Fix checked operations documentation.

- Remove the implication that wrapping is the default behaviour for `CheckedEuclid` methods.
- Replace mentions of 'underflow' with 'overflow'.

Author: ocstl

src/ops/checked.rs

@@ -32,9 +32,9 @@ checked_impl!(CheckedAdd, checked_add, i64);
 checked_impl!(CheckedAdd, checked_add, isize);
 checked_impl!(CheckedAdd, checked_add, i128);
 
-/// Performs subtraction, returning `None` if underflow occurred.
+/// Performs subtraction, returning `None` if overflow occurred.
 pub trait CheckedSub: Sized + Sub<Self, Output = Self> {
-    /// Subtracts two numbers, checking for underflow. If underflow happens,
+    /// Subtracts two numbers, checking for overflow. If overflow happens,
     /// `None` is returned.
     fn checked_sub(&self, v: &Self) -> Option<Self>;
 }
@@ -53,11 +53,10 @@ checked_impl!(CheckedSub, checked_sub, i64);
 checked_impl!(CheckedSub, checked_sub, isize);
 checked_impl!(CheckedSub, checked_sub, i128);
 
-/// Performs multiplication, returning `None` if underflow or overflow
-/// occurred.
+/// Performs multiplication, returning `None` if overflow occurred.
 pub trait CheckedMul: Sized + Mul<Self, Output = Self> {
-    /// Multiplies two numbers, checking for underflow or overflow. If underflow
-    /// or overflow happens, `None` is returned.
+    /// Multiplies two numbers, checking for overflow. If overflow happens,
+    /// `None` is returned.
     fn checked_mul(&self, v: &Self) -> Option<Self>;
 }
 
@@ -75,10 +74,10 @@ checked_impl!(CheckedMul, checked_mul, i64);
 checked_impl!(CheckedMul, checked_mul, isize);
 checked_impl!(CheckedMul, checked_mul, i128);
 
-/// Performs division, returning `None` on division by zero or if underflow or
-/// overflow occurred.
+/// Performs division, returning `None` on division by zero or if overflow
+/// occurred.
 pub trait CheckedDiv: Sized + Div<Self, Output = Self> {
-    /// Divides two numbers, checking for underflow, overflow and division by
+    /// Divides two numbers, checking for overflow and division by
     /// zero. If any of that happens, `None` is returned.
     fn checked_div(&self, v: &Self) -> Option<Self>;
 }
@@ -98,10 +97,10 @@ checked_impl!(CheckedDiv, checked_div, isize);
 checked_impl!(CheckedDiv, checked_div, i128);
 
 /// Performs integral remainder, returning `None` on division by zero or if
-/// underflow or overflow occurred.
+/// overflow occurred.
 pub trait CheckedRem: Sized + Rem<Self, Output = Self> {
-    /// Finds the remainder of dividing two numbers, checking for underflow, overflow and division
-    /// by zero. If any of that happens, `None` is returned.
+    /// Finds the remainder of dividing two numbers, checking for overflow and
+    /// division by zero. If any of that happens, `None` is returned.
     ///
     /// # Examples
     ///

src/ops/euclid.rs

@@ -136,15 +136,16 @@ impl Euclid for f64 {
 }
 
 pub trait CheckedEuclid: Euclid {
-    /// Performs euclid division that returns `None` instead of panicking on division by zero
-    /// and instead of wrapping around on underflow and overflow.
+    /// Performs euclid division, returning `None` on division by zero or if
+    /// overflow occurred.
     fn checked_div_euclid(&self, v: &Self) -> Option<Self>;
 
-    /// Finds the euclid remainder of dividing two numbers, checking for underflow, overflow and
-    /// division by zero. If any of that happens, `None` is returned.
+    /// Finds the euclid remainder of dividing two numbers, returning `None` on
+    /// division by zero or if overflow occurred.
     fn checked_rem_euclid(&self, v: &Self) -> Option<Self>;
 
-    /// Returns both the quotient and remainder from checked Euclidean division.
+    /// Returns both the quotient and remainder from checked Euclidean division,
+    /// returning `None` on division by zero or if overflow occurred.
     ///
     /// By default, it internally calls both `CheckedEuclid::checked_div_euclid` and `CheckedEuclid::checked_rem_euclid`,
     /// but it can be overridden in order to implement some optimization.