Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

wrapping add #9

Merged
merged 11 commits into from
Sep 25, 2023
Merged

wrapping add #9

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
11 commits
Select commit Hold shift + click to select a range
e8bb70b
wrapping add
Easyoakland Sep 1, 2023
c6ff5fd
Fix potential overflow by forwarding to std impl
Easyoakland Sep 5, 2023
dd5ed24
const fn, use MAX, MIN directly
Easyoakland Sep 6, 2023
d23d13f
Formatting
Easyoakland Sep 6, 2023
fba6c18
Wrapping add method that doesn't require panic on any input.
Easyoakland Sep 6, 2023
ef0d93c
Nearly done with explanation for algorithm
Easyoakland Sep 7, 2023
086928b
Fixed no_panic wrapping_add impl explanation.
Easyoakland Sep 7, 2023
db4b833
minor comment fix
Easyoakland Sep 7, 2023
66dad44
fix wrapping_add(signed::MIN) and minor formatting
Easyoakland Sep 25, 2023
210a6a8
fix fmt errors
Easyoakland Sep 25, 2023
ef0b60c
clarify safety comment
Easyoakland Sep 25, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 24 additions & 0 deletions src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -792,6 +792,30 @@ macro_rules! impl_ranged {
<Self as $crate::traits::RangeIsValid>::ASSERT;
Self::new_saturating(self.get().saturating_pow(exp))
}

/// Wrapping integer addition. Computes `self + rhs`, wrapping around the numeric
/// bounds.
#[must_use = "this returns the result of the operation, without modifying the original"]
#[inline]
pub fn wrapping_add(self, rhs: $internal) -> Self {
Easyoakland marked this conversation as resolved.
Show resolved Hide resolved
<Self as $crate::traits::RangeIsValid>::ASSERT;
Easyoakland marked this conversation as resolved.
Show resolved Hide resolved
let inner = self.get();
let range_len = Self::MAX.get().abs_diff(Self::MIN.get()) + 1;
Easyoakland marked this conversation as resolved.
Show resolved Hide resolved
let offset = rhs.rem_euclid(range_len.try_into().expect("Length of valid range is greater than the largest value in the type"));
let greater_vals = Self::MAX.get() - inner;
// No wrap
if offset <= greater_vals {
// Safety: offset <= greater_vals. No overflow.
unsafe { Self::new_unchecked(inner + offset) }
}
// Wrap
else {
// Safety:
// - offset < range_len by rem_euclid (MIN + ... safe)
// - offset > greater_values from if statement (offset - (greater_values + 1) safe)
unsafe { Self::new_unchecked(Self::MIN.get() + (offset - (greater_vals + 1))) }
}
}
}

impl<const MIN: $internal, const MAX: $internal> $optional_type<MIN, MAX> {
Expand Down
12 changes: 12 additions & 0 deletions src/tests.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -385,6 +385,18 @@ macro_rules! tests {
assert_eq!($t::<5, 10>::MAX.saturating_add(1), $t::<5, 10>::MAX);
)*}

#[test]
fn wrapping_add() {$(
Easyoakland marked this conversation as resolved.
Show resolved Hide resolved
assert_eq!($t::<5, 10>::MAX.wrapping_add(0), $t::<5, 10>::MAX);
assert_eq!($t::<5, 10>::MAX.wrapping_add(1), $t::<5, 10>::MIN);
)*
$(if_signed! { $signed
assert_eq!($t::<-5, 10>::MAX.wrapping_add(0), $t::<-5, 10>::MAX);
assert_eq!($t::<-5, 10>::MAX.wrapping_add(1), $t::<-5, 10>::MIN);
assert_eq!($t::<-5, 10>::MIN.wrapping_add(-1), $t::<-5, 10>::MAX);
})*
}

#[test]
fn saturating_sub() {$(
assert_eq!($t::<5, 10>::MIN.saturating_sub(0), $t::<5, 10>::MIN);
Expand Down