MAX);
assert_eq!(u64::MAX.truncate::<u32>(), u32::MAX);
assert_eq!(u128::MAX.truncate::<u64>(), u64::MAX);

assert_eq!((-1_i16).truncate::<i8>(), -1_i8);
assert_eq!((-1_i32).truncate::<i16>(), -1_i16);
assert_eq!((-1_i64).truncate::<i32>(), -1_i32);
assert_eq!((-1_i128).truncate::<i64>(), -1_i64);

Saturate to the numeric bounds with .saturating_truncate():

assert_eq!(500_u16.saturating_truncate::<u8>(), u8::MAX);
assert_eq!(u32::MAX.saturating_truncate::<u16>(), u16::MAX);
assert_eq!(u64::MAX.saturating_truncate::<u32>(), u32::MAX);
assert_eq!(u128::MAX.saturating_truncate::<u64>(), u64::MAX);

assert_eq!((-500_i16).saturating_truncate::<i8>(), i8::MIN);
assert_eq!(i32::MIN.saturating_truncate::<i16>(), i16::MIN);
assert_eq!(i64::MIN.saturating_truncate::<i32>(), i32::MIN);
assert_eq!(i128::MIN.saturating_truncate::<i64>(), i64::MIN);

Checked with .checked_truncate(), returning None if the value is out of range:

assert_eq!(u16::MAX.checked_truncate::<u8>(), None);
assert_eq!(u32::MAX.checked_truncate::<u16>(), None);
assert_eq!(u64::MAX.checked_truncate::<u32>(), None);
assert_eq!(u128::MAX.checked_truncate::<u64>(), None);

assert_eq!(i16::MIN.checked_truncate::<i8>(), None);
assert_eq!(i32::MIN.checked_truncate::<i16>(), None);
assert_eq!(i64::MIN.checked_truncate::<i32>(), None);
assert_eq!(i128::MIN.checked_truncate::<i64>(), None);